TLS: library version build-time checks for resumption support

3 files changed, 15 insertions, 4 deletions

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index a2861c4a9..feecb3375 100644
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -953,9 +953,10 @@ Transport configurations should be checked for this.  An example avoidance:
 
 TLS Session Resumption
 ----------------------
-TLS Session Resumption for TLS 1.2 and TLS1.3 connections can be used (defined
+TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
 in RFC 5077 for 1.2).  The support for this can be included by building with
-EXPERIMENTAL_TLS_RESUME defined.
+EXPERIMENTAL_TLS_RESUME defined.  This requires GnuTLS 3.6.3 or OpenSSL 1.1.1
+(or later).
 
 Session resumption (this is the "stateless" variant) involves the server sending
 a "session ticket" to the client on one connection, which can be stored by the
diff --git a/src/src/tls-gnu.c b/src/src/tls-gnu.c
index 03002c704..085f6b840 100644
--- a/src/src/tls-gnu.c
+++ b/src/src/tls-gnu.c
@@ -89,6 +89,12 @@ require current GnuTLS, then we'll drop support for the ancient libraries).
 # endif
 #endif
 
+#ifdef EXPERIMENTAL_TLS_RESUME
+# if GNUTLS_VERSION_NUMBER < 0x030603
+#  error GNUTLS version too early for session-resumption
+# endif
+#endif
+
 #ifndef DISABLE_OCSP
 # include <gnutls/ocsp.h>
 #endif
@@ -2475,7 +2481,6 @@ but this flag is not set until the second.  TLS 1.3 it's the other way about.
 Keep both calls as the session data cannot be extracted before handshake
 completes. */
 
-#ifdef GNUTLS_SFLAGS_SESSION_TICKET
 if (gnutls_session_get_flags(session) & GNUTLS_SFLAGS_SESSION_TICKET)
   {
   gnutls_datum_t tkt;
@@ -2510,7 +2515,6 @@ if (gnutls_session_get_flags(session) & GNUTLS_SFLAGS_SESSION_TICKET)
     else DEBUG(D_tls)
       debug_printf("extract session data: %s\n", US gnutls_strerror(rc));
   }
-#endif
 }
 
 
diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index e47df7cb2..824212dbc 100644
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -108,6 +108,12 @@ change this guard and punt the issue for a while longer. */
 # define DISABLE_OCSP
 #endif
 
+#ifdef EXPERIMENTAL_TLS_RESUME
+# if OPENSSL_VERSION_NUMBER < 0x0101010L
+#  error OpenSSL version too old for session-resumption
+# endif
+#endif
+
 #ifdef EXIM_HAVE_OPENSSL_CHECKHOST
 # include <openssl/x509v3.h>
 #endif