Yama LSM

In this post, the basics of coding Intel Pin tools will be presented, but before we discuss this, you should be aware that a Linux Security Module exists that prevents binary instrumentation by default. Yama is a Linux Security Module that collects a number of system-wide DAC security protections that are not handled by the core kernel itself. Yama is controlled using sysctl. A description of some of the possible values for /proc/sys/kernel/yama/ptrace_scope is provided below:

• 0 => Classic ptrace: a process can PTRACE_ATTACH to any other process running under the same uid, as long as it is dumpable.
• 1 => Restricted ptrace: a process can only PTRACE_ATTACH only its descendants although an inferior can call prctl(PR_SET_PTRACER, debugger, …) to allow the debugger to call PTRACE_ATTACH.
• 2 => Admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace with PTRACE_ATTACH
• 3 => No attach: no processes may use ptrace with PTRACE_ATTACH nor via PTRACE_TRACEME.

For detailed information, visit the Linux kernel documentation about Yama.

Continuing with the Pin topic, it should be noted that if a Pin tool is executed without setting /proc/sys/kernel/yama/ptrace_scope to 0, the following message will appear:

$ ../pin/pin -t obj-intel64/check_pc_sections.so -- /bin/ls
E:Attach to pid 9495 failed.
E:  The Operating System configuration prevents Pin from using the default (parent) injection mode.
E:  To resolve this, either execute the following (as root):
E:  $ echo 0 > /proc/sys/kernel/yama/ptrace_scope
E:  Or use the "-injection child" option.
E:  For more information, regarding child injection, see Injection section in the Pin User Manual.
E:
Terminado (killed)

To allow debugging of inferior processes the value of /proc/sys/kernel/yama/ptrace_scope needs to be changed using sysctl:

# sysctl kernel.yama.ptrace_scope=0
kernel.yama.ptrace_scope = 0

Pin tools

The Pin tools are the tools created using Pin and used to perform program analysis on user space. Pin tools that perform the binary instrumentation have two key components:

1. The instrumentation callback routine: a mechanism that decides if and where to inject calls to analysis functions; and
2. The analysis function: code to execute at insertion points.

Note that the Pin tools are able to control a program starting with the very first instruction, meaning that it is possible even to inspect the linker’s code of a binary loading shared libraries. This could be utilised to perform run-time bug hunting in the operating system linker. Also, when programming Pin tools, it should be kept in mind that as the Pin documentation specifies, it is more important to tune the analysis code than the instrumentation code. This is because the instrumentation is executed once, but analysis code is called many times.

Executable Images and Sections

Pin provides access to the binary’s images and image sections using linked lists. Those lists can be traversed using the API calls APP_ImgHead(), App_ImgTail(), IMG_Valid(IMG x), IMG_Next(IMG x) and IMG_Previous(IMG x); additionally, a number a API functions exist for accessing image properties such as name, size, type, start address, etc. A detailed view of the image API can be examined in the image API documentation.

The image sections have the equivalent API functions to traverse the linked list: IMG_SecHead(IMG x),IMG_SecTail(IMG x), SEC_Valid(sec x), SEC_Prev(sec x), SEC_Next(sec x), SEC_Address (SEC sec), SEC_Valid (SEC x), etc. The complete list can be found in the section API documentation.

To illustrate the usage of the image and section API an example is provided:

#include "pin.H"
#include <iostream>
#include <fstream>
#include <string.h>

// =====================================================================
// Usage
// =====================================================================

INT32 Usage()
{
    cerr << "[*] This Pin tool prints the images and section names of a binary when loading" << endl;
    return -1;
}

// =====================================================================
// Analysis routines
// =====================================================================

