On Fri, Jun 10, 2022 at 07:17:45AM -0400, Wietse Venema wrote:
> Specifically, google 0A000126, the first result is PHP issue 8369a
> which links to https://github.com/openssl/openssl/issues/11378. The
> latter had a breaking fix, backed it out for OpenSSL 1.1.1, but
> kept it in the branch that become OpenSSL 3.
I guess that makes for a bit of bitrot to handle in the Postfix TLS
layer. We need to add "SSL_OP_IGNORE_UNEXPECTED_EOF" to the SSL options
when defined (OpenSSL 3.0 and later).
--
Viktor.
--- src/tls/tls.h
+++ src/tls/tls.h
@@ -387,6 +387,13 @@ extern void tls_param_init(void);
#define SSL_OP_NO_TLSv1_3 0L /* Noop */
#endif
+/*
+ * Always used when defined, SMTP has no trucation attacks.
+ */
+#ifndef SSL_OP_IGNORE_UNEXPECTED_EOF
+#define SSL_OP_IGNORE_UNEXPECTED_EOF 0L
+#endif
+
#define TLS_KNOWN_PROTOCOLS \
( TLS_PROTOCOL_SSLv2 | TLS_PROTOCOL_SSLv3 | TLS_PROTOCOL_TLSv1 \
| TLS_PROTOCOL_TLSv1_1 | TLS_PROTOCOL_TLSv1_2 | TLS_PROTOCOL_TLSv1_3
)
@@ -403,7 +410,8 @@ extern void tls_param_init(void);
* just exposed via hex codes or named elements of tls_ssl_options.
*/
#define TLS_SSL_OP_MANAGED_BITS \
- (SSL_OP_CIPHER_SERVER_PREFERENCE | TLS_SSL_OP_PROTOMASK(~0))
+ (SSL_OP_CIPHER_SERVER_PREFERENCE | SSL_OP_IGNORE_UNEXPECTED_EOF | \
+ TLS_SSL_OP_PROTOMASK(~0))
extern int tls_proto_mask_lims(const char *, int *, int *);
--- src/tls/tls_client.c
+++ src/tls/tls_client.c
@@ -713,6 +713,16 @@ TLS_APPL_STATE *tls_client_init(const
TLS_CLIENT_INIT_PROPS *props)
}
tls_dane_digest_init(client_ctx, fpt_alg);
+ /*
+ * Presently we use TLS only with SMTP where truncation attacks are not
+ * possible as a result of application framing. If we ever use TLS in
+ * some other application protocol where truncation could be relevant,
+ * we'd need to disable truncation detection conditionally, or expcitly
+ * clear the option in that code path.
+ *
+ */
+ off |= SSL_OP_IGNORE_UNEXPECTED_EOF;
+
/*
* Protocol selection is destination dependent, so we delay the protocol
* selection options to the per-session SSL object.
--- src/tls/tls_server.c
+++ src/tls/tls_server.c
@@ -512,6 +512,16 @@ TLS_APPL_STATE *tls_server_init(const
TLS_SERVER_INIT_PROPS *props)
if (scache_timeout <= 0)
cachable = 0;
+ /*
+ * Presently we use TLS only with SMTP where truncation attacks are not
+ * possible as a result of application framing. If we ever use TLS in
+ * some other application protocol where truncation could be relevant,
+ * we'd need to disable truncation detection conditionally, or expcitly
+ * clear the option in that code path.
+ *
+ */
+ off |= SSL_OP_IGNORE_UNEXPECTED_EOF;
+
/*
* Protocol work-arounds, OpenSSL version dependent.
*/
