【home88一必发】PE结构分析,能源表结构

by admin on 2019年3月9日

财富表是三个树形结构,能够安装成2的三11次方的层数,Windows 使用了3级:

能源表是3个树形结构,能够设置成2的33回方的层数,Windows 使用了3级:

[PE结构分析] 11.财富表结构,pe结构

能源表是三个树形结构,能够安装成2的三十一次方的层数,Windows 使用了3级:

类型->名称->语言

 

在这之中涉嫌到多少个协会:

 

Data

Description

Resource Directory Tables (and Resource Directory Entries)

A series of tables, one for each group of nodes in the tree. All top-level (Type) nodes are listed in the first table. Entries in this table point to second-level tables. Each second-level tree has the same Type ID but different Name IDs. Third-level trees have the same Type and Name IDs but different Language IDs.

Each individual table is immediately followed by directory entries, in which each entry has a name or numeric identifier and a pointer to a data description or a table at the next lower level.

Resource Directory Strings

Two-byte-aligned Unicode strings, which serve as string data that is pointed to by directory entries.

Resource Data Description

An array of records, pointed to by tables, that describe the actual size and location of the resource data. These records are the leaves in the resource-description tree.

Resource Data

Raw data of the resource section. The size and location information in the Resource Data Descriptions field delimit the individual regions of resource data.

 

 

 

 

The Portable Executable File Format from Top to Bottom

Randy Kath
Microsoft Developer Network Technology Group

Created: June 12, 1993

 

Click to open or copy the files in the EXEVIEW sample application for
this technical article.

Click to open or copy the files in the PEFILE sample application for
this technical article.

类型->名称->语言

类型->名称->语言

Resource Directory Table

Each resource directory table has the following format. This data
structure should be considered the heading of a table because the table
actually consists of directory entries (described in section 6.9.2,
“Resource Directory Entries”) and this structure:

Offset

Size

Field

Description

  0

4

Characteristics

Resource flags. This field is reserved for future use. It is currently set to zero.

  4

4

Time/Date Stamp

The time that the resource data was created by the resource compiler.

  8

2

Major Version

The major version number, set by the user.

10

2

Minor Version

The minor version number, set by the user.

12

2

Number of Name Entries

The number of directory entries immediately following the table that use strings to identify Type, Name, or Language entries (depending on the level of the table).

14

2

Number of ID Entries

The number of directory entries immediately following the Name entries that use numeric IDs for Type, Name, or Language entries.

Abstract

The Windows NT™ version 3.1 operating system introduces a new executable
file format called the Portable Executable (PE) file format. The
Portable Executable File Format specification, though rather vague, has
been made available to the public and is included on the Microsoft
Developer Network CD (Specs and Strategy, Specifications, Windows NT
File Format Specifications).

Yet this specification alone does not provide enough information to make
it easy, or even reasonable, for developers to understand the PE file
format. This article is meant to address that problem. In it you’ll find
a thorough explanation of the entire PE file format, along with
descriptions of all the necessary structures and source code examples
that demonstrate how to use this information.

All of the source code examples that appear in this article are taken
from a dynamic-link library (DLL) called PEFILE.DLL. I wrote this DLL
simply for the purpose of getting at the important information contained
within a PE file. The DLL and its source code are also included on this
CD as part of the PEFile sample application; feel free to use the DLL in
your own applications. Also, feel free to take the source code and build
on it for any specific purpose you may have. At the end of this article,
you’ll find a brief list of the functions exported from the PEFILE.DLL
and an explanation of how to use them. I think you’ll find these
functions make understanding the PE file format easier to cope with.

home88一必发 1

home88一必发 2

 

Introduction

The recent addition of the Microsoft® Windows NT™ operating system to
the family of Windows™ operating systems brought many changes to the
development environment and more than a few changes to applications
themselves. One of the more significant changes is the introduction of
the Portable Executable (PE) file format. The new PE file format draws
primarily from the COFF (Common Object File Format) specification that
is common to UNIX® operating systems. Yet, to remain compatible with
previous versions of the MS-DOS® and Windows operating systems, the PE
file format also retains the old familiar MZ header from MS-DOS.

In this article, the PE file format is explained using a top-down
approach. This article discusses each of the components of the file as
they occur when you traverse the file’s contents, starting at the top
and working your way down through the file.

Much of the definition of individual file components comes from the file
WINNT.H, a file included in the Microsoft Win32™ Software Development
Kit (SDK) for Windows NT. In it you will find structure type definitions
for each of the file headers and data directories used to represent
various components in the file. In other places in the file, WINNT.H
lacks sufficient definition of the file structure. In these places, I
chose to define my own structures that can be used to access the data
from the file. You will find these structures defined in PEFILE.H, a
file used to create the PEFILE.DLL. The entire suite of PEFILE.H
development files is included in the PEFile sample application.

In addition to the PEFILE.DLL sample code, a separate Win32-based sample
application called EXEVIEW.EXE accompanies this article. This sample was
created for two purposes: First, I needed a way to be able to test the
PEFILE.DLL functions, which in some cases required multiple file views
simultaneously—hence the multiple view support. Second, much of the work
of figuring out PE file format involved being able to see the data
interactively. For example, to understand how the import address name
table is structured, I had to view the .idata section header, the import
image data directory, the optional header, and the actual .idata section
body, all simultaneously. EXEVIEW.EXE is the perfect sample for viewing
that information.

Without further ado, let’s begin.

 

 

Resource Directory Entries

The directory entries make up the rows of a table. Each resource
directory entry has the following format. Whether the entry is a Name or
ID entry is indicated by the resource directory table, which indicates
how many Name and ID entries follow it (remember that all the Name
entries precede all the ID entries for the table). All entries for the
table are sorted in ascending order: the Name entries by case-sensitive
string and the ID entries by numeric value.  Offsets are relative to the
address in the IMAGE_DIRECTORY_ENTRY_RESOURCE DataDirectory.

Offset

Size

Field

Description

0

4

Name Offset

The offset of a string that gives the Type, Name, or Language ID entry, depending on level of table.

0

4

Integer ID

A 32-bit integer that identifies the Type, Name, or Language ID entry.

4

4

Data Entry Offset

High bit 0. Address of a Resource Data entry (a leaf).

4

4

Subdirectory Offset

High bit 1. The lower 31 bits are the address of another resource directory table (the next level down).

Structure of PE Files

The PE file format is organized as a linear stream of data. It begins
with an MS-DOS header, a real-mode program stub, and a PE file
signature. Immediately following is a PE file header and optional
header. Beyond that, all the section headers appear, followed by all of
the section bodies. Closing out the file are a few other regions of
miscellaneous information, including relocation information, symbol
table information, line number information, and string table data. All
of this is more easily absorbed by looking at it graphically, as shown
in Figure 1.

home88一必发 3

Figure 1. Structure of a Portable Executable file image

Starting with the MS-DOS file header structure, each of the components
in the PE file format is discussed below in the order in which it occurs
in the file. Much of this discussion is based on sample code that
demonstrates how to get to the information in the file. All of the
sample code is taken from the file PEFILE.C, the source module for
PEFILE.DLL. Each of these examples takes advantage of one of the coolest
features of Windows NT, memory-mapped files. Memory-mapped files permit
the use of simple pointer dereferencing to access the data contained
within the file. Each of the examples uses memory-mapped files for
accessing data in PE files.

**Note **   Refer to the section at the end of this article for a
discussion on how to use PEFILE.DLL.

里头涉嫌到八个组织:

内部涉及到多个组织:

 

MS-DOS/Real-Mode Header

As mentioned above, the first component in the PE file format is the
MS-DOS header. The MS-DOS header is not new for the PE file format. It
is the same MS-DOS header that has been around since version 2 of the
MS-DOS operating system. The main reason for keeping the same structure
intact at the beginning of the PE file format is so that, when you
attempt to load a file created under Windows version 3.1 or earlier, or
MS DOS version 2.0 or later, the operating system can read the file and
understand that it is not compatible. In other words, when you attempt
to run a Windows NT executable on MS-DOS version 6.0, you get this
message: “This program cannot be run in DOS mode.” If the MS-DOS header
was not included as the first part of the PE file format, the operating
system would simply fail the attempt to load the file and offer
something completely useless, such as: “The name specified is not
recognized as an internal or external command, operable program or batch
file.”

The MS-DOS header occupies the first 64 bytes of the PE file. A
structure representing its content is described below:

WINNT.H

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  1. typedef struct _IMAGE_DOS_HEADER {  // DOS .EXE header  
  2.     USHORT e_magic;         // Magic number  
  3.     USHORT e_cblp;          // Bytes on last page of file  
  4.     USHORT e_cp;            // Pages in file  
  5.     USHORT e_crlc;          // Relocations  
  6.     USHORT e_cparhdr;       // Size of header in paragraphs  
  7.     USHORT e_minalloc;      // Minimum extra paragraphs needed  
  8.     USHORT e_maxalloc;      // Maximum extra paragraphs needed  
  9.     USHORT e_ss;            // Initial (relative) SS value  
  10.     USHORT e_sp;            // Initial SP value  
  11.     USHORT e_csum;          // Checksum  
  12.     USHORT e_ip;            // Initial IP value  
  13.     USHORT e_cs;            // Initial (relative) CS value  
  14.     USHORT e_lfarlc;        // File address of relocation table  
  15.     USHORT e_ovno;          // Overlay number  
  16.     USHORT e_res[4];        // Reserved words  
  17.     USHORT e_oemid;         // OEM identifier (for e_oeminfo)  
  18.     USHORT e_oeminfo;       // OEM information; e_oemid specific  
  19.     USHORT e_res2[10];      // Reserved words  
  20.     LONG   e_lfanew;        // File address of new exe header  
  21.   } IMAGE_DOS_HEADER, *PIMAGE_DOS_HEADER;  

The first field, e_magic , is the so-called magic number. This
field is used to identify an MS-DOS–compatible file type. All
MS-DOS–compatible executable files set this value to 0x54AD, which
represents the ASCII characters MZ . MS-DOS headers are sometimes
referred to as MZ headers for this reason. Many other fields are
important to MS-DOS operating systems, but for Windows NT, there is
really one more important field in this structure. The final
field, e_lfanew , is a 4-byte offset into the file where the PE
file header is located. It is necessary to use this offset to locate the
PE header in the file. For PE files in Windows NT, the PE file header
occurs soon after the MS-DOS header with only the real-mode stub program
between them.