// Prints image and section name, type and address
VOID loadImageSec(IMG img, VOID *v)
{
    UINT64 sec_cont = 0;
    string img_type;
    string sec_type;

    switch (IMG_Type(img)){
        case IMG_TYPE_STATIC:
            img_type = "static";
            break;
        case IMG_TYPE_SHARED:
            img_type = "shared";
            break;
        case IMG_TYPE_SHAREDLIB:
            img_type = "shared library";
            break;
        case IMG_TYPE_RELOCATABLE:
            img_type = "relocatable";
            break;
        default:
            img_type = "unknown";
    }

    cout << "[*] Loading image " << IMG_Name(img).c_str();
    cout << " @ " << StringFromAddrint(IMG_StartAddress(img));
    cout << " type " << img_type << endl;

    for (SEC sec=IMG_SecHead(img); SEC_Valid(sec); sec=SEC_Next(sec)) {
        if (strcmp(SEC_Name(sec).c_str(),"")) {

            switch (SEC_Type(sec)){
                case SEC_TYPE_REGREL:
                    sec_type = "relocations";
                    break;
                case SEC_TYPE_DYNREL:
                    sec_type = "dynamic relocations";
                    break;
                case SEC_TYPE_EXEC:
                    sec_type = "code";
                    break;
                case SEC_TYPE_DATA:
                    sec_type = "initialized data";
                    break;
                case SEC_TYPE_BSS:
                    sec_type = "unitialized data";
                    break;
                case SEC_TYPE_LOOS:
                    sec_type = "operating system specific";
                    break;
                case SEC_TYPE_USER:
                    sec_type = "user application specific";
                    break;
                default:
                    sec_type = "unknown";
            }

            cout << "\t => Loading section " << SEC_Name(sec).c_str();
            cout << " @ " << StringFromAddrint(SEC_Address(sec));
            cout << " type " << sec_type << endl;

            sec_cont++;
        }
    }

    cout << "[*] Done loading " << IMG_Name(img).c_str() << ": " << sec_cont << " sections" << endl;

}

// =====================================================================
// Main
// =====================================================================

int main(int argc, char *argv[])
{

    if(PIN_Init(argc,argv)) {
        return Usage();
    }

    cout << "[*] Executing Pin tool" << endl;
    cout << "[*] Adding instrumentation functions" << endl;
    IMG_AddInstrumentFunction(loadImageSec, 0);

    cout << "[*] Executing target program" << endl;
    PIN_StartProgram();

    return 0;
}
// EOF

To compile the Pin tool, save the code as load_bin_img_sec.cpp and execute the following cmd line on the custom development directory as explained in the previous article:

~/mytools $ ./build.sh
[*] Building load_bin_img_sec.cpp
g++ -DBIGARRAY_MULTIPLIER=1 -DUSING_XED -Wall -Werror -Wno-unknown-pragmas -fno-stack-protector -DTARGET_IA32E -DHOST_IA32E -fPIC -DTARGET_LINUX  -I../pin/source/include/pin -I../pin/source/include/pin/gen -I../pin/extras/components/include -I../pin/extras/xed2-intel64/include -I../pin/source/tools/InstLib -O3 -fomit-frame-pointer -fno-strict-aliasing   -c -o obj-intel64/load_bin_img_sec.o load_bin_img_sec.cpp
g++ -shared -Wl,--hash-style=sysv -Wl,-Bsymbolic -Wl,--version-script=../pin/source/include/pin/pintool.ver    -o obj-intel64/load_bin_img_sec.so obj-intel64/load_bin_img_sec.o  -L../pin/intel64/lib -L../pin/intel64/lib-ext -L../pin/intel64/runtime/glibc -L../pin/extras/xed2-intel64/lib -lpin -lxed -ldwarf -lelf -ldl
[*] Exec ../pin/pin -t obj-intel64/load_bin_img_sec.so -- <program>

The binary /bin/ls is taken as example target binary for the execution of compiled Pin tool:

