[PATCH 2/2] http: use credential API to handle proxy authentication

[Knut Franke <k.franke@science-computing.de>]

Currently, the only way to pass proxy credentials to curl is by including them
in the proxy URL. Usually, this means they will end up on disk unencrypted, one
way or another (by inclusion in ~/.gitconfig, shell profile or history). Since
proxy authentication often uses a domain user, credentials can be security
sensitive; therefore, a safer way of passing credentials is desirable.

If the configured proxy contains a username but not a password, query the
credential API for one. Also, make sure we approve/reject proxy credentials
properly.

For consistency reasons, add parsing of http_proxy/https_proxy/all_proxy
environment variables, which would otherwise be evaluated as a fallback by curl.
Without this, we would have different semantics for git configuration and
environment variables.

Signed-off-by: Knut Franke <k.franke@science-computing.de>
---
 http.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 http.h |  1 +
 2 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/http.c b/http.c
index 4756bab..11bebe1 100644
--- a/http.c
+++ b/http.c
@@ -79,6 +79,7 @@ static struct {
 	// curl(1) and is not included in CURLAUTH_ANY, so we leave it out
 	// here, too
 };
+struct credential http_proxy_auth = CREDENTIAL_INIT;
 static const char *curl_cookie_file;
 static int curl_save_cookies;
 struct credential http_auth = CREDENTIAL_INIT;
@@ -176,6 +177,9 @@ static void finish_active_slot(struct active_request_slot *slot)
 #else
 		slot->results->auth_avail = 0;
 #endif
+
+		curl_easy_getinfo(slot->curl, CURLINFO_HTTP_CONNECTCODE,
+			&slot->results->http_connectcode);
 	}
 
 	/* Run callback if appropriate */
@@ -333,6 +337,25 @@ static void copy_from_env(const char **var, const char *envname)
 
 static void init_curl_proxy_auth(CURL *result)
 {
+	if (http_proxy_auth.username) {
+		if (!http_proxy_auth.password) {
+			credential_fill(&http_proxy_auth);
+		}
+#if LIBCURL_VERSION_NUM >= 0x071301
+		curl_easy_setopt(result, CURLOPT_PROXYUSERNAME,
+			http_proxy_auth.username);
+		curl_easy_setopt(result, CURLOPT_PROXYPASSWORD,
+			http_proxy_auth.password);
+#else
+		struct strbuf up = STRBUF_INIT;
+		strbuf_reset(&up);
+		strbuf_addstr_urlencode(&up, http_proxy_auth.username, 1);
+		strbuf_addch(&up, ':');
+		strbuf_addstr_urlencode(&up, http_proxy_auth.password, 1);
+		curl_easy_setopt(result, CURLOPT_PROXYUSERPWD, up.buf);
+#endif
+	}
+
 	copy_from_env(&http_proxy_authmethod, "GIT_HTTP_PROXY_AUTHMETHOD");
 
 	if (http_proxy_authmethod) {
@@ -513,8 +536,36 @@ static CURL *get_curl_handle(void)
 		curl_easy_setopt(result, CURLOPT_USE_SSL, CURLUSESSL_TRY);
 #endif
 
+	/*
+	 * curl also examines these variables as a fallback; but we need to query
+	 * them here in order to decide whether to prompt for missing password (cf.
+	 * init_curl_proxy_auth()).
+	 */
+	if (!curl_http_proxy) {
+		if (!strcmp(http_auth.protocol, "https")) {
+			copy_from_env(&curl_http_proxy, "HTTPS_PROXY");
+			copy_from_env(&curl_http_proxy, "https_proxy");
+		} else {
+			copy_from_env(&curl_http_proxy, "http_proxy");
+		}
+		if (!curl_http_proxy) {
+			copy_from_env(&curl_http_proxy, "ALL_PROXY");
+			copy_from_env(&curl_http_proxy, "all_proxy");
+		}
+	}
+
 	if (curl_http_proxy) {
-		curl_easy_setopt(result, CURLOPT_PROXY, curl_http_proxy);
+		if (strstr(curl_http_proxy, "://"))
+			credential_from_url(&http_proxy_auth, curl_http_proxy);
+		else {
+			struct strbuf url = STRBUF_INIT;
+			strbuf_reset(&url);
+			strbuf_addstr(&url, "http://");
+			strbuf_addstr(&url, curl_http_proxy);
+			credential_from_url(&http_proxy_auth, url.buf);
+		}
+
+		curl_easy_setopt(result, CURLOPT_PROXY, http_proxy_auth.host);
 	}
 	init_curl_proxy_auth(result);
 
@@ -658,6 +709,12 @@ void http_cleanup(void)
 		curl_http_proxy = NULL;
 	}
 
+	if (http_proxy_auth.password) {
+		memset(http_proxy_auth.password, 0, strlen(http_proxy_auth.password));
+		free(http_proxy_auth.password);
+		http_proxy_auth.password = NULL;
+	}
+
 	if (http_proxy_authmethod) {
 		free((void *)http_proxy_authmethod);
 		http_proxy_authmethod = NULL;
@@ -991,6 +1048,8 @@ static int handle_curl_result(struct slot_results *results)
 
 	if (results->curl_result == CURLE_OK) {
 		credential_approve(&http_auth);
+		if (http_proxy_auth.password)
+			credential_approve(&http_proxy_auth);
 		return HTTP_OK;
 	} else if (missing_target(results))
 		return HTTP_MISSING_TARGET;
@@ -1005,6 +1064,8 @@ static int handle_curl_result(struct slot_results *results)
 			return HTTP_REAUTH;
 		}
 	} else {
+		if (results->http_connectcode == 407)
+			credential_reject(&http_proxy_auth);
 #if LIBCURL_VERSION_NUM >= 0x070c00
 		if (!curl_errorstr[0])
 			strlcpy(curl_errorstr,
diff --git a/http.h b/http.h
index 49afe39..7352a9e 100644
--- a/http.h
+++ b/http.h
@@ -54,6 +54,7 @@ struct slot_results {
 	CURLcode curl_result;
 	long http_code;
 	long auth_avail;
+	long http_connectcode;
 };
 
 struct active_request_slot {
-- 
2.3.7

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