kc3-lang/libevent

2016-01-31T00:57:16

evutil_parse_sockaddr_port(): fix buffer overflow @asn-the-goblin-slayer: "Length between '[' and ']' is cast to signed 32 bit integer on line 1815. Is the length is more than 2<<31 (INT_MAX), len will hold a negative value. Consequently, it will pass the check at line 1816. Segfault happens at line 1819. Generate a resolv.conf with generate-resolv.conf, then compile and run poc.c. See entry-functions.txt for functions in tor that might be vulnerable. Please credit 'Guido Vranken' for this discovery through the Tor bug bounty program." Reproducer for gdb (https://gist.github.com/azat/be2b0d5e9417ba0dfe2c): start p (1ULL<<31)+1ULL # $1 = 2147483649 p malloc(sizeof(struct sockaddr)) # $2 = (void *) 0x646010 p malloc(sizeof(int)) # $3 = (void *) 0x646030 p malloc($1) # $4 = (void *) 0x7fff76a2a010 p memset($4, 1, $1) # $5 = 1990369296 p (char *)$4 # $6 = 0x7fff76a2a010 '\001' <repeats 200 times>... set $6[0]='[' set $6[$1]=']' p evutil_parse_sockaddr_port($4, $2, $3) # $7 = -1 Before: $ gdb bin/http-connect < gdb (gdb) $1 = 2147483649 (gdb) (gdb) $2 = (void *) 0x646010 (gdb) (gdb) $3 = (void *) 0x646030 (gdb) (gdb) $4 = (void *) 0x7fff76a2a010 (gdb) (gdb) $5 = 1990369296 (gdb) (gdb) $6 = 0x7fff76a2a010 '\001' <repeats 200 times>... (gdb) (gdb) (gdb) (gdb) Program received signal SIGSEGV, Segmentation fault. __memcpy_sse2_unaligned () at memcpy-sse2-unaligned.S:36 After: $ gdb bin/http-connect < gdb (gdb) $1 = 2147483649 (gdb) (gdb) $2 = (void *) 0x646010 (gdb) (gdb) $3 = (void *) 0x646030 (gdb) (gdb) $4 = (void *) 0x7fff76a2a010 (gdb) (gdb) $5 = 1990369296 (gdb) (gdb) $6 = 0x7fff76a2a010 '\001' <repeats 200 times>... (gdb) (gdb) (gdb) (gdb) $7 = -1 (gdb) (gdb) quit Fixes: #318