 

 

Resource Directory String

The resource directory string area consists of Unicode strings, which
are word-aligned. These strings are stored together after the last
Resource Directory entry and before the first Resource Data entry. This
minimizes the impact of these variable-length strings on the alignment
of the fixed-size directory entries. Each resource directory string has
the following format:

Offset

Size

Field

Description

0

2

Length

The size of the string, not including length field itself.

2

variable

Unicode String

The variable-length Unicode string data, word-aligned.

Real-Mode Stub Program

The real-mode stub program is an actual program run by MS-DOS when the
executable is loaded. For an actual MS-DOS executable image file, the
application begins executing here. For successive operating systems,
including Windows, OS/2®, and Windows NT, an MS-DOS stub program is
placed here that runs instead of the actual application. The programs
typically do no more than output a line of text, such as: “This program
requires Microsoft Windows v3.1 or greater.” Of course, whoever creates
the application is able to place any stub they like here, meaning you
may often see such things as: “You can’t run a Windows NT application on
OS/2, it’s simply not possible.”

When building an application for Windows version 3.1, the linker links a
default stub program called WINSTUB.EXE into your executable. You can
override the default linker behavior by substituting your own valid
MS-DOS–based program in place of WINSTUB and indicating this to the
linker with the STUB module definition statement. Applications
developed for Windows NT can do the same thing by using the -STUB:
linker
 option when linking the executable file.

Data

Description

Resource Directory Tables (and Resource Directory Entries)

A series of tables, one for each group of nodes in the tree. All top-level (Type) nodes are listed in the first table. Entries in this table point to second-level tables. Each second-level tree has the same Type ID but different Name IDs. Third-level trees have the same Type and Name IDs but different Language IDs.

Each individual table is immediately followed by directory entries, in which each entry has a name or numeric identifier and a pointer to a data description or a table at the next lower level.

Resource Directory Strings

Two-byte-aligned Unicode strings, which serve as string data that is pointed to by directory entries.

Resource Data Description

An array of records, pointed to by tables, that describe the actual size and location of the resource data. These records are the leaves in the resource-description tree.

Resource Data

Raw data of the resource section. The size and location information in the Resource Data Descriptions field delimit the individual regions of resource data.

Data

Description

Resource Directory Tables (and Resource Directory Entries)

A series of tables, one for each group of nodes in the tree. All top-level (Type) nodes are listed in the first table. Entries in this table point to second-level tables. Each second-level tree has the same Type ID but different Name IDs. Third-level trees have the same Type and Name IDs but different Language IDs.

Each individual table is immediately followed by directory entries, in which each entry has a name or numeric identifier and a pointer to a data description or a table at the next lower level.

Resource Directory Strings

Two-byte-aligned Unicode strings, which serve as string data that is pointed to by directory entries.

Resource Data Description

An array of records, pointed to by tables, that describe the actual size and location of the resource data. These records are the leaves in the resource-description tree.

Resource Data

Raw data of the resource section. The size and location information in the Resource Data Descriptions field delimit the individual regions of resource data.

 

PE File Header and Signature

The PE file header is located by indexing the e_lfanew field of the
MS-DOS header. The e_lfanew field simply gives the offset in the
file, so add the file’s memory-mapped base address to determine the
actual memory-mapped address. For example, the following macro is
included in the PEFILE.H source file:

 

 

Resource Data Entry

Each Resource Data entry describes an actual unit of raw data in the
Resource Data area. A Resource Data entry has the following format:

Offset

Size

Field

Description

  0

4

Data RVA

The address of a unit of resource data in the Resource Data area.

  4

4

Size

The size, in bytes, of the resource data that is pointed to by the Data RVA field.

  8

4

Codepage

The code page that is used to decode code point values within the resource data. Typically, the code page would be the Unicode code page.

12

4

Reserved, must be 0.

] 11.财富表结构,pe结构
财富表是一个树形结构,能够安装成2的三10遍方的层数,Windows 使用了3级:
类型-名称-语言 在那之中涉及到四…

PEFILE.H

#define NTSIGNATURE(a) ((LPVOID)((BYTE *)a +    /
                        ((PIMAGE_DOS_HEADER)a)->e_lfanew))

When manipulating PE file information, I found that there were several
locations in the file that I needed to refer to often. Since these
locations are merely offsets into the file, it is easier to implement
these locations as macros because they provide much better performance
than functions do.

Notice that instead of retrieving the offset of the PE file header, this
macro retrieves the location of the PE file signature. Starting with
Windows and OS/2 executables, .EXE files were given file signatures to
specify the intended target operating system. For the PE file format in
Windows NT, this signature occurs immediately before the PE file header
structure. In versions of Windows and OS/2, the signature is the first
word of the file header. Also, for the PE file format, Windows NT uses a
DWORD for the signature.

The macro presented above returns the offset of where the file signature
appears, regardless of which type of executable file it is. So depending
on whether it’s a Windows NT file signature or not, the file header
exists either after the signature DWORD or at the signature WORD. To
resolve this confusion, I wrote the ImageFileType function
(following), which returns the type of image file:

 

 

PEFILE.C

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  1. DWORD  WINAPI ImageFileType (  
  2.     LPVOID    lpFile)  
  3. {  
  4.     /* DOS file signature comes first. */  
  5.     if (*(USHORT *)lpFile == IMAGE_DOS_SIGNATURE)  
  6.         {  
  7.         /* Determine location of PE File header from  
  8. 【home88一必发】PE结构分析,能源表结构。           DOS header. */  
  9.         if (LOWORD (*(DWORD *)NTSIGNATURE (lpFile)) ==  
  10.                                 IMAGE_OS2_SIGNATURE ||  
  11.             LOWORD (*(DWORD *)NTSIGNATURE (lpFile)) ==  
  12.                              IMAGE_OS2_SIGNATURE_LE)  
  13.             return (DWORD)LOWORD(*(DWORD *)NTSIGNATURE (lpFile));  
  14.   
  15.         else if (*(DWORD *)NTSIGNATURE (lpFile) ==  
  16.                             IMAGE_NT_SIGNATURE)  
  17.             return IMAGE_NT_SIGNATURE;  
  18.   
  19.         else  
  20.             return IMAGE_DOS_SIGNATURE;  
  21.         }  
  22.   
  23.     else  
  24.         /* unknown file type */  
  25.         return 0;  
  26. }  

The code listed above quickly shows how useful the NTSIGNATURE macro
becomes. The macro makes it easy to compare the different file types and
return the appropriate one for a given type of file. The four different
file types defined in WINNT.H are:

 

 

WINNT.H

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  1. #define IMAGE_DOS_SIGNATURE             0x5A4D      // MZ  
  2. #define IMAGE_OS2_SIGNATURE             0x454E      // NE  
  3. #define IMAGE_OS2_SIGNATURE_LE          0x454C      // LE  
  4. #define IMAGE_NT_SIGNATURE              0x00004550  // PE00  

At first it seems curious that Windows executable file types do not
appear on this list. But then, after a little investigation, the reason
becomes clear: There really is no difference between Windows executables
and OS/2 executables other than the operating system version
specification. Both operating systems share the same executable file
structure.

Turning our attention back to the Windows NT PE file format, we find
that once we have the location of the file signature, the PE file
follows four bytes later. The next macro identifies the PE file header:

 

 

PEFILE.C

#define PEFHDROFFSET(a) ((LPVOID)((BYTE *)a +  /
    ((PIMAGE_DOS_HEADER)a)->e_lfanew + SIZE_OF_NT_SIGNATURE))

The only difference between this and the previous macro is that this one
adds in the constant SIZE_OF_NT_SIGNATURE. Sad to say, this constant
is not defined in WINNT.H, but is instead one I defined in PEFILE.H as
the size of a DWORD.

Now that we know the location of the PE file header, we can examine the
data in the header simply by assigning this location to a structure, as
in the following example:

PIMAGE_FILE_HEADER   pfh;

pfh = (PIMAGE_FILE_HEADER)PEFHDROFFSET (lpFile);

I n this example, lpFile represents a pointer to the base of the
memory-mapped executable file, and therein lies the convenience of
memory-mapped files. No file I/O needs to be performed; simply
dereference the pointer pfh to access information in the file. The PE
file header structure is defined as:

Resource Directory Table

Each resource directory
table has the following format. This data structure should be considered
the heading of a table because the table actually consists of directory
entries (described in section 6.9.2, “Resource Directory Entries”) and
this structure:

Offset Size Field Description
0 4 Characteristics Resource flags. This field is reserved for future use. It is currently set to zero.
4 4 Time/Date Stamp The time that the resource data was created by the resource compiler.
8 2 Major Version The major version number, set by the user.
10 2 Minor Version The minor version number, set by the user.
12 2 Number of Name Entries The number of directory entries immediately following the table that use strings to identify Type, Name, or Language entries (depending on the level of the table).
14 2 Number of ID Entries The number of directory entries immediately following the Name entries that use numeric IDs for Type, Name, or Language entries.

 

Resource Directory Table

Each resource directory
table has the following format. This data structure should be considered
the heading of a table because the table actually consists of directory
entries (described in section 6.9.2, “Resource Directory Entries”) and
this structure:

Offset Size Field Description
0 4 Characteristics Resource flags. This field is reserved for future use. It is currently set to zero.
4 4 Time/Date Stamp The time that the resource data was created by the resource compiler.
8 2 Major Version The major version number, set by the user.
10 2 Minor Version The minor version number, set by the user.
12 2 Number of Name Entries The number of directory entries immediately following the table that use strings to identify Type, Name, or Language entries (depending on the level of the table).
14 2 Number of ID Entries The number of directory entries immediately following the Name entries that use numeric IDs for Type, Name, or Language entries.

 

WINNT.H

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  1. typedef struct _IMAGE_FILE_HEADER {  
  2.     USHORT  Machine;  
  3.     USHORT  NumberOfSections;  
  4.     ULONG   TimeDateStamp;  
  5.     ULONG   PointerToSymbolTable;  
  6.     ULONG   NumberOfSymbols;  
  7.     USHORT  SizeOfOptionalHeader;  
  8.     USHORT  Characteristics;  
  9. } IMAGE_FILE_HEADER, *PIMAGE_FILE_HEADER;  
  10.   
  11. #define IMAGE_SIZEOF_FILE_HEADER             20  

Notice that the size of the file header structure is conveniently
defined in the include file. This makes it easy to get the size of the
structure, but I found it easier to use the sizeof function on the
structure itself because it does not require me to remember the name of
the constant IMAGE_SIZEOF_FILE_HEADER in addition to
the IMAGE_FILE_HEADER structure name itself. On the other hand,
remembering the name of all the structures proved challenging enough,
especially since none of these structures is documented anywhere except
in the WINNT.H include file.

