commit 2b27ce52d2b96a91410fbf8e9c6f2ce7cf036961 Author: John Brooks john.brooks@dereferenced.net Date: Sat Apr 25 22:52:35 2015 -0600

Fix out-of-bounds read in INTRODUCE2 client auth

The length of auth_data from an INTRODUCE2 cell is checked when the auth_type is recognized (1 or 2), but not for any other non-zero auth_type. Later, auth_data is assumed to have at least REND_DESC_COOKIE_LEN bytes, leading to a client-triggered out of bounds read.

Fixed by checking auth_len before comparing the descriptor cookie against known clients.

Fixes #15823; bugfix on 0.2.1.6-alpha. --- changes/bug15823 | 4 ++++ src/or/rendservice.c | 18 ++++++++++++++---- 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/changes/bug15823 b/changes/bug15823 new file mode 100644 index 0000000..987de5d --- /dev/null +++ b/changes/bug15823 @@ -0,0 +1,4 @@ + o Minor bugfixes (hidden service): + - Fix an out-of-bounds read when parsing invalid INTRODUCE2 cells + on a client authorized hidden service. Fixes bug 15823; bugfix + on 0.2.1.6-alpha. diff --git a/src/or/rendservice.c b/src/or/rendservice.c index 4a8d6c5..d958de9 100644 --- a/src/or/rendservice.c +++ b/src/or/rendservice.c @@ -969,11 +969,13 @@ rend_service_requires_uptime(rend_service_t *service) return 0; }

-/** Check client authorization of a given <b>descriptor_cookie</b> for - * <b>service</b>. Return 1 for success and 0 for failure. */ +/** Check client authorization of a given <b>descriptor_cookie</b> of + * length <b>cookie_len</b> for <b>service</b>. Return 1 for success + * and 0 for failure. */ static int rend_check_authorization(rend_service_t *service, - const char *descriptor_cookie) + const char *descriptor_cookie, + size_t cookie_len) { rend_authorized_client_t *auth_client = NULL; tor_assert(service); @@ -984,6 +986,13 @@ rend_check_authorization(rend_service_t *service, return 0; }

+ if (cookie_len != REND_DESC_COOKIE_LEN) { + log_info(LD_REND, "Descriptor cookie is %lu bytes, but we expected " + "%lu bytes. Dropping cell.", + (unsigned long)cookie_len, (unsigned long)REND_DESC_COOKIE_LEN); + return 0; + } + /* Look up client authorization by descriptor cookie. */ SMARTLIST_FOREACH(service->clients, rend_authorized_client_t *, client, { if (tor_memeq(client->descriptor_cookie, descriptor_cookie, @@ -1330,7 +1339,8 @@ rend_service_introduce(origin_circuit_t *circuit, const uint8_t *request, if (service->clients) { if (parsed_req->version == 3 && parsed_req->u.v3.auth_len > 0) { if (rend_check_authorization(service, - (const char*)parsed_req->u.v3.auth_data)) { + (const char*)parsed_req->u.v3.auth_data, + parsed_req->u.v3.auth_len)) { log_info(LD_REND, "Authorization data in INTRODUCE2 cell are valid."); } else { log_info(LD_REND, "The authorization data that are contained in "