Handle curl_easy_reset() calls when impersonating (#44)

curl_easy_reset() may be used by an application to reset the options on
a curl handle. If an app has the CURL_IMPERSONATE env var defined, then
the impersonation options are automatically set in curl_easy_init() but
will be cleared in a call to curl_easy_reset(). The desired behavior is
for the impersonation options to be retained (as they are "transparent"
to the user), which this commit takes care of.

Note that this only has an effect when libcurl-impersonate is loaded and
the CURL_IMPERSONATE env var is set. Otherwise the regular behavior of
resetting all the handle options is retained.

Test that the unique TLS signature of curl-impersonate is preserved
after a call to curl_easy_reset() when libcurl-impersonate is loaded.
For this purpose change the 'minicurl' testing util to support multiple
URLs and launch it with 2 different URLs when testing the TLS signature.

tests/minicurl.c

@@ -16,13 +16,15 @@
 
 #include <curl/curl.h>
 
+/* Support up to 16 URLs */
+#define MAX_URLS 16
 /* Command line options. */
 struct opts {
     char *outfile;
     uint16_t local_port_start;
     uint16_t local_port_end;
     bool insecure;
-    char *url;
+    char *urls[MAX_URLS];
 };
 
 int parse_ports_range(char *str, uint16_t *start, uint16_t *end)
@@ -60,6 +62,7 @@ int parse_opts(int argc, char **argv, struct opts *opts)
 {
     int c;
     int r;
+    int i;
 
     memset(opts, 0, sizeof(*opts));
 
@@ -94,17 +97,69 @@ int parse_opts(int argc, char **argv, struct opts *opts)
         }
     }
 
-    if (optind < argc) {
-        opts->url = argv[optind++];
-    } else {
+    /* No URL supplied. */
+    if (optind >= argc) {
         return 1;
     }
 
-    if (optind < argc) {
-        /* Too many arguments. */
+    /* The rest of the options are URLs */
+    i = 0;
+    while (optind < argc) {
+        opts->urls[i++] = argv[optind++];
+    }
+
+    return 0;
+}
+
+/* Set all options except for the URL. */
+int set_opts(CURL *curl, struct opts *opts, FILE *file)
+{
+    CURLcode c;
+
+    c = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite);
+    if (c) {
+        fprintf(stderr, "curl_easy_setopt(CURLOPT_WRITEFUNCTION) failed\n");
         return 1;
     }
 
+    c = curl_easy_setopt(curl, CURLOPT_WRITEDATA, file);
+    if (c) {
+        fprintf(stderr, "curl_easy_setopt(CURLOPT_WRITEDATA) failed\n");
+        return 1;
+    }
+
+    if (opts->local_port_start && opts->local_port_end) {
+        c = curl_easy_setopt(curl,
+                             CURLOPT_LOCALPORT,
+                             opts->local_port_start);
+        if (c) {
+            fprintf(stderr, "curl_easy_setopt(CURLOPT_LOCALPORT) failed\n");
+            return 1;
+        }
+
+        c = curl_easy_setopt(curl,
+                             CURLOPT_LOCALPORTRANGE,
+                             opts->local_port_end - opts->local_port_start);
+        if (c) {
+            fprintf(stderr,
+                    "curl_easy_setopt(CURLOPT_LOCALPORTRANGE) failed\n");
+            return 1;
+        }
+    }
+
+    if (opts->insecure) {
+        c = curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
+        if (c) {
+            fprintf(stderr, "curl_easy_setopt(CURLOPT_SSL_VERIFYPEER) failed\n");
+            return 1;
+        }
+        c = curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);
+        if (c) {
+            fprintf(stderr, "curl_easy_setopt(CURLOPT_SSL_VERIFYHOST) failed\n");
+            return 1;
+        }
+    }
+
     return 0;
 }
 
@@ -114,6 +169,7 @@ int main(int argc, char *argv[])
     CURLcode c;
     CURL *curl = NULL;
     FILE *file;
+    int i;
 
     if (parse_opts(argc, argv, &opts)) {
         fprintf(stderr, "Invalid arguments\n");
@@ -143,60 +199,25 @@ int main(int argc, char *argv[])
         goto out;
     }
 
-    c = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite);
-    if (c) {
-        fprintf(stderr, "curl_easy_setopt(CURLOPT_WRITEFUNCTION) failed\n");
-        goto out;
-    }
-
-    c = curl_easy_setopt(curl, CURLOPT_WRITEDATA, file);
-    if (c) {
-        fprintf(stderr, "curl_easy_setopt(CURLOPT_WRITEDATA) failed\n");
-        goto out;
-    }
-
-    if (opts.local_port_start && opts.local_port_end) {
-        c = curl_easy_setopt(curl,
-                             CURLOPT_LOCALPORT,
-                             opts.local_port_start);
-        if (c) {
-            fprintf(stderr, "curl_easy_setopt(CURLOPT_LOCALPORT) failed\n");
+    for (i = 0; i <= MAX_URLS && opts.urls[i]; i++) {
+        if (set_opts(curl, &opts, file)) {
             goto out;
         }
 
-        c = curl_easy_setopt(curl,
-                             CURLOPT_LOCALPORTRANGE,
-                             opts.local_port_end - opts.local_port_start);
+        c = curl_easy_setopt(curl, CURLOPT_URL, opts.urls[i]);
         if (c) {
-            fprintf(stderr,
-                    "curl_easy_setopt(CURLOPT_LOCALPORTRANGE) failed\n");
+            fprintf(stderr, "curl_easy_setopt(CURLOPT_URL) failed\n");
             goto out;
         }
-    }
 
-    if (opts.insecure) {
-        c = curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
+        c = curl_easy_perform(curl);
         if (c) {
-            fprintf(stderr, "curl_easy_setopt(CURLOPT_SSL_VERIFYPEER) failed\n");
+            fprintf(stderr, "curl_easy_perform() failed\n");
             goto out;
         }
-        c = curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);
-        if (c) {
-            fprintf(stderr, "curl_easy_setopt(CURLOPT_SSL_VERIFYHOST) failed\n");
-            goto out;
-        }
-    }
 
-    c = curl_easy_setopt(curl, CURLOPT_URL, opts.url);
-    if (c) {
-        fprintf(stderr, "curl_easy_setopt(CURLOPT_URL) failed\n");
-        goto out;
-    }
-
-    c = curl_easy_perform(curl);
-    if (c) {
-        fprintf(stderr, "curl_easy_perform() failed\n");
-        goto out;
+        /* Re-use the curl handle. */
+        curl_easy_reset(curl);
     }
 
     c = 0;