The information in the PE file is basically high-level information that
is used by the system or applications to determine how to treat the
file. The first field is used to indicate what type of machine the
executable was built for, such as the DEC® Alpha, MIPS R4000, Intel®
x86, or some other processor. The system uses this information to
quickly determine how to treat the file before going any further into
the rest of the file data.

The Characteristics field identifies specific characteristics about
the file. For example, consider how separate debug files are managed for
an executable. It is possible to strip debug information from a PE file
and store it in a debug file (.DBG) for use by debuggers. To do this, a
debugger needs to know whether to find the debug information in a
separate file or not and whether the information has been stripped from
the file or not. A debugger could find out by drilling down into the
executable file looking for debug information. To save the debugger from
having to search the file, a file characteristic that indicates that the
file has been stripped (IMAGE_FILE_DEBUG_STRIPPED) was invented.
Debuggers can look in the PE file header to quickly determine whether
the debug information is present in the file or not.

WINNT.H defines several other flags that indicate file header
information much the way the example described above does. I’ll leave it
as an exercise for the reader to look up the flags to see if any of them
are interesting or not. They are located in WINNT.H immediately after
the IMAGE_FILE_HEADER structure described above.

One other useful entry in the PE file header structure is
the NumberOfSections field. It turns out that you need to know how
many sections—more specifically, how many section headers and section
bodies—are in the file in order to extract the information easily. Each
section header and section body is laid out sequentially in the file, so
the number of sections is necessary to determine where the section
headers and bodies end. The following function extracts the number of
sections from the PE file header:

Resource Directory Entries

The directory entries
make up the rows of a table. Each resource directory entry has the
following format. Whether the entry is a Name or ID entry is indicated
by the resource directory table, which indicates how many Name and ID
entries follow it (remember that all the Name entries precede all the ID
entries for the table). All entries for the table are sorted in
ascending order: the Name entries by case-sensitive string and the ID
entries by numeric value.  Offsets are relative to the address in the
IMAGE_DIRECTORY_ENTRY_RESOURCE DataDirectory.

Offset

Size

Field

Description

0

4

Name Offset

The offset of a string that gives the Type, Name, or Language ID entry, depending on level of table.

0

4

Integer ID

A 32-bit integer that identifies the Type, Name, or Language ID entry.

4

4

Data Entry Offset

High bit 0. Address of a Resource Data entry (a leaf).

4

4

Subdirectory Offset

High bit 1. The lower 31 bits are the address of another resource directory table (the next level down).

Resource Directory Entries

The directory entries
make up the rows of a table. Each resource directory entry has the
following format. Whether the entry is a Name or ID entry is indicated
by the resource directory table, which indicates how many Name and ID
entries follow it (remember that all the Name entries precede all the ID
entries for the table). All entries for the table are sorted in
ascending order: the Name entries by case-sensitive string and the ID
entries by numeric value.  Offsets are relative to the address in the
IMAGE_DIRECTORY_ENTRY_RESOURCE DataDirectory.

Offset

Size

Field

Description

0

4

Name Offset

The offset of a string that gives the Type, Name, or Language ID entry, depending on level of table.

0

4

Integer ID

A 32-bit integer that identifies the Type, Name, or Language ID entry.

4

4

Data Entry Offset

High bit 0. Address of a Resource Data entry (a leaf).

4

4

Subdirectory Offset

High bit 1. The lower 31 bits are the address of another resource directory table (the next level down).

PEFILE.C

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  1. int   WINAPI NumOfSections (  
  2.     LPVOID    lpFile)  
  3. {  
  4.     /* Number of sections is indicated in file header. */  
  5.     return (int)((PIMAGE_FILE_HEADER)  
  6.                   PEFHDROFFSET (lpFile))->NumberOfSections);  
  7. }  

As you can see, the PEFHDROFFSET and the other macros are pretty
handy to have around.

 

 

PE Optional Header

The next 224 bytes in the executable file make up the PE optional
header. Though its name is “optional header,” rest assured that this is
not an optional entry in PE executable files. A pointer to the optional
header is obtained with the OPTHDROFFSET macro:

Resource Directory String

The resource directory
string area consists of Unicode strings, which are word-aligned. These
strings are stored together after the last Resource Directory entry and
before the first Resource Data entry. This minimizes the impact of these
variable-length strings on the alignment of the fixed-size directory
entries. Each resource directory string has the following format:

Offset

Size

Field

Description

0

2

Length

The size of the string, not including length field itself.

2

variable

Unicode String

The variable-length Unicode string data, word-aligned.

Resource Directory String

The resource directory
string area consists of Unicode strings, which are word-aligned. These
strings are stored together after the last Resource Directory entry and
before the first Resource Data entry. This minimizes the impact of these
variable-length strings on the alignment of the fixed-size directory
entries. Each resource directory string has the following format:

Offset

Size

Field

Description

0

2

Length

The size of the string, not including length field itself.

2

variable

Unicode String

The variable-length Unicode string data, word-aligned.

PEFILE.H

#define OPTHDROFFSET(a) ((LPVOID)((BYTE *)a                 + /
    ((PIMAGE_DOS_HEADER)a)->e_lfanew + SIZE_OF_NT_SIGNATURE + /
    sizeof (IMAGE_FILE_HEADER)))

The optional header contains most of the meaningful information about
the executable image, such as initial stack size, program entry point
location, preferred base address, operating system version, section
alignment information, and so forth.
The IMAGE_OPTIONAL_HEADER structure represents the optional header
as follows:

 

 

WINNT.H

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  1. typedef struct _IMAGE_OPTIONAL_HEADER {  
  2.     //  
  3.     // Standard fields.  
  4.     //  
  5.     USHORT  Magic;  
  6.     UCHAR   MajorLinkerVersion;  
  7.     UCHAR   MinorLinkerVersion;  
  8.     ULONG   SizeOfCode;  
  9.     ULONG   SizeOfInitializedData;  
  10.     ULONG   SizeOfUninitializedData;  
  11.     ULONG   AddressOfEntryPoint;  
  12.     ULONG   BaseOfCode;  
  13.     ULONG   BaseOfData;  
  14.     //  
  15.     // NT additional fields.  
  16.     //  
  17.     ULONG   ImageBase;  
  18.     ULONG   SectionAlignment;  
  19.     ULONG   FileAlignment;  
  20.     USHORT  MajorOperatingSystemVersion;  
  21.     USHORT  MinorOperatingSystemVersion;  
  22.     USHORT  MajorImageVersion;  
  23.     USHORT  MinorImageVersion;  
  24.     USHORT  MajorSubsystemVersion;  
  25.     USHORT  MinorSubsystemVersion;  
  26. 【home88一必发】PE结构分析,能源表结构。    ULONG   Reserved1;  
  27.     ULONG   SizeOfImage;  
  28.     ULONG   SizeOfHeaders;  
  29.     ULONG   CheckSum;  
  30.     USHORT  Subsystem;  
  31.     USHORT  DllCharacteristics;  
  32.     ULONG   SizeOfStackReserve;  
  33.     ULONG   SizeOfStackCommit;  
  34.     ULONG   SizeOfHeapReserve;  
  35.     ULONG   SizeOfHeapCommit;  
  36.     ULONG   LoaderFlags;  
  37.     ULONG   NumberOfRvaAndSizes;  
  38.     IMAGE_DATA_DIRECTORY DataDirectory[IMAGE_NUMBEROF_DIRECTORY_ENTRIES];  
  39. } IMAGE_OPTIONAL_HEADER, *PIMAGE_OPTIONAL_HEADER;  

As you can see, the list of fields in this structure is rather lengthy.
Rather than bore you with descriptions of all of these fields, I’ll
simply discuss the useful ones—that is, useful in the context of
exploring the PE file format.

Resource Data Entry

Each Resource Data
entry describes an actual unit of raw data in the Resource Data area. A
Resource Data entry has the following format:

Offset

Size

Field

Description

  0

4

Data RVA

The address of a unit
of resource data in the Resource Data area.

  4

4

Size

The size, in bytes, of
the resource data that is pointed to by the Data RVA field.

  8

4

Codepage

The code page that is
used to decode code point values within the resource data. Typically,
the code page would be the Unicode code page.

12

4

Reserved, must be
0.

Resource Data Entry

Each Resource Data
entry describes an actual unit of raw data in the Resource Data area. A
Resource Data entry has the following format:

Offset

Size

Field

Description

  0

4

Data RVA

The address of a unit
of resource data in the Resource Data area.

  4

4

Size

The size, in bytes, of
the resource data that is pointed to by the Data RVA field.

  8

4

Codepage

The code page that is
used to decode code point values within the resource data. Typically,
the code page would be the Unicode code page.

12

4

Reserved, must be
0.

Standard Fields

First, note that the structure is divided into “Standard fields” and “NT
additional fields.” The standard fields are those common to the Common
Object File Format (COFF), which most UNIX executable files use. Though
the standard fields retain the names defined in COFF, Windows NT
actually uses some of them for different purposes that would be better
described with other names.

  • Magic . I was unable to track down what this field is used for.
    For the EXEVIEW.EXE sample application, the value is 0x010B or 267.
  • MajorLinkerVersion , MinorLinkerVersion . Indicates version of
    the linker that linked this image. The preliminary Windows NT
    Software Development Kit (SDK), which shipped with build 438 of
    Windows NT, includes linker version 2.39 (2.27 hex).
  • SizeOfCode . Size of executable code.
  • SizeOfInitializedData . Size of initialized data.
  • SizeOfUninitializedData . Size of uninitialized data.
  • AddressOfEntryPoint . Of the standard fields,
    the AddressOfEntryPoint field is the most interesting for the PE
    file format. This field indicates the location of the entry point
    for the application and, perhaps more importantly to system hackers,
    the location of the end of the Import Address Table (IAT). The
    following function demonstrates how to retrieve the entry point of a
    Windows NT executable image from the optional header.

PEFILE.C

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  1. LPVOID  WINAPI GetModuleEntryPoint (  
  2.     LPVOID    lpFile)  
  3. {  
  4.     PIMAGE_OPTIONAL_HEADER   poh;  
  5.   
  6.     poh = (PIMAGE_OPTIONAL_HEADER)OPTHDROFFSET (lpFile);  
  7.   
  8.     if (poh != NULL)  
  9.         return (LPVOID)poh->AddressOfEntryPoint;  
  10.     else  
  11.         return NULL;  
  12. }  
  • BaseOfCode . Relative offset of code (“.text” section) in loaded
    image.
  • BaseOfData . Relative offset of uninitialized data (“.bss”
    section) in loaded image.

