From cca6198c777dba463aeb4a8fba6a953cde9576a8 Mon Sep 17 00:00:00 2001 From: Nick Mathewson Date: Tue, 10 Jun 2014 11:11:47 -0400 Subject: Avoid illegal read off end of an array in prune_v2_cipher_list This function is supposed to construct a list of all the ciphers in the "v2 link protocol cipher list" that are supported by Tor's openssl. It does this by invoking ssl23_get_cipher_by_char on each two-byte ciphersuite ID to see which ones give a match. But when ssl23_get_cipher_by_char cannot find a match for a two-byte SSL3/TLS ciphersuite ID, it checks to see whether it has a match for a three-byte SSL2 ciphersuite ID. This was causing a read off the end of the 'cipherid' array. This was probably harmless in practice, but we shouldn't be having any uninitialized reads. (Using ssl23_get_cipher_by_char in this way is a kludge, but then again the entire existence of the v2 link protocol is kind of a kludge. Once Tor 0.2.2 clients are all gone, we can drop this code entirely.) Found by starlight. Fix on 0.2.4.8-alpha. Fixes bug 12227. --- src/common/tortls.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'src') diff --git a/src/common/tortls.c b/src/common/tortls.c index 8f3f6a713..c13b12fd4 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -1489,10 +1489,13 @@ prune_v2_cipher_list(void) inp = outp = v2_cipher_list; while (*inp) { - unsigned char cipherid[2]; + unsigned char cipherid[3]; const SSL_CIPHER *cipher; /* Is there no better way to do this? */ set_uint16(cipherid, htons(*inp)); + cipherid[2] = 0; /* If ssl23_get_cipher_by_char finds no cipher starting + * with a two-byte 'cipherid', it may look for a v2 + * cipher with the appropriate 3 bytes. */ cipher = m->get_cipher_by_char(cipherid); if (cipher) { tor_assert((cipher->id & 0xffff) == *inp); -- cgit v1.2.3