schannel: add support for CURLOPT_CAINFO

- Move verify_certificate functionality in schannel.c into a new
  file called schannel_verify.c. Additionally, some structure defintions
  from schannel.c have been moved to schannel.h to allow them to be
  used in schannel_verify.c.

- Make verify_certificate functionality for Schannel available on
  all versions of Windows instead of just Windows CE. verify_certificate
  will be invoked on Windows CE or when the user specifies
  CURLOPT_CAINFO and CURLOPT_SSL_VERIFYPEER.

- In verify_certificate, create a custom certificate chain engine that
  exclusively trusts the certificate store backed by the CURLOPT_CAINFO
  file.

- doc updates of --cacert/CAINFO support for schannel

- Use CERT_NAME_SEARCH_ALL_NAMES_FLAG when invoking CertGetNameString
  when available. This implements a TODO in schannel.c to improve
  handling of multiple SANs in a certificate. In particular, all SANs
  will now be searched instead of just the first name.

- Update tool_operate.c to not search for the curl-ca-bundle.crt file
  when using Schannel to maintain backward compatibility. Previously,
  any curl-ca-bundle.crt file found in that search would have been
  ignored by Schannel. But, with CAINFO support, the file found by
  that search would have been used as the certificate store and
  could cause issues for any users that have curl-ca-bundle.crt in
  the search path.

- Update url.c to not set the build time CURL_CA_BUNDLE if the selected
  SSL backend is Schannel. We allow setting CA location for schannel
  only when explicitly specified by the user via CURLOPT_CAINFO /
  --cacert.

- Add new test cases 3000 and 3001. These test cases check that the first
  and last SAN, respectively, matches the connection hostname. New test
  certificates have been added for these cases. For 3000, the certificate
  prefix is Server-localhost-firstSAN and for 3001, the certificate
  prefix is Server-localhost-secondSAN.

- Remove TODO 15.2 (Add support for custom server certificate
  validation), this commit addresses it.

Closes https://github.com/curl/curl/pull/1325

1 files changed, 21 insertions, 13 deletions

diff --git a/lib/url.c b/lib/url.c
index 8c9c69141..2491fa2da 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -488,25 +488,33 @@ CURLcode Curl_init_userdefined(struct Curl_easy *data)
   set->socks5_gssapi_nec = FALSE;
 #endif
 
-  /* This is our preferred CA cert bundle/path since install time */
+  /* Set the default CA cert bundle/path detected/specified at build time.
+   *
+   * If Schannel (WinSSL) is the selected SSL backend then these locations
+   * are ignored. We allow setting CA location for schannel only when
+   * explicitly specified by the user via CURLOPT_CAINFO / --cacert.
+   */
+  if(Curl_ssl_backend() != CURLSSLBACKEND_SCHANNEL) {
 #if defined(CURL_CA_BUNDLE)
-  result = Curl_setstropt(&set->str[STRING_SSL_CAFILE_ORIG], CURL_CA_BUNDLE);
-  if(result)
-    return result;
+    result = Curl_setstropt(&set->str[STRING_SSL_CAFILE_ORIG], CURL_CA_BUNDLE);
+    if(result)
+      return result;
 
-  result = Curl_setstropt(&set->str[STRING_SSL_CAFILE_PROXY], CURL_CA_BUNDLE);
-  if(result)
-    return result;
+    result = Curl_setstropt(&set->str[STRING_SSL_CAFILE_PROXY],
+                            CURL_CA_BUNDLE);
+    if(result)
+      return result;
 #endif
 #if defined(CURL_CA_PATH)
-  result = Curl_setstropt(&set->str[STRING_SSL_CAPATH_ORIG], CURL_CA_PATH);
-  if(result)
-    return result;
+    result = Curl_setstropt(&set->str[STRING_SSL_CAPATH_ORIG], CURL_CA_PATH);
+    if(result)
+      return result;
 
-  result = Curl_setstropt(&set->str[STRING_SSL_CAPATH_PROXY], CURL_CA_PATH);
-  if(result)
-    return result;
+    result = Curl_setstropt(&set->str[STRING_SSL_CAPATH_PROXY], CURL_CA_PATH);
+    if(result)
+      return result;
 #endif
+  }
 
   set->wildcard_enabled = FALSE;
   set->chunk_bgn      = ZERO_NULL;