Windows NT Additional Fields

The additional fields added to the Windows NT PE file format provide
loader support for much of the Windows NT–specific process behavior.
Following is a summary of these fields.

  • ImageBase . Preferred base address in the address space of a
    process to map the executable image to. The linker that comes with
    the Microsoft Win32 SDK for Windows NT defaults to 0x00400000, but
    you can override the default with the -BASE: linker switch.
  • SectionAlignment . Each section is loaded into the address space
    of a process sequentially, beginning
    at ImageBase . SectionAlignment dictates the minimum amount of
    space a section can occupy when loaded—that is, sections are aligned
    on SectionAlignment boundaries.

    Section alignment can be no less than the page size (currently 4096
    bytes on the x 86 platform) and must be a multiple of the page
    size as dictated by the behavior of Windows NT’s virtual memory
    manager. 4096 bytes is the x 86 linker default, but this can be
    set using the -ALIGN: linker switch.

  • FileAlignment . Minimum granularity of chunks of information
    within the image file prior to loading. For example, the linker
    zero-pads a section body (raw data for a section) up to the
    nearest FileAlignment boundary in the file. Version 2.39 of the
    linker mentioned earlier aligns image files on a 0x200-byte
    granularity. This value is constrained to be a power of 2 between
    512 and 65,535.

  • MajorOperatingSystemVersion . Indicates the major version of the
    Windows NT operating system, currently set to 1 for Windows NT
    version 1.0.
  • MinorOperatingSystemVersion . Indicates the minor version of the
    Windows NT operating system, currently set to 0 for Windows NT
    version 1.0
  • MajorImageVersion . Used to indicate the major version number of
    the application; in Microsoft Excel version 4.0, it would be 4.
  • MinorImageVersion . Used to indicate the minor version number of
    the application; in Microsoft Excel version 4.0, it would be 0.
  • MajorSubsystemVersion . Indicates the Windows NT Win32 subsystem
    major version number, currently set to 3 for Windows NT version
    3.10.
  • MinorSubsystemVersion . Indicates the Windows NT Win32 subsystem
    minor version number, currently set to 10 for Windows NT version
    3.10.
  • Reserved1 . Unknown purpose, currently not used by the system and
    set to zero by the linker.
  • SizeOfImage . Indicates the amount of address space to reserve in
    the address space for the loaded executable image. This number is
    influenced greatly by SectionAlignment . For example, consider a
    system having a fixed page size of 4096 bytes. If you have an
    executable with 11 sections, each less than 4096 bytes, aligned on a
    65,536-byte boundary, the SizeOfImage field would be set to 11 *
    65,536 = 720,896 (176 pages). The same file linked with 4096-byte
    alignment would result in 11 * 4096 = 45,056 (11 pages) for
    the SizeOfImage field. This is a simple example in which each
    section requires less than a page of memory. In reality, the linker
    determines the exact SizeOfImage by figuring each section
    individually. It first determines how many bytes the section
    requires, then it rounds up to the nearest page boundary, and
    finally it rounds page count to the
    nearest SectionAlignment boundary. The total is then the sum of
    each section’s individual requirement.
  • SizeOfHeaders . This field indicates how much space in the file is
    used for representing all the file headers, including the MS-DOS
    header, PE file header, PE optional header, and PE section headers.
    The section bodies begin at this location in the file.
  • CheckSum . A checksum value is used to validate the executable
    file at load time. The value is set and verified by the linker. The
    algorithm used for creating these checksum values is proprietary
    information and will not be published.
  • Subsystem . Field used to identify the target subsystem for this
    executable. Each of the possible subsystem values are listed in the
    WINNT.H file immediately after
    the IMAGE_OPTIONAL_HEADER structure.
  • DllCharacteristics . Flags used to indicate if a DLL image
    includes entry points for process and thread initialization and
    termination.
  • SizeOfStackReserve , SizeOfStackCommit , SizeOfHeapReserve , SizeOfHeapCommit .
    These fields control the amount of address space to reserve and
    commit for the stack and default heap. Both the stack and heap have
    default values of 1 page committed and 16 pages reserved. These
    values are set with the linker
    switches -STACKSIZE: and -HEAPSIZE: .
  • LoaderFlags . Tells the loader whether to break on load, debug on
    load, or the default, which is to let things run normally.
  • NumberOfRvaAndSizes . This field identifies the length of
    the DataDirectory array that follows. It is important to note that
    this field is used to identify the size of the array, not the number
    of valid entries in the array.
  • DataDirectory . The data directory indicates where to find other
    important components of executable information in the file. It is
    really nothing more than an array
    of IMAGE_DATA_DIRECTORY structures that are located at the end
    of the optional header structure. The current PE file format defines
    16 possible data directories, 11 of which are now being used.

Data Directories

As defined in WINNT.H, the data directories are:

WINNT.H

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  1. // Directory Entries  
  2.   
  3. // Export Directory  
  4. #define IMAGE_DIRECTORY_ENTRY_EXPORT         0  
  5. // Import Directory  
  6. #define IMAGE_DIRECTORY_ENTRY_IMPORT         1  
  7. // Resource Directory  
  8. #define IMAGE_DIRECTORY_ENTRY_RESOURCE       2  
  9. // Exception Directory  
  10. #define IMAGE_DIRECTORY_ENTRY_EXCEPTION      3  
  11. // Security Directory  
  12. #define IMAGE_DIRECTORY_ENTRY_SECURITY       4  
  13. // Base Relocation Table  
  14. #define IMAGE_DIRECTORY_ENTRY_BASERELOC      5  
  15. // Debug Directory  
  16. #define IMAGE_DIRECTORY_ENTRY_DEBUG          6  
  17. // Description String  
  18. #define IMAGE_DIRECTORY_ENTRY_COPYRIGHT      7  
  19. // Machine Value (MIPS GP)  
  20. #define IMAGE_DIRECTORY_ENTRY_GLOBALPTR      8  
  21. // TLS Directory  
  22. #define IMAGE_DIRECTORY_ENTRY_TLS            9  
  23. // Load Configuration Directory  
  24. #define IMAGE_DIRECTORY_ENTRY_LOAD_CONFIG    10  

Each data directory is basically a structure defined as
an IMAGE_DATA_DIRECTORY . And although data directory entries
themselves are the same, each specific directory type is entirely
unique. The definition of each defined data directory is described in
“Predefined Sections” later in this article.

WINNT.H

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  1. typedef struct _IMAGE_DATA_DIRECTORY {  
  2.     ULONG   VirtualAddress;  
  3.     ULONG   Size;  
  4. } IMAGE_DATA_DIRECTORY, *PIMAGE_DATA_DIRECTORY;  

Each data directory entry specifies the size and relative virtual
address of the directory. To locate a particular directory, you
determine the relative address from the data directory array in the
optional header. Then use the virtual address to determine which section
the directory is in. Once you determine which section contains the
directory, the section header for that section is then used to find the
exact file offset location of the data directory.

So to get a data directory, you first need to know about sections, which
are described next. An example of how to locate data directories
immediately follows this discussion.

PE File Sections

The PE file specification consists of the headers defined so far and a
generic object called a section . Sections contain the content of the
file, including code, data, resources, and other executable information.
Each section has a header and a body (the raw data). Section headers are
described below, but section bodies lack a rigid file structure. They
can be organized in almost any way a linker wishes to organize them, as
long as the header is filled with enough information to be able to
decipher the data.

Section Headers

Section headers are located sequentially right after the optional header
in the PE file format. Each section header is 40 bytes with no padding
between them. Section headers are defined as in the following structure:

WINNT.H

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  1. #define IMAGE_SIZEOF_SHORT_NAME              8  
  2.   
  3. typedef struct _IMAGE_SECTION_HEADER {  
  4.     UCHAR   Name[IMAGE_SIZEOF_SHORT_NAME];  
  5.     union {  
  6.             ULONG   PhysicalAddress;  
  7.             ULONG   VirtualSize;  
  8.     } Misc;  
  9.     ULONG   VirtualAddress;  
  10.     ULONG   SizeOfRawData;  
  11.     ULONG   PointerToRawData;  
  12.     ULONG   PointerToRelocations;  
  13.     ULONG   PointerToLinenumbers;  
  14.     USHORT  NumberOfRelocations;  
  15.     USHORT  NumberOfLinenumbers;  
  16.     ULONG   Characteristics;  
  17. } IMAGE_SECTION_HEADER, *PIMAGE_SECTION_HEADER;  

How do you Go about getting section
header information for a particular section? Since section headers are
organized sequentially in no specific order, section headers must be
located by name. The following function shows how to retrieve a section
header from a PE image file given the name of the section:

PEFILE.C

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  1. BOOL    WINAPI GetSectionHdrByName (  
  2.     LPVOID                   lpFile,  
  3.     IMAGE_SECTION_HEADER     *sh,  
  4.     char                     *szSection)  
  5. {  
  6.     PIMAGE_SECTION_HEADER    psh;  
  7.     int                      nSections = NumOfSections (lpFile);  
  8.     int                      i;  
  9.   
  10.   
  11.     if ((psh = (PIMAGE_SECTION_HEADER)SECHDROFFSET (lpFile)) !=  
  12.          NULL)  
  13.         {  
  14.         /* find the section by name */  
  15.         for (i=0; i<nSections; i++)  
  16.             {  
  17.             if (!strcmp (psh->Name, szSection))  
  18.                 {  
  19.                 /* copy data to header */  
  20.                 CopyMemory ((LPVOID)sh,  
  21.                             (LPVOID)psh,  
  22.                             sizeof (IMAGE_SECTION_HEADER));  
  23.                 return TRUE;  
  24.                 }  
  25.             else  
  26.                 psh++;  
  27.             }  
  28.         }  
  29.   
  30.     return FALSE;  
  31. }  

The function simply locates the first section header via
the SECHDROFFSET macro. Then the function loops through each
section, comparing each section’s name with the name of the section it’s
looking for, until it finds the right one. When the section is found,
the function copies the data from the memory-mapped file to the
structure passed in to the function. The fields of
the IMAGE_SECTION_HEADER structure can then be accessed directly
from the structure.

