Back-patch libpq support for TLS versions beyond v1.

Since 7.3.2, libpq has been coded in such a way that the only SSL protocol
it would allow was TLS v1.  That approach is looking increasingly obsolete.
In commit 820f08cabdcbb899 we fixed it to allow TLS >= v1, but did not
back-patch the change at the time, partly out of caution and partly because
the question was confused by a contemporary server-side change to reject
the now-obsolete SSL protocol v3.  9.4 has now been out long enough that
it seems safe to assume the change is OK; hence, back-patch into 9.0-9.3.

(I also chose to back-patch some relevant comments added by commit
326e1d73c476a0b5, but did *not* change the server behavior; hence, pre-9.4
servers will continue to allow SSL v3, even though no remotely modern
client will request it.)

Per gripe from Jan Bilek.

diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index f2d65cc9b36b5f48762c723618daff7c71f420ec..a4a70b9539ddd90f999dcb3994206d5ac71877c2 100644 (file)
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -735,6 +735,13 @@ initialize_SSL(void)
 #endif
                SSL_library_init();
                SSL_load_error_strings();
+
+               /*
+                * We use SSLv23_method() because it can negotiate use of the highest
+                * mutually supported protocol version, while alternatives like
+                * TLSv1_2_method() permit only one specific version.  Note that we
+                * don't actually allow SSL v2, only v3 and TLS protocols (see below).
+                */
                SSL_context = SSL_CTX_new(SSLv23_method());
                if (!SSL_context)
                        ereport(FATAL,

diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 09cffe46afbad48113d56234007f414fc38a7444..deb9469c6b2463d4a6773f74e72cf0389073dec3 100644 (file)
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -965,7 +965,13 @@ init_ssl_system(PGconn *conn)
                        SSL_load_error_strings();
                }
 
-               SSL_context = SSL_CTX_new(TLSv1_method());
+               /*
+                * We use SSLv23_method() because it can negotiate use of the highest
+                * mutually supported protocol version, while alternatives like
+                * TLSv1_2_method() permit only one specific version.  Note that we
+                * don't actually allow SSL v2 or v3, only TLS protocols (see below).
+                */
+               SSL_context = SSL_CTX_new(SSLv23_method());
                if (!SSL_context)
                {
                        char       *err = SSLerrmessage();
@@ -980,6 +986,9 @@ init_ssl_system(PGconn *conn)
                        return -1;
                }
 
+               /* Disable old protocol versions */
+               SSL_CTX_set_options(SSL_context, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);
+
                /*
                 * Disable OpenSSL's moving-write-buffer sanity check, because it
                 * causes unnecessary failures in nonblocking send cases.