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EAP-SIM/AKA: Fix check for anonymous decorated identity

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eap_sim_anonymous_username() gets called with an argument that is not a
null terminated C string and as such, os_strrchr() and os_strlen()
cannot be used with it. The previous implementation resulted in use of
uninitialized values and a potential read beyond the end of the buffer.

Credit to OSS-Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=32277
Fixes: 73d9891bd7 ("EAP-SIM/AKA peer: Support decorated anonymous identity prefix")
Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2021-03-20 16:25:50 +02:00
parent 512d973cc2
commit 3ae18d4bd7
1 changed files with 18 additions and 4 deletions
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22
src/eap_common/eap_sim_common.c
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@ -1210,10 +1210,24 @@ void eap_sim_report_notification(void *msg_ctx, int notification, int aka)
} }
static const u8 * get_last_char(const u8 *val, size_t len, char c)
{
while (len > 0) {
const u8 *pos = &val[len - 1];
if (*pos == (u8) c)
return pos;
len--;
}
return NULL;
}
int eap_sim_anonymous_username(const u8 *id, size_t id_len) int eap_sim_anonymous_username(const u8 *id, size_t id_len)
{ {
static const char *anonymous_id_prefix = "anonymous@"; static const char *anonymous_id_prefix = "anonymous@";
const char *decorated; const u8 *decorated;
size_t anonymous_id_len = os_strlen(anonymous_id_prefix); size_t anonymous_id_len = os_strlen(anonymous_id_prefix);
if (id_len > anonymous_id_len && if (id_len > anonymous_id_len &&
@ -1229,11 +1243,11 @@ int eap_sim_anonymous_username(const u8 *id, size_t id_len)
/* RFC 7542 decorated username, for example: /* RFC 7542 decorated username, for example:
* homerealm.example.org!anonymous@otherrealm.example.net */ * homerealm.example.org!anonymous@otherrealm.example.net */
decorated = os_strrchr((const char *) id, '!'); decorated = get_last_char(id, id_len, '!');
if (decorated) { if (decorated) {
decorated++; decorated++;
return eap_sim_anonymous_username((const u8 *) decorated, return eap_sim_anonymous_username(decorated,
os_strlen(decorated)); id + id_len - decorated);
} }
return 0; return 0;