From ce24bec7e2518d4ea7aa931021454d1191f4906b Mon Sep 17 00:00:00 2001 From: Antonio Quartulli Date: Tue, 28 Jun 2022 11:41:44 +0200 Subject: [PATCH] tls-crypt-v2: bail out if the client key is too small The tls-crypt-v2 key should be at least 2 bytes long in order to read the actual length. Bail out if the key is too short. This looks like it could be abused to trigger a read of uninitialized memory, but after close checking it won't: We read from BEND(), so this is defined for TCP since the minimum length there is 3 bytes (pkt len + opcode) For UDP we might read past the beginning of the packet but since they are buffers coming from the packet stack we have the headroom/tailroom, so might read some random data (but not out of bound!). So we copy some more or less random number into net_len/wkc_len but without actually reading from undefined memory. The next line will then almost definitively fail (buf_advance()). While at it improve the error message a bit. Signed-off-by: Antonio Quartulli Acked-by: Arne Schwabe Message-Id: <20220628094144.17471-1-a@unstable.cc> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24580.html Signed-off-by: Gert Doering (cherry picked from commit 462339a45089ef655faf02232d7d792def9b8afb) --- src/openvpn/tls_crypt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/openvpn/tls_crypt.c b/src/openvpn/tls_crypt.c index 663f5e169..f2a97462d 100644 --- a/src/openvpn/tls_crypt.c +++ b/src/openvpn/tls_crypt.c @@ -585,7 +585,8 @@ tls_crypt_v2_extract_client_key(struct buffer *buf, if (BLEN(&wrapped_client_key) < sizeof(net_len)) { - msg(D_TLS_ERRORS, "failed to read length"); + msg(D_TLS_ERRORS, "Can not read tls-crypt-v2 client key length"); + return false; } memcpy(&net_len, BEND(&wrapped_client_key) - sizeof(net_len), sizeof(net_len)); -- 2.47.2