diff options
author | Marcus Huewe <suse-tux@gmx.de> | 2018-05-11 12:24:56 +0200 |
---|---|---|
committer | Matt Caswell <matt@openssl.org> | 2018-06-07 13:08:07 +0100 |
commit | c0a58e034d3eff68ca5e0d36d7b4d147425b0599 (patch) | |
tree | d84101a77b1ab4760bcd788eb6de4de2a0b1b7ac /ssl/ssl_sess.c | |
parent | 0189bf2bbe30d4fa710fe7440ed7f3d8eab039c6 (diff) |
Do not free a session before calling the remove_session_cb
If the remove_session_cb accesses the session's data (for instance,
via SSL_SESSION_get_protocol_version), a potential use after free
can occur. For this, consider the following scenario when adding
a new session via SSL_CTX_add_session:
- The session cache is full
(SSL_CTX_sess_number(ctx) > SSL_CTX_sess_get_cache_size(ctx))
- Only the session cache has a reference to ctx->session_cache_tail
(that is, ctx->session_cache_tail->references == 1)
Since the cache is full, remove_session_lock is called to remove
ctx->session_cache_tail from the cache. That is, it
SSL_SESSION_free()s the session, which free()s the data. Afterwards,
the free()d session is passed to the remove_session_cb. If the callback
accesses the session's data, we have a use after free.
The free before calling the callback behavior was introduced in
commit e4612d02c53cccd24fa97b08fc01250d1238cca1 ("Remove sessions
from external cache, even if internal cache not used.").
CLA: trivial
Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6222)
Diffstat (limited to 'ssl/ssl_sess.c')
-rw-r--r-- | ssl/ssl_sess.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/ssl/ssl_sess.c b/ssl/ssl_sess.c index 525edb3289..0723765366 100644 --- a/ssl/ssl_sess.c +++ b/ssl/ssl_sess.c @@ -769,11 +769,11 @@ static int remove_session_lock(SSL_CTX *ctx, SSL_SESSION *c, int lck) if (lck) CRYPTO_THREAD_unlock(ctx->lock); - if (ret) - SSL_SESSION_free(r); - if (ctx->remove_session_cb != NULL) ctx->remove_session_cb(ctx, c); + + if (ret) + SSL_SESSION_free(r); } else ret = 0; return ret; |