changeset 29449:5b71a8d7f7ff

sslutil: emit warning when no CA certificates loaded

If no CA certificates are loaded, that is almost certainly a/the
reason certificate verification fails when connecting to a server.

The modern ssl module in Python 2.7.9+ provides an API to access
the list of loaded CA certificates. This patch emits a warning
on modern Python when certificate verification fails and there are
no loaded CA certificates.

There is no way to detect the number of loaded CA certificates
unless the modern ssl module is present. Hence the differences
in test output depending on whether modern ssl is available.

It's worth noting that a test which specifies a CA file still
renders this warning. That is because the certificate it is loading
is a x509 client certificate and not a CA certificate. This
test could be updated if anyone is so inclined.

--- a/mercurial/sslutil.py	Wed Jun 29 19:49:39 2016 -0700
+++ b/mercurial/sslutil.py	Wed Jun 29 19:43:27 2016 -0700
@@ -284,7 +284,22 @@
     else:
         caloaded = False
 
-    sslsocket = sslcontext.wrap_socket(sock, server_hostname=serverhostname)
+    try:
+        sslsocket = sslcontext.wrap_socket(sock, server_hostname=serverhostname)
+    except ssl.SSLError:
+        # If we're doing certificate verification and no CA certs are loaded,
+        # that is almost certainly the reason why verification failed. Provide
+        # a hint to the user.
+        # Only modern ssl module exposes SSLContext.get_ca_certs() so we can
+        # only show this warning if modern ssl is available.
+        if (caloaded and settings['verifymode'] == ssl.CERT_REQUIRED and
+            modernssl and not sslcontext.get_ca_certs()):
+            ui.warn(_('(an attempt was made to load CA certificates but none '
+                      'were loaded; see '
+                      'https://mercurial-scm.org/wiki/SecureConnections for '
+                      'how to configure Mercurial to avoid this error)\n'))
+        raise
+
     # check if wrap_socket failed silently because socket had been
     # closed
     # - see http://bugs.python.org/issue13721

--- a/tests/test-https.t	Wed Jun 29 19:49:39 2016 -0700
+++ b/tests/test-https.t	Wed Jun 29 19:43:27 2016 -0700
@@ -49,6 +49,7 @@
 
 #if defaultcacerts
   $ hg clone https://localhost:$HGPORT/ copy-pull
+  (an attempt was made to load CA certificates but none were loaded; see https://mercurial-scm.org/wiki/SecureConnections for how to configure Mercurial to avoid this error)
   abort: error: *certificate verify failed* (glob)
   [255]
 #else
@@ -80,9 +81,17 @@
 
 A per-host certificate mismatching the server will fail verification
 
+(modern ssl is able to discern whether the loaded cert is a CA cert)
+#if sslcontext
+  $ hg --config hostsecurity.localhost:verifycertsfile="$CERTSDIR/client-cert.pem" clone https://localhost:$HGPORT/
+  (an attempt was made to load CA certificates but none were loaded; see https://mercurial-scm.org/wiki/SecureConnections for how to configure Mercurial to avoid this error)
+  abort: error: *certificate verify failed* (glob)
+  [255]
+#else
   $ hg --config hostsecurity.localhost:verifycertsfile="$CERTSDIR/client-cert.pem" clone https://localhost:$HGPORT/
   abort: error: *certificate verify failed* (glob)
   [255]
+#endif
 
 A per-host certificate matching the server's cert will be accepted
 

--- a/tests/test-patchbomb-tls.t	Wed Jun 29 19:49:39 2016 -0700
+++ b/tests/test-patchbomb-tls.t	Wed Jun 29 19:43:27 2016 -0700
@@ -48,6 +48,7 @@
   this patch series consists of 1 patches.
   
   
+  (an attempt was made to load CA certificates but none were loaded; see https://mercurial-scm.org/wiki/SecureConnections for how to configure Mercurial to avoid this error)
   (?i)abort: .*?certificate.verify.failed.* (re)
   [255]
 #endif