http: implement public key pinning

Add the http.pinnedpubkey configuration option for public key
pinning. It allows any string supported by libcurl --
base64(sha256(pubkey)) or filename of the full public key.

If cURL does not support pinning (is too old) output a warning to the
user.

Signed-off-by: Christoph Egger <christoph@christoph-egger.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config.txt b/Documentation/config.txt
index f61788668e89b659439e2fa5d600aebabdd733a5..bc0237fd6257431945860f0a51b3d414189f739d 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1679,6 +1679,14 @@ http.sslCAPath::
        with when fetching or pushing over HTTPS. Can be overridden
        by the 'GIT_SSL_CAPATH' environment variable.
 
+http.pinnedpubkey::
+       Public key of the https service. It may either be the filename of
+       a PEM or DER encoded public key file or a string starting with
+       'sha256//' followed by the base64 encoded sha256 hash of the
+       public key. See also libcurl 'CURLOPT_PINNEDPUBLICKEY'. git will
+       exit with an error if this option is set but not supported by
+       cURL.
+
 http.sslTry::
        Attempt to use AUTH SSL/TLS and encrypted data transfers
        when connecting via regular FTP protocol. This might be needed

diff --git a/http.c b/http.c
index 0da9e6639832a493f932e3ba332683d3d4ae73ae..34750401078be6afe9d464ee2b26f91490458613 100644 (file)
--- a/http.c
+++ b/http.c
@@ -57,6 +57,9 @@ static const char *ssl_key;
 #if LIBCURL_VERSION_NUM >= 0x070908
 static const char *ssl_capath;
 #endif
+#if LIBCURL_VERSION_NUM >= 0x072c00
+static const char *ssl_pinnedkey;
+#endif
 static const char *ssl_cainfo;
 static long curl_low_speed_limit = -1;
 static long curl_low_speed_time = -1;
@@ -273,6 +276,14 @@ static int http_options(const char *var, const char *value, void *cb)
        if (!strcmp("http.useragent", var))
                return git_config_string(&user_agent, var, value);
 
+       if (!strcmp("http.pinnedpubkey", var)) {
+#if LIBCURL_VERSION_NUM >= 0x072c00
+               return git_config_pathname(&ssl_pinnedkey, var, value);
+#else
+               warning(_("Public key pinning not supported with cURL < 7.44.0"));
+               return 0;
+#endif
+       }
        /* Fall back on the default ones */
        return git_default_config(var, value, cb);
 }
@@ -414,6 +425,10 @@ static CURL *get_curl_handle(void)
 #if LIBCURL_VERSION_NUM >= 0x070908
        if (ssl_capath != NULL)
                curl_easy_setopt(result, CURLOPT_CAPATH, ssl_capath);
+#endif
+#if LIBCURL_VERSION_NUM >= 0x072c00
+       if (ssl_pinnedkey != NULL)
+               curl_easy_setopt(result, CURLOPT_PINNEDPUBLICKEY, ssl_pinnedkey);
 #endif
        if (ssl_cainfo != NULL)
                curl_easy_setopt(result, CURLOPT_CAINFO, ssl_cainfo);