[PATCH] http: check CURLE_SSL_PINNEDPUBKEYNOTMATCH when emitting errors

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change the error shown when a http.pinnedPubKey doesn't match to point
the http.pinnedPubKey variable added in aeff8a61216 (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/YUonS1uoZlZEt+Yd@coredump.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---

I had this waiting on the now-landed ab/http-drop-old-curl-plus due to
adding a new entry to git-curl-compat.h.

 git-curl-compat.h | 3 ++-
 http.c            | 4 ++++
 http.h            | 1 +
 remote-curl.c     | 4 ++++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/git-curl-compat.h b/git-curl-compat.h
index a308bdb3b9b..56a83b6bbd8 100644
--- a/git-curl-compat.h
+++ b/git-curl-compat.h
@@ -64,16 +64,17 @@
 #if LIBCURL_VERSION_NUM >= 0x072200
 #define GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_0
 #endif
 
 /**
  * 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
 
 /**
  * CURL_HTTP_VERSION_2 was added in 7.43.0, released in June 2015.
  *
  * The CURL_HTTP_VERSION_2 alias (but not CURL_HTTP_VERSION_2_0) has
diff --git a/http.c b/http.c
index d7c20493d7f..b6735b51c31 100644
--- a/http.c
+++ b/http.c
@@ -1486,12 +1486,16 @@ static int handle_curl_result(struct slot_results *results)
 		 * certificate, bad password, or something else wrong
 		 * with the certificate.  So we reject the credential to
 		 * avoid caching or saving a bad password.
 		 */
 		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) {
 		if (http_auth.username && http_auth.password) {
 			credential_reject(&http_auth);
 			return HTTP_NOAUTH;
diff --git a/http.h b/http.h
index 3db5a0cf320..df1590e53a4 100644
--- a/http.h
+++ b/http.h
@@ -151,12 +151,13 @@ struct http_get_options {
 #define HTTP_OK			0
 #define HTTP_MISSING_TARGET	1
 #define HTTP_ERROR		2
 #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.
  *
  * If the result pointer is NULL, a HTTP HEAD request is made instead of GET.
  */
diff --git a/remote-curl.c b/remote-curl.c
index 598cff7cde6..8700dbdc0ac 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -496,12 +496,16 @@ static struct discovery *discover_refs(const char *service, int for_push)
 		die(_("repository '%s' not found"),
 		    transport_anonymize_url(url.buf));
 	case HTTP_NOAUTH:
 		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"),
 		    transport_anonymize_url(url.buf), curl_errorstr);
 	}
 
-- 
2.33.0.1231.g24d802460a8