func_curl.c: Prevent crash when using CURLOPT(httpheader)

Because we use shared thread-local cURL instances, we need to ensure
that the state of the cURL instance is correct before each invocation.

In the case of custom headers, we were not resetting cURL's internal
HTTP header pointer which could result in a crash if subsequent
requests do not configure custom headers.

ASTERISK-29085 #close

Change-Id: I8b4ab34038156dfba613030a45f10e932d2e992d

diff --git a/funcs/func_curl.c b/funcs/func_curl.c
index b6b61819f76add1c37f2ccdf42bae5c637aead7c..3016cc8e3ec58831e62531637d46882fbe1c2944 100644 (file)
--- a/funcs/func_curl.c
+++ b/funcs/func_curl.c
@@ -705,9 +705,10 @@ static int acf_curl_helper(struct ast_channel *chan, const char *cmd, char *info
                curl_easy_setopt(*curl, CURLOPT_POSTFIELDS, args.postdata);
        }
 
-       if (headers) {
-               curl_easy_setopt(*curl, CURLOPT_HTTPHEADER, headers);
-       }
+       /* Always assign the headers - even when NULL - in case we had
+        * custom headers the last time we used this shared cURL
+        * instance */
+       curl_easy_setopt(*curl, CURLOPT_HTTPHEADER, headers);
 
        /* Temporarily assign a buffer for curl to write errors to. */
        curl_errbuf[0] = curl_errbuf[CURL_ERROR_SIZE] = '\0';