From d72a7e4da1001b29a661a4b1a52cb5c4d708bab0 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Mon, 17 Jun 2019 22:14:09 +0900 Subject: [PATCH] Fix buffer overflow when processing SCRAM final message in libpq When a client connects to a rogue server sending specifically-crafted messages, this can suffice to execute arbitrary code as the operating system account used by the client. While on it, fix one error handling when decoding an incorrect salt included in the first message received from server. Author: Michael Paquier Reviewed-by: Jonathan Katz, Heikki Linnakangas Security: CVE-2019-10164 Backpatch-through: 10 --- src/interfaces/libpq/fe-auth-scram.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c index 7fa7f34c80b..4cdf9ba93bc 100644 --- a/src/interfaces/libpq/fe-auth-scram.c +++ b/src/interfaces/libpq/fe-auth-scram.c @@ -462,6 +462,12 @@ read_server_first_message(fe_scram_state *state, char *input, state->saltlen = pg_b64_decode(encoded_salt, strlen(encoded_salt), state->salt); + if (state->saltlen < 0) + { + printfPQExpBuffer(errormessage, + libpq_gettext("malformed SCRAM message (invalid salt)\n")); + return false; + } iterations_str = read_attr_value(&input, 'i', errormessage); if (iterations_str == NULL) @@ -492,6 +498,7 @@ read_server_final_message(fe_scram_state *state, char *input, PQExpBuffer errormessage) { char *encoded_server_signature; + char *decoded_server_signature; int server_signature_len; state->server_final_message = strdup(input); @@ -525,15 +532,27 @@ read_server_final_message(fe_scram_state *state, char *input, printfPQExpBuffer(errormessage, libpq_gettext("malformed SCRAM message (garbage at end of server-final-message)\n")); + server_signature_len = pg_b64_dec_len(strlen(encoded_server_signature)); + decoded_server_signature = malloc(server_signature_len); + if (!decoded_server_signature) + { + printfPQExpBuffer(errormessage, + libpq_gettext("out of memory\n")); + return false; + } + server_signature_len = pg_b64_decode(encoded_server_signature, strlen(encoded_server_signature), - state->ServerSignature); + decoded_server_signature); if (server_signature_len != SCRAM_KEY_LEN) { + free(decoded_server_signature); printfPQExpBuffer(errormessage, libpq_gettext("malformed SCRAM message (invalid server signature)\n")); return false; } + memcpy(state->ServerSignature, decoded_server_signature, SCRAM_KEY_LEN); + free(decoded_server_signature); return true; }