Section Header Fields

  • Name . Each section header has a name field up to eight
    characters long, for which the first character must be a period.
  • PhysicalAddress or VirtualSize . The second field is a union
    field that is not currently used.
  • VirtualAddress . This field identifies the virtual address in the
    process’s address space to which to load the section. The actual
    address is created by taking the value of this field and adding it
    to the ImageBase virtual address in the optional header structure.
    Keep in mind, though, that if this image file represents a DLL,
    there is no guarantee that the DLL will be loaded to
    the ImageBase location requested. So once the file is loaded into
    a process, the actual ImageBase value should be verified
    programmatically using GetModuleHandle .
  • SizeOfRawData . This field indicates the FileAlignment -relative
    size of the section body. The actual size of the section body will
    be less than or equal to a multiple of FileAlignment in the file.
    Once the image is loaded into a process’s address space, the size of
    the section body becomes less than or equal to a multiple
    of SectionAlignment .
  • PointerToRawData . This is an offset to the location of the
    section body in the file.
  • PointerToRelocations , PointerToLinenumbers , NumberOfRelocations , NumberOfLinenumbers .
    None of these fields are used in the PE file format.
  • Characteristics . Defines the section characteristics. These
    values are found both in WINNT.H and in the Portable Executable
    Format specification located on this CD.
Value Definition
0x00000020 Code section
0x00000040 Initialized data section
0x00000080 Uninitialized data section
0x04000000 Section cannot be cached
0x08000000 Section is not pageable
0x10000000 Section is shared
0x20000000 Executable section
0x40000000 Readable section
0x80000000 Writable section

 

Locating Data Directories

Data directories exist within the body of their corresponding data
section. Typically, data directories are the first structure within the
section body, but not out of necessity. For that reason, you need to
retrieve information from both the section header and optional header to
locate a specific data directory.

To make this process easier, the following function was written to
locate the data directory for any of the directories defined in WINNT.H:

PEFILE.C

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  1. LPVOID  WINAPI ImageDirectoryOffset (  
  2.         LPVOID    lpFile,  
  3.         DWORD     dwIMAGE_DIRECTORY)  
  4. {  
  5.     PIMAGE_OPTIONAL_HEADER   poh;  
  6.     PIMAGE_SECTION_HEADER    psh;  
  7.     int                      nSections = NumOfSections (lpFile);  
  8.     int                      i = 0;  
  9.     LPVOID                   VAImageDir;  
  10.   
  11.     /* Must be 0 thru (NumberOfRvaAndSizes-1). */  
  12.     if (dwIMAGE_DIRECTORY >= poh->NumberOfRvaAndSizes)  
  13.         return NULL;  
  14.   
  15.     /* Retrieve offsets to optional and section headers. */  
  16.     poh = (PIMAGE_OPTIONAL_HEADER)OPTHDROFFSET (lpFile);  
  17.     psh = (PIMAGE_SECTION_HEADER)SECHDROFFSET (lpFile);  
  18.   
  19.     /* Locate image directory’s relative virtual address. */  
  20.     VAImageDir = (LPVOID)poh->DataDirectory  
  21.                        [dwIMAGE_DIRECTORY].VirtualAddress;  
  22.   
  23.     /* Locate section containing image directory. */  
  24.     while (i++<nSections)  
  25.         {  
  26.         if (psh->VirtualAddress <= (DWORD)VAImageDir &&  
  27.             psh->VirtualAddress +   
  28.                  psh->SizeOfRawData > (DWORD)VAImageDir)  
  29.             break;  
  30.         psh++;  
  31.         }  
  32.   
  33.     if (i > nSections)  
  34.         return NULL;  
  35.   
  36.     /* Return image import directory offset. */  
  37.     return (LPVOID)(((int)lpFile +   
  38.                      (int)VAImageDir. psh->VirtualAddress) +  
  39.                     (int)psh->PointerToRawData);  
  40. }  

The function begins by validating the requested data directory entry
number. Then it retrieves pointers to the optional header and first
section header. From the optional header, the function determines the
data directory’s virtual address, and it uses this value to determine
within which section body the data directory is located. Once the
appropriate section body has been identified, the specific location of
the data directory is found by translating the relative virtual address
of the data directory to a specific address into the file.

Predefined Sections

An application for Windows NT typically has the nine predefined sections
named .text, .bss, .rdata, .data, .rsrc, .edata, .idata, .pdata, and
.debug. Some applications do not need all of these sections, while
others may define still more sections to suit their specific needs. This
behavior is similar to code and data segments in MS-DOS and Windows
version 3.1. In fact, the way an application defines a unique section is
by using the standard compiler directives for naming code and data
segments or by using the name segment compiler option -NT —exactly
the same way in which applications defined unique code and data segments
in Windows version 3.1.

The following is a discussion of some of the more interesting sections
common to typical Windows NT PE files.

Executable code section, .text

One difference between Windows version 3.1 and Windows NT is that the
default behavior combines all code segments (as they are referred to in
Windows version 3.1) into a single section called “.text” in Windows NT.
Since Windows NT uses a page-based virtual memory management system,
there is no advantage to separating code into distinct code segments.
Consequently, having one large code section is easier to manage for both
the operating system and the application developer.

The .text section also contains the entry point mentioned earlier. The
IAT also lives in the .text section immediately before the module entry
point. (The IAT’s presence in the .text section makes sense because the
table is really a series of jump instructions, for which the specific
location to jump to is the fixed-up address.) When Windows NT executable
images are loaded into a process’s address space, the IAT is fixed up
with the location of each imported function’s physical address. In order
to find the IAT in the .text section, the loader simply locates the
module entry point and relies on the fact that the IAT occurs
immediately before the entry point. And since each entry is the same
size, it is easy to walk backward in the table to find its beginning.

Data sections, .bss, .rdata, .data

The .bss section represents uninitialized data for the application,
including all variables declared as static within a function or source
module.

The .rdata section represents read-only data, such as literal strings,
constants, and debug directory information.

All other variables (except automatic variables, which appear on the
stack) are stored in the .data section. Basically, these are application
or module global variables.

Resources section, .rsrc

The .rsrc section contains resource information for a module. It begins
with a resource directory structure like most other sections, but this
section’s data is further structured into a resource tree.
The IMAGE_RESOURCE_DIRECTORY , shown below, forms the root and
nodes of the tree.

WINNT.H

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  1. typedef struct _IMAGE_RESOURCE_DIRECTORY {  
  2.     ULONG   Characteristics;  
  3.     ULONG   TimeDateStamp;  
  4.     USHORT  MajorVersion;  
  5.     USHORT  MinorVersion;  
  6.     USHORT  NumberOfNamedEntries;  
  7.     USHORT  NumberOfIdEntries;  
  8. } IMAGE_RESOURCE_DIRECTORY, *PIMAGE_RESOURCE_DIRECTORY;  

Looking at the directory structure, you won’t find any pointer to the
next nodes. Instead, there are two
fields, NumberOfNamedEntries and NumberOfIdEntries , used to
indicate how many entries are attached to the directory. By attached ,
I mean the directory entries follow immediately after the directory in
the section data. The named entries appear first in ascending
alphabetical order, followed by the ID entries in ascending numerical
order.

A directory entry consists of two fields, as described in the
following IMAGE_RESOURCE_DIRECTORY_ENTRY structure:

WINNT.H

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  1. typedef struct _IMAGE_RESOURCE_DIRECTORY_ENTRY {  
  2.     ULONG   Name;  
  3.     ULONG   OffsetToData;  
  4. } IMAGE_RESOURCE_DIRECTORY_ENTRY, *PIMAGE_RESOURCE_DIRECTORY_ENTRY;  

The two fields are used for different things depending on the level of
the tree. The Name field is used to identify either a type of
resource, a resource name, or a resource’s language ID.
The OffsetToData field is always used to point to a sibling in the
tree, either a directory node or a leaf node.

Leaf nodes are the lowest node in the resource tree. They define the
size and location of the actual resource data. Each leaf node is
represented using the
following IMAGE_RESOURCE_DATA_ENTRY structure:

WINNT.H

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  1. typedef struct _IMAGE_RESOURCE_DATA_ENTRY {  
  2.     ULONG   OffsetToData;  
  3.     ULONG   Size;  
  4.     ULONG   CodePage;  
  5.     ULONG   Reserved;  
  6. } IMAGE_RESOURCE_DATA_ENTRY, *PIMAGE_RESOURCE_DATA_ENTRY;  

The two fields OffsetToData and Size indicate the location and size
of the actual resource data. Since this information is used primarily by
functions once the application has been loaded, it makes more sense to
make the OffsetToData field a relative virtual address. This is
precisely the case. Interestingly enough, all other offsets, such as
pointers from directory entries to other directories, are offsets
relative to the location of the root node.

To make all of this a little clearer, consider Figure 2.

home88一必发 4

Figure 2. A simple resource tree structure

Figure 2 depicts a very simple resource tree containing only two
resource objects, a menu, and a string table. Further, the menu and
string table have only one item each. Yet, you can see how complicated
the resource tree becomes—even with as few resources as this.

At the root of the tree, the first directory has one entry for each type
of resource the file contains, no matter how many of each type there
are. In Figure 2, there are two entries identified by the root, one for
the menu and one for the string table. If there had been one or more
dialog resources included in the file, the root node would have had one
more entry and, consequently, another branch for the dialog resources.

The basic resource types are identified in the file WINUSER.H and are
listed below:

WINUSER.H

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  1. /* 
  2.  * Predefined Resource Types 
  3.  */  
  4. #define RT_CURSOR           MAKEINTRESOURCE(1)  
  5. #define RT_BITMAP           MAKEINTRESOURCE(2)  
  6. #define RT_ICON             MAKEINTRESOURCE(3)  
  7. #define RT_MENU             MAKEINTRESOURCE(4)  
  8. #define RT_DIALOG           MAKEINTRESOURCE(5)  
  9. #define RT_STRING           MAKEINTRESOURCE(6)  
  10. #define RT_FONTDIR          MAKEINTRESOURCE(7)  
  11. #define RT_FONT             MAKEINTRESOURCE(8)  
  12. #define RT_ACCELERATOR      MAKEINTRESOURCE(9)  
  13. #define RT_RCDATA           MAKEINTRESOURCE(10)  
  14. #define RT_MESSAGETABLE     MAKEINTRESOURCE(11)  

At the top level of the tree, the MAKEINTRESOURCE values listed above
are placed in the Name field of each type entry, identifying the
different resources by type.

Each of the entries in the root directory points to a sibling node in
the second level of the tree. These nodes are directories, too, each
having their own entries. At this level, the directories are used to
identify the name of each resource within a given type. If you had
multiple menus defined in your application, there would be an entry for
each one here at the second level of the tree.

