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Fix out-of-bounds read in INTRODUCE2 client auth

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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.
This commit is contained in:
John Brooks 2015-04-25 22:52:35 -06:00 committed by Nick Mathewson
parent 6c7720ed49
commit 2b27ce52d2
2 changed files with 18 additions and 4 deletions
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4
changes/bug15823 Normal file
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@ -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.

18
src/or/rendservice.c
View File

@ -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 "