http: check CURLE_SSL_PINNEDPUBKEYNOTMATCH when emitting errors

Change the error shown when a http.pinnedPubKey doesn't match to point
the http.pinnedPubKey variable added in aeff8a6 (http: implement
public key pinning, 2016-02-15), e.g.:

    git -c http.pinnedPubKey=sha256/someNonMatchingKey ls-remote https://github.com/git/git.git
    fatal: unable to access 'https://github.com/git/git.git/' with http.pinnedPubkey configuration: SSL: public key does not match pinned public key!

Before this we'd emit the exact same thing without the " with
http.pinnedPubkey configuration". The advantage of doing this is that
we're going to get a translated message (everything after the ":" is
hardcoded in English in libcurl), and we've got a reference to the
git-specific configuration variable that's causing the error.

Unfortunately we can't test this easily, as there are no tests that
require https:// in the test suite, and t/lib-httpd.sh doesn't know
how to set up such tests. See [1] for the start of a discussion about
what it would take to have divergent "t/lib-httpd/apache.conf" test
setups. #leftoverbits

1. https://lore.kernel.org/git/[email protected]/

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

git-curl-compat.h

@@ -67,10 +67,11 @@
 
 /**
  * CURLOPT_PINNEDPUBLICKEY was added in 7.39.0, released in November
- * 2014.
+ * 2014. CURLE_SSL_PINNEDPUBKEYNOTMATCH was added in that same version.
  */
 #if LIBCURL_VERSION_NUM >= 0x072c00
 #define GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY 1
+#define GIT_CURL_HAVE_CURLE_SSL_PINNEDPUBKEYNOTMATCH 1
 #endif
 
 /**

http.c

@@ -1489,6 +1489,10 @@ static int handle_curl_result(struct slot_results *results)
 		 */
 		credential_reject(&cert_auth);
 		return HTTP_NOAUTH;
+#ifdef GIT_CURL_HAVE_CURLE_SSL_PINNEDPUBKEYNOTMATCH
+	} else if (results->curl_result == CURLE_SSL_PINNEDPUBKEYNOTMATCH) {
+		return HTTP_NOMATCHPUBLICKEY;
+#endif
 	} else if (missing_target(results))
 		return HTTP_MISSING_TARGET;
 	else if (results->http_code == 401) {

http.h

@@ -154,6 +154,7 @@ struct http_get_options {
 #define HTTP_START_FAILED	3
 #define HTTP_REAUTH	4
 #define HTTP_NOAUTH	5
+#define HTTP_NOMATCHPUBLICKEY	6
 
 /*
  * Requests a URL and stores the result in a strbuf.

remote-curl.c

@@ -499,6 +499,10 @@ static struct discovery *discover_refs(const char *service, int for_push)
 		show_http_message(&type, &charset, &buffer);
 		die(_("Authentication failed for '%s'"),
 		    transport_anonymize_url(url.buf));
+	case HTTP_NOMATCHPUBLICKEY:
+		show_http_message(&type, &charset, &buffer);
+		die(_("unable to access '%s' with http.pinnedPubkey configuration: %s"),
+		    transport_anonymize_url(url.buf), curl_errorstr);
 	default:
 		show_http_message(&type, &charset, &buffer);
 		die(_("unable to access '%s': %s"),