~/mytools $ ../pin/pin -t obj-intel64/load_bin_img_sec.so -- /bin/ls /tmp/
[*] Executing PIN tool
[*] Adding instrumentation functions
[*] Executing target program
[*] Loading image /usr/bin/ls @ 0x00007f55b8798000 type shared
	 => Loading section .interp @ 0x0000000000400238 type initialized data
	 => Loading section .note.ABI-tag @ 0x0000000000400254 type initialized data
	 => Loading section .note.gnu.build-id @ 0x0000000000400274 type initialized data
	 => Loading section .dynsym @ 0x0000000000400350 type unknown
	 => Loading section .dynstr @ 0x0000000000400f50 type unknown
	 => Loading section .rela.dyn @ 0x0000000000401670 type relocations
	 => Loading section .rela.plt @ 0x0000000000401718 type relocations
	 => Loading section .init @ 0x0000000000402180 type code
	 => Loading section .plt @ 0x00000000004021a0 type code
	 => Loading section .text @ 0x00000000004028a0 type code
	 => Loading section .fini @ 0x0000000000411d4c type code
	 => Loading section .rodata @ 0x0000000000411d60 type initialized data
	 => Loading section .eh_frame_hdr @ 0x0000000000416e7c type initialized data
	 => Loading section .eh_frame @ 0x0000000000417588 type initialized data
	 => Loading section .init_array @ 0x0000000000619df0 type initialized data
	 => Loading section .fini_array @ 0x0000000000619df8 type initialized data
	 => Loading section .jcr @ 0x0000000000619e00 type initialized data
	 => Loading section .dynamic @ 0x0000000000619e08 type unknown
	 => Loading section .got @ 0x0000000000619ff8 type unknown
	 => Loading section .got.plt @ 0x000000000061a000 type initialized data
	 => Loading section .data @ 0x000000000061a3a0 type initialized data
	 => Loading section .bss @ 0x000000000061a600 type unitialized data
	 => Loading section .comment @ 0x0000000000000000 type unknown
	 => Loading section .shstrtab @ 0x0000000000000000 type unknown
[*] Done loading /usr/bin/ls: 24 sections
[*] Loading image /lib64/ld-linux-x86-64.so.2 @ 0x00007f55b8788000 type shared library
	 => Loading section .note.gnu.build-id @ 0x00007f55cb9201c8 type initialized data
	 => Loading section .hash @ 0x00007f55cb9201f0 type unknown
	 => Loading section .dynsym @ 0x00007f55cb920470 type unknown
	 => Loading section .dynstr @ 0x00007f55cb920710 type unknown
	 => Loading section .rela.dyn @ 0x00007f55cb920988 type relocations
	 => Loading section .rela.plt @ 0x00007f55cb920ac0 type relocations
	 => Loading section .plt @ 0x00007f55cb920b50 type code
	 => Loading section .text @ 0x00007f55cb920bc0 type code
	 => Loading section .rodata @ 0x00007f55cb939100 type initialized data
	 => Loading section .eh_frame_hdr @ 0x00007f55cb93d300 type initialized data
	 => Loading section .eh_frame @ 0x00007f55cb93d950 type initialized data
	 => Loading section .data.rel.ro @ 0x00007f55cbb40ba0 type initialized data
	 => Loading section .dynamic @ 0x00007f55cbb40e10 type unknown
	 => Loading section .got @ 0x00007f55cbb40fa0 type unknown
	 => Loading section .data @ 0x00007f55cbb41000 type initialized data
	 => Loading section .bss @ 0x00007f55cbb41fa0 type unitialized data
	 => Loading section .comment @ 0x0000000000000000 type unknown
	 => Loading section .shstrtab @ 0x0000000000000000 type unknown
	 => Loading section .symtab @ 0x0000000000000000 type unknown
	 => Loading section .strtab @ 0x0000000000000000 type unknown
[*] Done loading /lib64/ld-linux-x86-64.so.2: 20 sections
[*] Loading image /usr/lib/libcap.so.2 @ 0x00007f55b7c50000 type shared library
	 => Loading section .note.gnu.build-id @ 0x00007f55b84a8190 type initialized data
	 => Loading section .dynsym @ 0x00007f55b84a82b0 type unknown
	 => Loading section .dynstr @ 0x00007f55b84a8898 type unknown
	 => Loading section .rela.dyn @ 0x00007f55b84a8c30 type relocations
	 => Loading section .rela.plt @ 0x00007f55b84a9080 type relocations
	 => Loading section .init @ 0x00007f55b84a9350 type code
	 => Loading section .plt @ 0x00007f55b84a9370 type code
	 => Loading section .text @ 0x00007f55b84a9560 type code
	 => Loading section .fini @ 0x00007f55b84aac54 type code
	 => Loading section .rodata @ 0x00007f55b84aac60 type initialized data
	 => Loading section .eh_frame_hdr @ 0x00007f55b84aaf48 type initialized data
	 => Loading section .eh_frame @ 0x00007f55b84ab060 type initialized data
	 => Loading section .init_array @ 0x00007f55b86ab648 type initialized data
	 => Loading section .fini_array @ 0x00007f55b86ab650 type initialized data
	 => Loading section .jcr @ 0x00007f55b86ab658 type initialized data
