Fix error handling in be_tls_open_server()

[Sergey Shinderuk]

Hi,

A static analyzer reported a possible pfree(NULL) in 
be_tls_open_server(). Here is a fix. Also handle an error from 
X509_NAME_print_ex().

AFAICS, the error "SSL certificate's distinguished name contains 
embedded null" could not be reached at all, because XN_FLAG_RFC2253 
passed to X509_NAME_print_ex() ensures that null bytes are escaped.

Best regards,

--
Sergey Shinderuk                https://postgrespro.com/diff --git a/src/backend/libpq/be-secure-openssl.c 
b/src/backend/libpq/be-secure-openssl.c
index 658b09988d6..31b6a6eacdf 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -620,8 +620,11 @@ aloop:
                bio = BIO_new(BIO_s_mem());
                if (!bio)
                {
-                       pfree(port->peer_cn);
-                       port->peer_cn = NULL;
+                       if (port->peer_cn != NULL)
+                       {
+                               pfree(port->peer_cn);
+                               port->peer_cn = NULL;
+                       }
                        return -1;
                }
 
@@ -632,12 +635,15 @@ aloop:
                 * which make regular expression matching a bit easier. Also 
note that
                 * it prints the Subject fields in reverse order.
                 */
-               X509_NAME_print_ex(bio, x509name, 0, XN_FLAG_RFC2253);
-               if (BIO_get_mem_ptr(bio, &bio_buf) <= 0)
+               if (X509_NAME_print_ex(bio, x509name, 0, XN_FLAG_RFC2253) == -1 
||
+                       BIO_get_mem_ptr(bio, &bio_buf) <= 0)
                {
                        BIO_free(bio);
-                       pfree(port->peer_cn);
-                       port->peer_cn = NULL;
+                       if (port->peer_cn != NULL)
+                       {
+                               pfree(port->peer_cn);
+                               port->peer_cn = NULL;
+                       }
                        return -1;
                }
                peer_dn = MemoryContextAlloc(TopMemoryContext, bio_buf->length 
+ 1);
@@ -651,8 +657,11 @@ aloop:
                                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                         errmsg("SSL certificate's 
distinguished name contains embedded null")));
                        pfree(peer_dn);
-                       pfree(port->peer_cn);
-                       port->peer_cn = NULL;
+                       if (port->peer_cn != NULL)
+                       {
+                               pfree(port->peer_cn);
+                               port->peer_cn = NULL;
+                       }
                        return -1;
                }