Disallow X.509 wildcard matches in domain literals.

2 files changed, 27 insertions, 4 deletions

diff --git a/NEWS b/NEWS
index 9f429a22..a63a3d9c 100644
--- a/NEWS
+++ b/NEWS
@@ -54,6 +54,16 @@ removed from a 6.4.0 or newer release.)
 
 fetchmail-6.3.18 (not yet released):
 
+# SECURITY IMPROVEMENTS TO DEFANG X.509 CERTIFICATE ABUSE
+* Fetchmail now only accepts wildcard certificate common names and subject
+  alternative names if they start with "*.". Previous versions would accept
+  wildcards even if no period followed immediately.
+* Fetchmail now disallows wildcards in certificates to match domain literals
+  (such as 10.9.8.7), or wildcards in domain literals ("*.168.23.23").
+  The test is overly picky and triggers if the pattern (after skipping the
+  initial wildcard "*") or domain consist solely of digits and dots and matches
+  more than needed.
+
 # BUG FIXES
 * Fetchmail would warn about insecure SSL/TLS connections even if a matching
   --sslfingerprint was specified. This is an omission from an SSL usability
@@ -78,9 +88,6 @@ fetchmail-6.3.18 (not yet released):
   credentials. This avoids getting servers such as Exchange 2007 wedged if
   GSSAPI authentication fails.  Reported by Patrick Rynhart, Debian Bug #568455,
   and Alan Murrell, to the fetchmail-users list.
-* Fetchmail now only accepts wildcard certificate common names and subject
-  alternative names if they start with "*.". Previous versions would accept
-  wildcards even if no period followed immediately.
 
 # CHANGES
 * When encountering incorrect headers, fetchmail will refer to the bad-header
diff --git a/socket.c b/socket.c
index 59b0112e..d3cf90d7 100644
--- a/socket.c
+++ b/socket.c
@@ -600,7 +600,23 @@ SSL *SSLGetContext( int sock )
  * The only place where a wildcard is allowed is in the leftmost
  * position of p1. */
 static int name_match(const char *p1, const char *p2) {
-    if (p1[0] == '*' && p1[1] == '.') {
+    const char *const dom = "0123456789.";
+    int wildcard_ok = 1;
+
+    /* blank patterns never match */
+    if (p1[0] == '\0')
+	return 0;
+
+    /* disallow wildcards in certificates for domain literals
+     * (10.9.8.7-like) */
+    if (strspn(p1+(*p1 == '*' ? 1 : 0), dom) == strlen(p1))
+	wildcard_ok = 0;
+
+    /* disallow wildcards for domain literals */
+    if (strspn(p2, dom) == strlen(p2))
+	wildcard_ok = 0;
+
+    if (wildcard_ok && p1[0] == '*' && p1[1] == '.') {
 	size_t l1, l2;
 
 	++p1;