http: refactor code to clarify memory ownership

There are various variables assigned via `git_config_string()` and
`git_config_pathname()` which are never free'd. This bug is relatable
because the out parameter of those functions are a `const char **`, even
though memory ownership is transferred to the caller.

We're about to adapt the functions to instead use `char **`. Prepare the
code accordingly. Note that the `(const char **)` casts will go away
once we have adapted the functions.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

http.c

@@ -39,8 +39,8 @@ char curl_errorstr[CURL_ERROR_SIZE];
 static int curl_ssl_verify = -1;
 static int curl_ssl_try;
 static const char *curl_http_version = NULL;
-static const char *ssl_cert;
-static const char *ssl_cert_type;
+static char *ssl_cert;
+static char *ssl_cert_type;
 static const char *ssl_cipherlist;
 static const char *ssl_version;
 static struct {
@@ -59,23 +59,23 @@ static struct {
 	{ "tlsv1.3", CURL_SSLVERSION_TLSv1_3 },
 #endif
 };
-static const char *ssl_key;
-static const char *ssl_key_type;
-static const char *ssl_capath;
-static const char *curl_no_proxy;
+static char *ssl_key;
+static char *ssl_key_type;
+static char *ssl_capath;
+static char *curl_no_proxy;
 #ifdef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
 static const char *ssl_pinnedkey;
 #endif
-static const char *ssl_cainfo;
+static char *ssl_cainfo;
 static long curl_low_speed_limit = -1;
 static long curl_low_speed_time = -1;
 static int curl_ftp_no_epsv;
-static const char *curl_http_proxy;
-static const char *http_proxy_authmethod;
+static char *curl_http_proxy;
+static char *http_proxy_authmethod;
 
-static const char *http_proxy_ssl_cert;
-static const char *http_proxy_ssl_key;
-static const char *http_proxy_ssl_ca_info;
+static char *http_proxy_ssl_cert;
+static char *http_proxy_ssl_key;
+static char *http_proxy_ssl_ca_info;
 static struct credential proxy_cert_auth = CREDENTIAL_INIT;
 static int proxy_ssl_cert_password_required;
 
@@ -112,7 +112,7 @@ static const char *curl_cookie_file;
 static int curl_save_cookies;
 struct credential http_auth = CREDENTIAL_INIT;
 static int http_proactive_auth;
-static const char *user_agent;
+static char *user_agent;
 static int curl_empty_auth = -1;
 
 enum http_follow_config http_follow_config = HTTP_FOLLOW_INITIAL;
@@ -381,17 +381,17 @@ static int http_options(const char *var, const char *value,
 	if (!strcmp("http.sslversion", var))
 		return git_config_string(&ssl_version, var, value);
 	if (!strcmp("http.sslcert", var))
-		return git_config_pathname(&ssl_cert, var, value);
+		return git_config_pathname((const char **)&ssl_cert, var, value);
 	if (!strcmp("http.sslcerttype", var))
-		return git_config_string(&ssl_cert_type, var, value);
+		return git_config_string((const char **)&ssl_cert_type, var, value);
 	if (!strcmp("http.sslkey", var))
-		return git_config_pathname(&ssl_key, var, value);
+		return git_config_pathname((const char **)&ssl_key, var, value);
 	if (!strcmp("http.sslkeytype", var))
-		return git_config_string(&ssl_key_type, var, value);
+		return git_config_string((const char **)&ssl_key_type, var, value);
 	if (!strcmp("http.sslcapath", var))
-		return git_config_pathname(&ssl_capath, var, value);
+		return git_config_pathname((const char **)&ssl_capath, var, value);
 	if (!strcmp("http.sslcainfo", var))
-		return git_config_pathname(&ssl_cainfo, var, value);
+		return git_config_pathname((const char **)&ssl_cainfo, var, value);
 	if (!strcmp("http.sslcertpasswordprotected", var)) {
 		ssl_cert_password_required = git_config_bool(var, value);
 		return 0;
@@ -440,19 +440,19 @@ static int http_options(const char *var, const char *value,
 		return 0;
 	}
 	if (!strcmp("http.proxy", var))
-		return git_config_string(&curl_http_proxy, var, value);
+		return git_config_string((const char **)&curl_http_proxy, var, value);
 
 	if (!strcmp("http.proxyauthmethod", var))
-		return git_config_string(&http_proxy_authmethod, var, value);
+		return git_config_string((const char **)&http_proxy_authmethod, var, value);
 
 	if (!strcmp("http.proxysslcert", var))
-		return git_config_string(&http_proxy_ssl_cert, var, value);
+		return git_config_string((const char **)&http_proxy_ssl_cert, var, value);
 
 	if (!strcmp("http.proxysslkey", var))
-		return git_config_string(&http_proxy_ssl_key, var, value);
+		return git_config_string((const char **)&http_proxy_ssl_key, var, value);
 
 	if (!strcmp("http.proxysslcainfo", var))
-		return git_config_string(&http_proxy_ssl_ca_info, var, value);
+		return git_config_string((const char **)&http_proxy_ssl_ca_info, var, value);
 
 	if (!strcmp("http.proxysslcertpasswordprotected", var)) {
 		proxy_ssl_cert_password_required = git_config_bool(var, value);
@@ -476,7 +476,7 @@ static int http_options(const char *var, const char *value,
 	}
 
 	if (!strcmp("http.useragent", var))
-		return git_config_string(&user_agent, var, value);
+		return git_config_string((const char **)&user_agent, var, value);
 
 	if (!strcmp("http.emptyauth", var)) {
 		if (value && !strcmp("auto", value))
@@ -592,10 +592,10 @@ static void init_curl_http_auth(CURL *result)
 }
 
 /* *var must be free-able */
-static void var_override(const char **var, char *value)
+static void var_override(char **var, char *value)
 {
 	if (value) {
-		free((void *)*var);
+		free(*var);
 		*var = xstrdup(value);
 	}
 }
@@ -1233,11 +1233,13 @@ static CURL *get_curl_handle(void)
 	return result;
 }
 
-static void set_from_env(const char **var, const char *envname)
+static void set_from_env(char **var, const char *envname)
 {
 	const char *val = getenv(envname);
-	if (val)
-		*var = val;
+	if (val) {
+		FREE_AND_NULL(*var);
+		*var = xstrdup(val);
+	}
 }
 
 void http_init(struct remote *remote, const char *url, int proactive_auth)