As you are probably already aware, resources can be identified by name
or by integer. They are distinguished in this level of the tree via
the Name field in the directory structure. If the most significant bit
of the Name field is set, the other 31 bits are used as an offset to
an IMAGE_RESOURCE_DIR_STRING_U structure.

WINNT.H

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  1. typedef struct _IMAGE_RESOURCE_DIR_STRING_U {  
  2.     USHORT  Length;  
  3.     WCHAR   NameString[ 1 ];  
  4. } IMAGE_RESOURCE_DIR_STRING_U, *PIMAGE_RESOURCE_DIR_STRING_U;  

This structure is simply a 2-byte Length field followed
by Length UNICODE characters.

On the other hand, if the most significant bit of the Name field is
clear, the lower 31 bits are used to represent the integer ID of the
resource. Figure 2 shows the menu resource as a named resource and the
string table as an ID resource.

If there were two menu resources, one identified by name and one by
resource, they would both have entries immediately after the menu
resource directory. The named resource entry would appear first,
followed by the integer-identified resource. The directory
fields NumberOfNamedEntries and NumberOfIdEntries would each contain
the value 1, indicating the presence of one entry.

Below level two, the resource tree does not branch out any further.
Level one branches into directories representing each type of resource,
and level two branches into directories representing each resource by
identifier. Level three maps a one-to-one correspondence between the
individually identified resources and their respective language IDs. To
indicate the language ID of a resource, the Name field of the
directory entry structure is used to indicate both the primary language
and sublanguage ID for the resource. The Win32 SDK for Windows NT lists
the default value resources. For the value 0x0409, 0x09 represents the
primary language as LANG_ENGLISH, and 0x04 is defined as
SUBLANG_ENGLISH_CAN for the sublanguage. The entire set of language
IDs is defined in the file WINNT.H, included as part of the Win32 SDK
for Windows NT.

Since the language ID node is the last directory node in the tree,
the OffsetToData field in the entry structure is an offset to a leaf
node—the IMAGE_RESOURCE_DATA_ENTRY structure mentioned earlier.

Referring back to Figure 2, you can see one data entry node for each
language directory entry. This node simply indicates the size of the
resource data and the relative virtual address where the resource data
is located.

One advantage to having so much structure to the resource data section,
.rsrc, is that you can glean a great deal of information from the
section without accessing the resources themselves. For example, you can
find out how many there are of each type of resource, what resources—if
any—use a particular language ID, whether a particular resource exists
or not, and the size of individual types of resources. To demonstrate
how to make use of this information, the following function shows how to
determine the different types of resources a file includes:

PEFILE.C

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  1. int     WINAPI GetListOfResourceTypes (  
  2.     LPVOID    lpFile,  
  3.     HANDLE    hHeap,  
  4.     char      **pszResTypes)  
  5. {  
  6.     PIMAGE_RESOURCE_DIRECTORY          prdRoot;  
  7.     PIMAGE_RESOURCE_DIRECTORY_ENTRY    prde;  
  8.     char                               *pMem;  
  9.     int                                nCnt, i;  
  10.   
  11.   
  12.     /* Get root directory of resource tree. */  
  13.     if ((prdRoot = PIMAGE_RESOURCE_DIRECTORY)ImageDirectoryOffset  
  14.            (lpFile, IMAGE_DIRECTORY_ENTRY_RESOURCE)) == NULL)  
  15.         return 0;  
  16.   
  17.     /* Allocate enough space from heap to cover all types. */  
  18.     nCnt = prdRoot->NumberOfIdEntries * (MAXRESOURCENAME + 1);  
  19.     *pszResTypes = (char *)HeapAlloc (hHeap,  
  20.                                       HEAP_ZERO_MEMORY,  
  21.                                       nCnt);  
  22.     if ((pMem = *pszResTypes) == NULL)  
  23.         return 0;  
  24.   
  25.     /*home88一必发, Set pointer to first resource type entry. */  
  26.     prde = (PIMAGE_RESOURCE_DIRECTORY_ENTRY)((DWORD)prdRoot +  
  27.                sizeof (IMAGE_RESOURCE_DIRECTORY));  
  28.   
  29.     /* Loop through all resource directory entry types. */  
  30.     for (i=0; i<prdRoot->NumberOfIdEntries; i++)  
  31.         {  
  32.         if (LoadString (hDll, prde->Name, pMem, MAXRESOURCENAME))  
  33.             pMem += strlen (pMem) + 1;  
  34.   
  35.         prde++;  
  36.         }  
  37.   
  38.     return nCnt;  
  39. }  

This function returns a list of resource type names in the string
identified by pszResTypes . Notice that, at the heart of this
function, LoadString is called using the Name field of each
resource type directory entry as the string ID. If you look in the
PEFILE.RC, you’ll see that I defined a series of resource type strings
whose IDs are defined the same as the type specifiers in the directory
entries. There is also a function in PEFILE.DLL that returns the total
number of resource objects in the .rsrc section. It would be rather easy
to expand on these functions or write new functions that extracted other
information from this section.

Export data section, .edata

The .edata section contains export data for an application or DLL. When
present, this section contains an export directory for getting to the
export information.

WINNT.H

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  1. typedef struct _IMAGE_EXPORT_DIRECTORY {  
  2.     ULONG   Characteristics;  
  3.     ULONG   TimeDateStamp;  
  4.     USHORT  MajorVersion;  
  5.     USHORT  MinorVersion;  
  6.     ULONG   Name;  
  7.     ULONG   Base;  
  8.     ULONG   NumberOfFunctions;  
  9.     ULONG   NumberOfNames;  
  10.     PULONG  *AddressOfFunctions;  
  11.     PULONG  *AddressOfNames;  
  12.     PUSHORT *AddressOfNameOrdinals;  
  13. } IMAGE_EXPORT_DIRECTORY, *PIMAGE_EXPORT_DIRECTORY;  

The Name field in the export directory identifies the name of the
executable module. NumberOfFunctions and NumberOfNames fields
indicate how many functions and function names are being exported from
the module.

The AddressOfFunctions field is an offset to a list of exported
function entry points. The AddressOfNames field is the address of an
offset to the beginning of a null-separated list of exported function
names. AddressOfNameOrdinals is an offset to a list of ordinal values
(each 2 bytes long) for the same exported functions.

The three AddressOf… fields are relative virtual addresses into the
address space of a process once the module has been loaded. Once the
module is loaded, the relative virtual address should be added to the
module base address to get the exact location in the address space of
the process. Before the file is loaded, however, the address can be
determined by subtracting the section header virtual address
(VirtualAddress ) from the given field address, adding the section
body offset (PointerToRawData ) to the result, and then using this
value as an offset into the image file. The following example
illustrates this technique:

PEFILE.C

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  1. int  WINAPI GetExportFunctionNames (  
  2.     LPVOID    lpFile,  
  3.     HANDLE    hHeap,  
  4.     char      **pszFunctions)  
  5. {  
  6.     IMAGE_SECTION_HEADER       sh;  
  7.     PIMAGE_EXPORT_DIRECTORY    ped;  
  8.     char                       *pNames, *pCnt;  
  9.     int                        i, nCnt;  
  10.   
  11.     /* Get section header and pointer to data directory  
  12.        for .edata section. */  
  13.     if ((ped = (PIMAGE_EXPORT_DIRECTORY)ImageDirectoryOffset  
  14.             (lpFile, IMAGE_DIRECTORY_ENTRY_EXPORT)) == NULL)  
  15.         return 0;  
  16.     GetSectionHdrByName (lpFile, &sh, “.edata”);  
  17.   
  18.     /* Determine the offset of the export function names. */  
  19.     pNames = (char *)(*(int *)((int)ped->AddressOfNames –  
  20.                                (int)sh.VirtualAddress   +  
  21.                                (int)sh.PointerToRawData +  
  22.                                (int)lpFile)    –  
  23.                       (int)sh.VirtualAddress   +  
  24.                       (int)sh.PointerToRawData +  
  25.                       (int)lpFile);  
  26.   
  27.     /* Figure out how much memory to allocate for all strings. */  
  28.     pCnt = pNames;  
  29.     for (i=0; i<(int)ped->NumberOfNames; i++)  
  30.         while (*pCnt++);  
  31.     nCnt = (int)(pCnt. pNames);  
  32.   
  33.     /* Allocate memory off heap for function names. */  
  34.     *pszFunctions = HeapAlloc (hHeap, HEAP_ZERO_MEMORY, nCnt);  
  35.   
  36.     /* Copy all strings to buffer. */  
  37.     CopyMemory ((LPVOID)*pszFunctions, (LPVOID)pNames, nCnt);  
  38.   
  39.     return nCnt;  
  40. }  

Notice that in this function the variable pNames is assigned by
determining first the address of the offset and then the actual offset
location. Both the address of the offset and the offset itself are
relative virtual addresses and must be translated before being used, as
the function demonstrates. You could write a similar function to
determine the ordinal values or entry points of the functions, but why
bother when I already did this for you?
The GetNumberOfExportedFunctions , GetExportFunctionEntryPoints ,
and GetExportFunctionOrdinals functions also exist in the
PEFILE.DLL.

Import data section, .idata

The .idata section is import data, including the import directory and
import address name table. Although an IMAGE_DIRECTORY_ENTRY_IMPORT
directory is defined, no corresponding import directory structure is
included in the file WINNT.H. Instead, there are several other
structures called IMAGE_IMPORT_BY_NAME, IMAGE_THUNK_DATA, and
IMAGE_IMPORT_DESCRIPTOR. Personally, I couldn’t make heads or tails of
how these structures are supposed to correlate to the .idata section, so
I spent several hours deciphering the .idata section body and came up
with a much simpler structure. I named this
structure IMAGE_IMPORT_MODULE_DIRECTORY .

PEFILE.H

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  1. typedef struct tagImportDirectory  
  2.     {  
  3.     DWORD    dwRVAFunctionNameList;  
  4.     DWORD    dwUseless1;  
  5.     DWORD    dwUseless2;  
  6.     DWORD    dwRVAModuleName;  
  7.     DWORD    dwRVAFunctionAddressList;  
  8.     }IMAGE_IMPORT_MODULE_DIRECTORY,  
  9.      * PIMAGE_IMPORT_MODULE_DIRECTORY;  

Unlike the data directories of other sections, this one repeats one
after another for each imported module in the file. Think of it as an
entry in a list of module data directories, rather than a data directory
to the entire section of data. Each entry is a directory to the import
information for a specific module.