	 => Loading section .dynamic @ 0x00007f55b86ab660 type unknown
	 => Loading section .got @ 0x00007f55b86ab840 type unknown
	 => Loading section .got.plt @ 0x00007f55b86ab870 type initialized data
	 => Loading section .data @ 0x00007f55b86ab980 type initialized data
	 => Loading section .bss @ 0x00007f55b86abac8 type unitialized data
	 => Loading section .comment @ 0x0000000000000000 type unknown
	 => Loading section .shstrtab @ 0x0000000000000000 type unknown
[*] Done loading /usr/lib/libcap.so.2: 22 sections
[*] Loading image /usr/lib/libacl.so.1 @ 0x00007f55b7c48000 type shared library
	 => Loading section .note.gnu.build-id @ 0x00007f55b82881c8 type initialized data
	 => Loading section .dynsym @ 0x00007f55b82884f8 type unknown
	 => Loading section .dynstr @ 0x00007f55b8288ed0 type unknown
	 => Loading section .rela.dyn @ 0x00007f55b8289580 type relocations
	 => Loading section .rela.plt @ 0x00007f55b8289700 type relocations
	 => Loading section .init @ 0x00007f55b8289cb8 type code
	 => Loading section .plt @ 0x00007f55b8289ce0 type code
	 => Loading section .text @ 0x00007f55b828a0c0 type code
	 => Loading section .fini @ 0x00007f55b828dea4 type code
	 => Loading section .rodata @ 0x00007f55b828deb0 type initialized data
	 => Loading section .eh_frame_hdr @ 0x00007f55b828e154 type initialized data
	 => Loading section .eh_frame @ 0x00007f55b828e380 type initialized data
	 => Loading section .init_array @ 0x00007f55b848fd98 type initialized data
	 => Loading section .fini_array @ 0x00007f55b848fda0 type initialized data
	 => Loading section .jcr @ 0x00007f55b848fda8 type initialized data
	 => Loading section .dynamic @ 0x00007f55b848fdb0 type unknown
	 => Loading section .got @ 0x00007f55b848ffb0 type unknown
	 => Loading section .got.plt @ 0x00007f55b8490000 type initialized data
	 => Loading section .data @ 0x00007f55b8490200 type initialized data
	 => Loading section .bss @ 0x00007f55b8490270 type unitialized data
	 => Loading section .comment @ 0x0000000000000000 type unknown
	 => Loading section .shstrtab @ 0x0000000000000000 type unknown
[*] Done loading /usr/lib/libacl.so.1: 22 sections
[*] Loading image /usr/lib/libc.so.6 @ 0x00007f55b7a68000 type shared library
	 => Loading section .note.gnu.build-id @ 0x00007f55b7ee0270 type initialized data
	 => Loading section .note.ABI-tag @ 0x00007f55b7ee0294 type initialized data
	 => Loading section .dynsym @ 0x00007f55b7ee3d28 type unknown
	 => Loading section .dynstr @ 0x00007f55b7ef0d78 type unknown
	 => Loading section .rela.dyn @ 0x00007f55b7ef7b10 type relocations
	 => Loading section .rela.plt @ 0x00007f55b7eff298 type relocations
	 => Loading section .plt @ 0x00007f55b7eff3c0 type code
	 => Loading section .text @ 0x00007f55b7eff490 type code
	 => Loading section __libc_freeres_fn @ 0x00007f55b8028bc0 type code
	 => Loading section __libc_thread_freeres_fn @ 0x00007f55b80299b0 type code
	 => Loading section .rodata @ 0x00007f55b8029ba0 type initialized data
	 => Loading section .interp @ 0x00007f55b804b790 type initialized data
	 => Loading section .eh_frame_hdr @ 0x00007f55b804b7b0 type initialized data
	 => Loading section .eh_frame @ 0x00007f55b80521e0 type initialized data
	 => Loading section .gcc_except_table @ 0x00007f55b807a954 type initialized data
	 => Loading section .hash @ 0x00007f55b807ad18 type unknown
	 => Loading section .tdata @ 0x00007f55b827e718 type initialized data
	 => Loading section .tbss @ 0x00007f55b827e728 type unitialized data
	 => Loading section .init_array @ 0x00007f55b827e728 type initialized data
	 => Loading section __libc_subfreeres @ 0x00007f55b827e730 type initialized data
	 => Loading section __libc_atexit @ 0x00007f55b827e820 type initialized data
	 => Loading section __libc_thread_subfreeres @ 0x00007f55b827e828 type initialized data
	 => Loading section .data.rel.ro @ 0x00007f55b827e860 type initialized data
	 => Loading section .dynamic @ 0x00007f55b8281b80 type unknown
	 => Loading section .got @ 0x00007f55b8281d70 type unknown
	 => Loading section .got.plt @ 0x00007f55b8282000 type initialized data
	 => Loading section .data @ 0x00007f55b8282080 type initialized data
	 => Loading section .bss @ 0x00007f55b8283740 type unitialized data
