The 16-bit name_len field is read directly from the ClientHello and
stored as the sample length without any validation against srv_len,
ext_len, or the channel buffer size. A 65-byte ClientHello with
name_len=0xffff produces a sample claiming 65535 bytes of data when
only ~4 bytes are actually present in the buffer.
Downstream consumers then read tens of kilobytes past the channel
buffer:
- pattern.c:741 XXH3() hashes 65535 bytes -> ~50KB OOB heap read
- sample.c smp_dup memcpy if large trash configured
- log-format %[req.ssl_sni] leaks heap contents to logs/headers
Reachable pre-authentication on any TCP frontend using req.ssl_sni
(req_ssl_sni), which is the documented way to do SNI-based content
switching in TCP mode. No SSL handshake is required; the parser
runs on raw buffer contents in tcp-request content rules.
Bug introduced in commit d4c33c8889ec3 (2013). The ALPN parser in
the same file at line 1044 has the equivalent check; SNI never did.
This must be backported to all supported versions.
---
src/payload.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/payload.c b/src/payload.c
index e1a1583559b1..77734e0f1615 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -874,6 +874,9 @@ smp_fetch_ssl_hello_sni(const struct arg *args, struct
sample *smp, const char *
name_type = data[6];
name_len = (data[7] << 8) + data[8];
+ if (name_len + 3 > srv_len)
+ goto not_ssl_hello;
+
if (name_type == 0) { /* hostname */
smp->data.type = SMP_T_STR;
smp->data.u.str.area = (char *)data + 9;
--
2.53.0