One of the fields in the IMAGE_IMPORT_MODULE_DIRECTORY structure
is dwRVAModuleName , a relative virtual address pointing to the name
of the module. There are also two dwUseless parameters in the
structure that serve as padding to keep the structure aligned properly
within the section. The PE file format specification mentions something
about import flags, a time/date stamp, and major/minor versions, but
these two fields remained empty throughout my experimentation, so I
still consider them useless.

Based on the definition of this structure, you can retrieve the names of
modules and all functions in each module that are imported by an
executable file. The following function demonstrates how to retrieve all
the module names imported by a particular PE file:

PEFILE.C

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  1. int  WINAPI GetImportModuleNames (  
  2.     LPVOID    lpFile,  
  3.     HANDLE    hHeap,  
  4.     char      **pszModules)  
  5. {  
  6.     PIMAGE_IMPORT_MODULE_DIRECTORY  pid;  
  7.     IMAGE_SECTION_HEADER            idsh;  
  8.     BYTE                            *pData;  
  9.     int                             nCnt = 0, nSize = 0, i;  
  10.     char                            *pModule[1024];  
  11.     char                            *psz;  
  12.   
  13.     pid = (PIMAGE_IMPORT_MODULE_DIRECTORY)ImageDirectoryOffset   
  14.              (lpFile, IMAGE_DIRECTORY_ENTRY_IMPORT);  
  15.     pData = (BYTE *)pid;  
  16.   
  17.     /* Locate section header for “.idata” section. */  
  18.     if (!GetSectionHdrByName (lpFile, &idsh, “.idata”))  
  19.         return 0;  
  20.   
  21.     /* Extract all import modules. */  
  22.     while (pid->dwRVAModuleName)  
  23.         {  
  24.         /* Allocate buffer for absolute string offsets. */  
  25.         pModule[nCnt] = (char *)(pData +   
  26.                (pid->dwRVAModuleName-idsh.VirtualAddress));  
  27.         nSize += strlen (pModule[nCnt]) + 1;  
  28.   
  29.         /* Increment to the next import directory entry. */  
  30.         pid++;  
  31.         nCnt++;  
  32.         }  
  33.   
  34.     /* Copy all strings to one chunk of heap memory. */  
  35.     *pszModules = HeapAlloc (hHeap, HEAP_ZERO_MEMORY, nSize);  
  36.     psz = *pszModules;  
  37.     for (i=0; i<nCnt; i++)  
  38.         {  
  39.         strcpy (psz, pModule[i]);  
  40.         psz += strlen (psz) + 1;  
  41.         }  
  42.   
  43.     return nCnt;  
  44. }  

The function is pretty straightforward. However, one thing is worth
pointing out—notice the while loop. This loop is terminated
when pid->dwRVAModuleName is 0. Implied here is that at the end of
the list of IMAGE_IMPORT_MODULE_DIRECTORY structures is a null
structure that has a value of 0 for at least
the dwRVAModuleName field. This is the behavior I observed in my
experimentation with the file and later confirmed in the PE file format
specification.

The first field in the structure, dwRVAFunctionNameList , is a
relative virtual address to a list of relative virtual addresses that
each point to the function names within the file. As shown in the
following data, the module and function names of all imported modules
are listed in the .idata section data:

E6A7 0000 F6A7 0000  08A8 0000 1AA8 0000  ................
28A8 0000 3CA8 0000  4CA8 0000 0000 0000  (...<...L.......
0000 4765 744F 7065  6E46 696C 654E 616D  ..GetOpenFileNam
6541 0000 636F 6D64  6C67 3332 2E64 6C6C  eA..comdlg32.dll
0000 2500 4372 6561  7465 466F 6E74 496E  ..%.CreateFontIn
6469 7265 6374 4100  4744 4933 322E 646C  directA.GDI32.dl
6C00 A000 4765 7444  6576 6963 6543 6170  l...GetDeviceCap
7300 C600 4765 7453  746F 636B 4F62 6A65  s...GetStockObje
6374 0000 D500 4765  7454 6578 744D 6574  ct....GetTextMet
7269 6373 4100 1001  5365 6C65 6374 4F62  ricsA...SelectOb
6A65 6374 0000 1601  5365 7442 6B43 6F6C  ject....SetBkCol
6F72 0000 3501 5365  7454 6578 7443 6F6C  or..5.SetTextCol
6F72 0000 4501 5465  7874 4F75 7441 0000  or..E.TextOutA..

The above data is a portion taken from the .idata section of the
EXEVIEW.EXE sample application. This particular section represents the
beginning of the list of import module and function names. If you begin
examining the right section part of the data, you should recognize the
names of familiar Win32 API functions and the module names they are
found in. Reading from the top down, you get GetOpenFileNameA ,
followed by the module name COMDLG32.DLL. Shortly after that, you
get CreateFontIndirectA , followed by the module GDI32.DLL and then
the
functions GetDeviceCaps , GetStockObject , GetTextMetrics ,
and so forth.

This pattern repeats throughout the .idata section. The first module
name is COMDLG32.DLL and the second is GDI32.DLL. Notice that only one
function is imported from the first module, while many functions are
imported from the second module. In both cases, the function names and
the module name to which they belong are ordered such that a function
name appears first, followed by the module name and then by the rest of
the function names, if any.

The following function demonstrates how to retrieve the function names
for a specific module:

PEFILE.C

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  1. int  WINAPI GetImportFunctionNamesByModule (  
  2.     LPVOID    lpFile,  
  3.     HANDLE    hHeap,  
  4.     char      *pszModule,  
  5.     char      **pszFunctions)  
  6. {  
  7.     PIMAGE_IMPORT_MODULE_DIRECTORY  pid;  
  8.     IMAGE_SECTION_HEADER     idsh;  
  9.     DWORD                    dwBase;  
  10.     int                      nCnt = 0, nSize = 0;  
  11.     DWORD                    dwFunction;  
  12.     char                     *psz;  
  13.   
  14.   
  15.     /* Locate section header for “.idata” section. */  
  16.     if (!GetSectionHdrByName (lpFile, &idsh, “.idata”))  
  17.         return 0;  
  18.   
  19.     pid = (PIMAGE_IMPORT_MODULE_DIRECTORY)ImageDirectoryOffset   
  20.              (lpFile, IMAGE_DIRECTORY_ENTRY_IMPORT);  
  21.   
  22.     dwBase = ((DWORD)pid. idsh.VirtualAddress);  
  23.   
  24.     /* Find module’s pid. */  
  25.     while (pid->dwRVAModuleName &&  
  26.            strcmp (pszModule,   
  27.                   (char *)(pid->dwRVAModuleName+dwBase)))  
  28.         pid++;  
  29.   
  30.     /* Exit if the module is not found. */  
  31.     if (!pid->dwRVAModuleName)  
  32.         return 0;  
  33.   
  34.     /* Count number of function names and length of strings. */  
  35.     dwFunction = pid->dwRVAFunctionNameList;  
  36.     while (dwFunction                      &&  
  37.            *(DWORD *)(dwFunction + dwBase) &&  
  38.            *(char *)((*(DWORD *)(dwFunction + dwBase)) +  
  39.             dwBase+2))  
  40.         {  
  41.         nSize += strlen ((char *)((*(DWORD *)(dwFunction +  
  42.              dwBase)) + dwBase+2)) + 1;  
  43.         dwFunction += 4;  
  44.         nCnt++;  
  45.         }  
  46.   
  47.     /* Allocate memory off heap for function names. */  
  48.     *pszFunctions = HeapAlloc (hHeap, HEAP_ZERO_MEMORY, nSize);  
  49.     psz = *pszFunctions;  
  50.   
  51.     /* Copy function names to memory pointer. */  
  52.     dwFunction = pid->dwRVAFunctionNameList;  
  53.     while (dwFunction                      &&  
  54.            *(DWORD *)(dwFunction + dwBase) &&  
  55.            *((char *)((*(DWORD *)(dwFunction + dwBase)) +  
  56.             dwBase+2)))  
  57.         {  
  58.         strcpy (psz, (char *)((*(DWORD *)(dwFunction + dwBase)) +  
  59.                 dwBase+2));  
  60.         psz += strlen((char *)((*(DWORD *)(dwFunction + dwBase))+  
  61.                 dwBase+2)) + 1;  
  62.         dwFunction += 4;  
  63.         }  
  64.   
  65.     return nCnt;  
  66. }  

Like the GetImportModuleNames function, this function relies on the
end of each list of information to have a zeroed entry. In this case,
the list of function names ends with one that is zero.

The final field, dwRVAFunctionAddressList , is a relative virtual
address to a list of virtual addresses that will be placed in the
section data by the loader when the file is loaded. Before the file is
loaded, however, these virtual addresses are replaced by relative
virtual addresses that correspond exactly to the list of function names.
So before the file is loaded, there are two identical lists of relative
virtual addresses pointing to imported function names.

Debug information section, .debug

Debug information is initially placed in the .debug section. The PE file
format also supports separate debug files (normally identified with a
.DBG extension) as a means of collecting debug information in a central
location. The debug section contains the debug information, but the
debug directories live in the .rdata section mentioned earlier. Each of
those directories references debug information in the .debug section.
The debug directory structure is defined as
an IMAGE_DEBUG_DIRECTORY , as follows:

WINNT.H

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  1. typedef struct _IMAGE_DEBUG_DIRECTORY {  
  2.     ULONG   Characteristics;  
  3.     ULONG   TimeDateStamp;  
  4.     USHORT  MajorVersion;  
  5.     USHORT  MinorVersion;  
  6.     ULONG   Type;  
  7.     ULONG   SizeOfData;  
  8.     ULONG   AddressOfRawData;  
  9.     ULONG   PointerToRawData;  
  10. } IMAGE_DEBUG_DIRECTORY, *PIMAGE_DEBUG_DIRECTORY;  

The section is divided into separate portions of data representing
different types of debug information. For each one there is a debug
directory described above. The different types of debug information are
listed below:

WINNT.H

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  1. #define IMAGE_DEBUG_TYPE_UNKNOWN          0  
  2. #define IMAGE_DEBUG_TYPE_COFF             1  
  3. #define IMAGE_DEBUG_TYPE_CODEVIEW         2  
  4. #define IMAGE_DEBUG_TYPE_FPO              3  
  5. #define IMAGE_DEBUG_TYPE_MISC             4  

The Type field in each directory indicates which type of debug
information the directory represents. As you can see in the list above,
the PE file format supports many different types of debug information,
as well as some other informational fields. Of those,
the IMAGE_DEBUG_TYPE_MISC information is unique. This information
was added to represent miscellaneous information about the executable
image that could not be added to any of the more structured data
sections in the PE file format. This is the only location in the image
file where the image name is sure to appear. If an image exports
information, the export data section will also include the image name.

