- 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!

include/curl/curl.h

@@ -1135,6 +1135,11 @@ typedef enum {
   /* (IPv6) Address scope */
   CINIT(ADDRESS_SCOPE, LONG, 171),
 
+  /* Collect certificate chain info and allow it to get retrievable with
+     CURLINFO_CERTINFO after the transfer is complete. (Unfortunately) only
+     working with OpenSSL-powered builds. */
+  CINIT(CERTINFO, LONG, 172),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 
@@ -1491,6 +1496,15 @@ CURL_EXTERN void curl_slist_free_all(struct curl_slist *);
  */
 CURL_EXTERN time_t curl_getdate(const char *p, const time_t *unused);
 
+/* info about the certificate chain, only for OpenSSL builds. Asked
+   for with CURLOPT_CERTINFO / CURLINFO_CERTINFO */
+struct curl_certinfo {
+  int num_of_certs;             /* number of certificates with information */
+  struct curl_slist **certinfo; /* for each index in this array, there's a
+                                   linked list with textual information in the
+                                   format "name: value" */
+};
+
 #define CURLINFO_STRING   0x100000
 #define CURLINFO_LONG     0x200000
 #define CURLINFO_DOUBLE   0x300000
@@ -1533,9 +1547,10 @@ typedef enum {
   CURLINFO_REDIRECT_URL     = CURLINFO_STRING + 31,
   CURLINFO_PRIMARY_IP       = CURLINFO_STRING + 32,
   CURLINFO_APPCONNECT_TIME  = CURLINFO_DOUBLE + 33,
+  CURLINFO_CERTINFO         = CURLINFO_SLIST  + 34,
   /* Fill in new entries below here! */
 
-  CURLINFO_LASTONE          = 33
+  CURLINFO_LASTONE          = 34
 } CURLINFO;
 
 /* CURLINFO_RESPONSE_CODE is the new name for the option previously known as