[PATCH v3] http: add support for specifying an SSL cipher list

[Lars Kellogg-Stedman <lars@redhat.com>]

Teach git about a new option, "http.sslCipherList", which permits one to
specify a list of ciphers to use when negotiating SSL connections.  The
setting can be overwridden by the GIT_SSL_CIPHER_LIST environment
variable.

Signed-off-by: Lars Kellogg-Stedman <lars@redhat.com>
---

This addresses (I hope!) comments from Junio and Ray, and also resolves some
whitespace issues present in the earlier version of the patch.

 Documentation/config.txt | 13 +++++++++++++
 http.c                   | 14 ++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 2e5ceaf..b982d66 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1560,6 +1560,19 @@ http.saveCookies::
 	If set, store cookies received during requests to the file specified by
 	http.cookieFile. Has no effect if http.cookieFile is unset.
 
+http.sslCipherList::
+	A list of SSL ciphers to use when negotiating an SSL connection.
+	The available ciphers depend on whether libcurl was built against
+	NSS or OpenSSL and the particular configuration of the crypto
+	library in use.  Internally this sets the CURLOPT_SSL_CIPHER_LIST
+	option; see the libcurl documentation for that option for more
+	details on the format of this list.
+
+	Can be overridden by the 'GIT_SSL_CIPHER_LIST' environment variable.
+	To force git to use libcurl's default cipher list and ignore any
+	explicit http.sslCipherList option, set GIT_SSL_CIPHER_LIST to the
+	empty string.
+
 http.sslVerify::
 	Whether to verify the SSL certificate when fetching or pushing
 	over HTTPS. Can be overridden by the 'GIT_SSL_NO_VERIFY' environment
diff --git a/http.c b/http.c
index 4b179f6..b617546 100644
--- a/http.c
+++ b/http.c
@@ -36,6 +36,7 @@ char curl_errorstr[CURL_ERROR_SIZE];
 static int curl_ssl_verify = -1;
 static int curl_ssl_try;
 static const char *ssl_cert;
+static const char *ssl_cipherlist;
 #if LIBCURL_VERSION_NUM >= 0x070903
 static const char *ssl_key;
 #endif
@@ -187,6 +188,9 @@ static int http_options(const char *var, const char *value, void *cb)
 		curl_ssl_verify = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp("http.sslcipherlist", var)) {
+		return git_config_string(&ssl_cipherlist, var, value);
+	}
 	if (!strcmp("http.sslcert", var))
 		return git_config_string(&ssl_cert, var, value);
 #if LIBCURL_VERSION_NUM >= 0x070903
@@ -361,6 +365,16 @@ static CURL *get_curl_handle(void)
 	if (http_proactive_auth)
 		init_curl_http_auth(result);
 
+	if (getenv("GIT_SSL_CIPHER_LIST"))
+		ssl_cipherlist = getenv("GIT_SSL_CIPHER_LIST");
+
+	/* See http://curl.haxx.se/libcurl/c/CURLOPT_SSL_CIPHER_LIST.html
+	 * for details on the format of and available values for
+	 * CURLOPT_SSL_CIPHER_LIST. */
+	if (ssl_cipherlist != NULL && ssl_cipherlist[0] != '\0')
+		curl_easy_setopt(result, CURLOPT_SSL_CIPHER_LIST,
+				ssl_cipherlist);
+
 	if (ssl_cert != NULL)
 		curl_easy_setopt(result, CURLOPT_SSLCERT, ssl_cert);
 	if (has_cert_password())
-- 
2.4.0