Each type of debug information has its own header structure that defines
its data. Each of these is listed in the file WINNT.H. One nice thing
about the IMAGE_DEBUG_DIRECTORY structure is that it includes two
fields that identify the debug information. The first of
these, AddressOfRawData , is the relative virtual address of the data
once the file is loaded. The other, PointerToRawData , is an actual
offset within the PE file, where the data is located. This makes it easy
to locate specific debug information.

As a last example, consider the following function, which extracts the
image name from the IMAGE_DEBUG_MISC structure:

PEFILE.C

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  1. int    WINAPI RetrieveModuleName (  
  2.     LPVOID    lpFile,  
  3.     HANDLE    hHeap,  
  4.     char      **pszModule)  
  5. {  
  6.   
  7.     PIMAGE_DEBUG_DIRECTORY    pdd;  
  8.     PIMAGE_DEBUG_MISC         pdm = NULL;  
  9.     int                       nCnt;  
  10.   
  11.     if (!(pdd = (PIMAGE_DEBUG_DIRECTORY)ImageDirectoryOffset  
  12.                (lpFile, IMAGE_DIRECTORY_ENTRY_DEBUG)))  
  13.         return 0;  
  14.   
  15.     while (pdd->SizeOfData)  
  16.         {  
  17.         if (pdd->Type == IMAGE_DEBUG_TYPE_MISC)  
  18.             {  
  19.             pdm = (PIMAGE_DEBUG_MISC)  
  20.                 ((DWORD)pdd->PointerToRawData + (DWORD)lpFile);  
  21.   
  22.             nCnt = lstrlen (pdm->Data)*(pdm->Unicode?2:1);  
  23.             *pszModule = (char *)HeapAlloc (hHeap,  
  24.                                             HEAP_ZERO_MEMORY,  
  25.                                             nCnt+1;  
  26.             CopyMemory (*pszModule, pdm->Data, nCnt);  
  27.   
  28.             break;  
  29.             }  
  30.   
  31.         pdd ++;  
  32.         }  
  33.   
  34.     if (pdm != NULL)  
  35.         return nCnt;  
  36.     else  
  37.         return 0;  
  38. }  

As you can see, the structure of the debug directory makes it relatively
easy to locate a specific type of debug information. Once
the IMAGE_DEBUG_MISC structure is located, extracting the image
name is as simple as invoking the CopyMemory function.

As mentioned above, debug information can be stripped into separate .DBG
files. The Windows NT SDK includes a utility called REBASE.EXE that
serves this purpose. For example, in the following statement an
executable image named TEST.EXE is being stripped of debug information:

rebase -b 40000 -x c:/samples/testdir test.exe

The debug information is placed in a new file called TEST.DBG and
located in the path specified, in this case c:/samples/testdir. The file
begins with a single IMAGE_SEPARATE_DEBUG_HEADER structure,
followed by a copy of the section headers that exist in the stripped
executable image. Then the .debug section data follows the section
headers. So, right after the section headers are the series
of IMAGE_DEBUG_DIRECTORY structures and their associated data. The
debug information itself retains the same structure as described above
for normal image file debug information.

Summary of the PE File Format

The PE file format for Windows NT introduces a completely new structure
to developers familiar with the Windows and MS-DOS environments. Yet
developers familiar with the UNIX environment will find that the PE file
format is similar to, if not based on, the COFF specification.

The entire format consists of an MS-DOS MZ header, followed by a
real-mode stub program, the PE file signature, the PE file header, the
PE optional header, all of the section headers, and finally, all of the
section bodies.

The optional header ends with an array of data directory entries that
are relative virtual addresses to data directories contained within
section bodies. Each data directory indicates how a specific section
body’s data is structured.

The PE file format has eleven predefined sections, as is common to
applications for Windows NT, but each application can define its own
unique sections for code and data.

The .debug predefined section also has the capability of being stripped
from the file into a separate debug file. If so, a special debug header
is used to parse the debug file, and a flag is specified in the PE file
header to indicate that the debug data has been stripped.

PEFILE.DLL Function Descriptions

PEFILE.DLL consists mainly of functions that either retrieve an offset
into a given PE file or copy a portion of the file data to a specific
structure. Each function has a single requirement—the first parameter is
a pointer to the beginning of the PE file. That is, the file must first
be memory-mapped into the address space of your process, and the base
location of the file mapping is the value lpFile that you pass as the
first parameter to every function.

The function names are meant to be self-explanatory, and each function
is listed with a brief comment describing its purpose. If, after reading
through the list of functions, you cannot determine what a function is
for, refer to the EXEVIEW.EXE sample application to find an example of
how the function is used. The following list of function prototypes can
also be found in PEFILE.H:

PEFE.H

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  1. /* Retrieve a pointer offset to the MS-DOS MZ header. */  
  2. BOOL WINAPI GetDosHeader (LPVOID, PIMAGE_DOS_HEADER);  
  3.   
  4. /* Determine the type of an .EXE file. */  
  5. DWORD WINAPI ImageFileType (LPVOID);  
  6.   
  7. /* Retrieve a pointer offset to the PE file header. */  
  8. BOOL WINAPI GetPEFileHeader (LPVOID, PIMAGE_FILE_HEADER);  
  9.   
  10. /* Retrieve a pointer offset to the PE optional header .*/  
  11. BOOL WINAPI GetPEOptionalHeader (LPVOID,  
  12.                                   PIMAGE_OPTIONAL_HEADER);  
  13.   
  14. /* Return the address of the module entry point. */  
  15. LPVOID WINAPI GetModuleEntryPoint (LPVOID);  
  16.   
  17. /* Return a count of the number of sections in the file. */  
  18. int  WINAPI NumOfSections (LPVOID);  
  19.   
  20. /* Return the desired base address of the executable when  
  21.    it is loaded into a process’s address space. */  
  22. LPVOID WINAPI GetImageBase (LPVOID);  
  23.   
  24. /* Determine the location within the file of a specific  
  25.    image data directory.  */  
  26. LPVOID WINAPI ImageDirectoryOffset (LPVOID, DWORD);  
  27.   
  28. /* Function retrieve names of all the sections in the file. */  
  29. int WINAPI GetSectionNames (LPVOID, HANDLE, char **);  
  30.   
  31. /* Copy the section header information for a specific section. */  
  32. BOOL WINAPI GetSectionHdrByName (LPVOID,  
  33.                                   PIMAGE_SECTION_HEADER, char *);  
  34.   
  35. /* Get null-separated list of import module names. */  
  36. int WINAPI GetImportModuleNames (LPVOID, HANDLE, char  **);  
  37.   
  38. /* Get null-separated list of import functions for a module. */  
  39. int WINAPI GetImportFunctionNamesByModule (LPVOID, HANDLE,  
  40.                                            char *, char  **);  
  41.   
  42. /* Get null-separated list of exported function names. */  
  43. int WINAPI GetExportFunctionNames (LPVOID, HANDLE, char **);  
  44.   
  45. /* Get number of exported functions. */  
  46. int WINAPI GetNumberOfExportedFunctions (LPVOID);  
  47.   
  48. /* Get list of exported function virtual address entry points. */  
  49. LPVOID WINAPI GetExportFunctionEntryPoints (LPVOID);  
  50.   
  51. /* Get list of exported function ordinal values. */  
  52. LPVOID WINAPI GetExportFunctionOrdinals (LPVOID);  
  53.   
  54. /* Determine total number of resource objects. */  
  55. int WINAPI GetNumberOfResources (LPVOID);  
  56.   
  57. /* Return list of all resource object types used in file. */  
  58. int WINAPI GetListOfResourceTypes (LPVOID, HANDLE, char **);  
  59.   
  60. /* Determine if debug information has been removed from file. */  
  61. BOOL WINAPI IsDebugInfoStripped (LPVOID);  
  62.   
  63. /* Get name of image file. */  
  64. int WINAPI RetrieveModuleName (LPVOID, HANDLE, char **);  
  65.   
  66. /* Function determines if the file is a valid debug file. */  
  67. BOOL WINAPI IsDebugFile (LPVOID);  
  68.   
  69. /* Function returns debug header from debug file. */  
  70. BOOL WINAPI GetSeparateDebugHeader(LPVOID,  
  71.                                    PIMAGE_SEPARATE_DEBUG_HEADER);  

In addition to the functions listed above, the macros mentioned earlier
in this article are also defined in the PEFILE.H file. The complete list
is as follows:

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  1. /* Offset to PE file signature                              */  
  2. #define NTSIGNATURE(a) ((LPVOID)((BYTE *)a                +  /  
  3.                         ((PIMAGE_DOS_HEADER)a)->e_lfanew))  
  4.   
  5. /* MS-OS header identifies the NT PEFile signature dword; 
  6.    the PEFILE header exists just after that dword.           */  
  7. #define PEFHDROFFSET(a) ((LPVOID)((BYTE *)a               +  /  
  8.                          ((PIMAGE_DOS_HEADER)a)->e_lfanew +  /  
  9.                              SIZE_OF_NT_SIGNATURE))  
  10.   
  11. /* PE optional header is immediately after PEFile header.    */  
  12. #define OPTHDROFFSET(a) ((LPVOID)((BYTE *)a               +  /  
  13.                          ((PIMAGE_DOS_HEADER)a)->e_lfanew +  /  
  14.                            SIZE_OF_NT_SIGNATURE           +  /  
  15.                            sizeof (IMAGE_FILE_HEADER)))  
  16.   
  17. /* Section headers are immediately after PE optional header. */  
  18. #define SECHDROFFSET(a) ((LPVOID)((BYTE *)a               +  /  
  19.                          ((PIMAGE_DOS_HEADER)a)->e_lfanew +  /  
  20.                            SIZE_OF_NT_SIGNATURE           +  /  
  21.                            sizeof (IMAGE_FILE_HEADER)     +  /  
  22.                            sizeof (IMAGE_OPTIONAL_HEADER)))  

To use PEFILE.DLL, simply include the header file PEFILE.H and link the
DLL to your application. All of the functions are mutually exclusive
functions, but some were written as much to support others as for the
information they provide. For example, the
function GetSectionNames is useful for getting the exact names of
all sections. Yet to be able to retrieve the section header for a unique
section name (one defined by the application developer during compile),
you would first have to get the list of names and then call the
function GetSectionHeaderByName with the exact name of the section.
Enjoy!

 

 


 

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