- Introducing CURLOPT_CERTINFO and the corresponding CURLINFO_CERTINFO. By

enabling this feature with CURLOPT_CERTINFO for a request using SSL (HTTPS
  or FTPS), libcurl will gather lots of server certificate info and that info
  can then get extracted by a client after the request has completed with
  curl_easy_getinfo()'s CURLINFO_CERTINFO option. Linus Nielsen Feltzing
  helped me test and smoothen out this feature.

  Unfortunately, this feature currently only works with libcurl built to use
  OpenSSL.

  This feature was sponsored by networking4all.com - thanks!

docs/examples/certinfo.c

@@ -0,0 +1,62 @@
+/*****************************************************************************
+ */
+
+#include <stdio.h>
+
+#include <curl/curl.h>
+#include <curl/types.h>
+#include <curl/easy.h>
+
+static size_t wrfu(void *ptr,  size_t  size,  size_t  nmemb,  void *stream)
+{
+  return size * nmemb;
+}
+int main(int argc, char **argv)
+{
+  CURL *curl;
+  CURLcode res;
+
+  curl_global_init(CURL_GLOBAL_DEFAULT);
+
+  curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://www.networking4all.com/");
+
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, wrfu);
+
+    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
+    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
+
+    curl_easy_setopt(curl, CURLOPT_VERBOSE, 0L);
+    curl_easy_setopt(curl, CURLOPT_CERTINFO, 1L);
+
+    res = curl_easy_perform(curl);
+
+    if(!res) {
+      struct curl_certinfo *ci = NULL;
+
+      res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci);
+
+      if(!res && ci) {
+        int i;
+        printf("%d certs!\n", ci->num_of_certs);
+
+        for(i=0; i<ci->num_of_certs; i++) {
+          struct curl_slist *slist;
+
+          for(slist = ci->certinfo[i]; slist; slist = slist->next)
+            printf("%s\n", slist->data);
+
+        }
+      }
+
+    }
+
+
+    curl_easy_cleanup(curl);
+  }
+
+  curl_global_cleanup();
+
+  return 0;
+}