	 => Loading section .comment @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.sigstack @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.sigreturn @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.siggetmask @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.tmpnam @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.tmpnam_r @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.tempnam @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.sys_errlist @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.sys_nerr @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.gets @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.getpw @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.re_max_failures @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.lchmod @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.getwd @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.sstk @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.revoke @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.mktemp @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.gtty @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.stty @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.chflags @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.fchflags @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.bdflush @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.__gets_chk @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.inet6_option_space @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.inet6_option_init @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.inet6_option_append @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.inet6_option_alloc @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.inet6_option_next @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.inet6_option_find @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.getmsg @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.putmsg @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.fattach @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.fdetach @ 0x0000000000000000 type unknown
	 => Loading section .gnu.warning.setlogin @ 0x0000000000000000 type unknown
	 => Loading section .shstrtab @ 0x0000000000000000 type unknown
	 => Loading section .symtab @ 0x0000000000000000 type unknown
	 => Loading section .strtab @ 0x0000000000000000 type unknown
[*] Done loading /usr/lib/libc.so.6: 65 sections
[*] Loading image /usr/lib/libattr.so.1 @ 0x00007f55b7c50000 type shared library
	 => Loading section .note.gnu.build-id @ 0x00007f55b7cd81c8 type initialized data
	 => Loading section .dynsym @ 0x00007f55b7cd8378 type unknown
	 => Loading section .dynstr @ 0x00007f55b7cd8930 type unknown
	 => Loading section .rela.dyn @ 0x00007f55b7cd8ce8 type relocations
	 => Loading section .rela.plt @ 0x00007f55b7cd8dc0 type relocations
	 => Loading section .init @ 0x00007f55b7cd9198 type code
	 => Loading section .plt @ 0x00007f55b7cd91c0 type code
	 => Loading section .text @ 0x00007f55b7cd9460 type code
	 => Loading section .fini @ 0x00007f55b7cdb4ac type code
	 => Loading section .rodata @ 0x00007f55b7cdb4b5 type initialized data
	 => Loading section .eh_frame_hdr @ 0x00007f55b7cdb56c type initialized data
	 => Loading section .eh_frame @ 0x00007f55b7cdb668 type initialized data
	 => Loading section .init_array @ 0x00007f55b7edbdc8 type initialized data
	 => Loading section .fini_array @ 0x00007f55b7edbdd0 type initialized data
	 => Loading section .jcr @ 0x00007f55b7edbdd8 type initialized data
	 => Loading section .dynamic @ 0x00007f55b7edbde0 type unknown
	 => Loading section .got @ 0x00007f55b7edbfd0 type unknown
	 => Loading section .got.plt @ 0x00007f55b7edc000 type initialized data
	 => Loading section .data @ 0x00007f55b7edc160 type initialized data
	 => Loading section .bss @ 0x00007f55b7edc168 type unitialized data
	 => Loading section .comment @ 0x0000000000000000 type unknown
	 => Loading section .shstrtab @ 0x0000000000000000 type unknown
[*] Done loading /usr/lib/libattr.so.1: 22 sections
PKGBUILD      plugtmp  test-kernel-security.py  yaourt-tmp-user
~/mytools $

As you can see, Intel Pin tool provides a rich API to inspect the different parts of a binary, including sections, images, functions, registers, etc, which could help security researchers to detect an anomalies such us:

• Whether the instruction pointer points to a memory address outside the code segment?
• Are parts of the memory getting overwritten by user input?
• Whether there are too many RETs getting executed within a small part of the code

The post Using Intel Pin tools for binary instrumentation appeared first on Portcullis Labs.