options: added basic SASL XOAUTH2 support

Added the ability to specify an XOAUTH2 bearer token [RFC6750] via the
option CURLOPT_XOAUTH2_BEARER for authentication using RFC6749 "OAuth
2.0 Authorization Framework".

include/curl/curl.h

@@ -1553,6 +1553,9 @@ typedef enum {
    * prototype defines. (Deprecates CURLOPT_PROGRESSFUNCTION) */
   CINIT(XFERINFOFUNCTION, FUNCTIONPOINT, 219),
 
+  /* The XOAUTH2 bearer token */
+  CINIT(XOAUTH2_BEARER, OBJECTPOINT, 220),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 

include/curl/typecheck-gcc.h

@@ -264,6 +264,7 @@ _CURL_WARNING(_curl_easy_getinfo_err_curl_slist,
    (option) == CURLOPT_RTSP_SESSION_ID ||                                     \
    (option) == CURLOPT_RTSP_STREAM_URI ||                                     \
    (option) == CURLOPT_RTSP_TRANSPORT ||                                      \
+   (option) == CURLOPT_XOAUTH2_BEARER ||                                      \
    0)
 
 /* evaluates to true if option takes a curl_write_callback argument */

lib/url.c

@@ -1569,6 +1569,13 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
     result = setstropt(&data->set.str[STRING_PASSWORD],
                        va_arg(param, char *));
     break;
+  case CURLOPT_XOAUTH2_BEARER:
+    /*
+     * XOAUTH2 bearer token to use in the operation
+     */
+    result = setstropt(&data->set.str[STRING_BEARER],
+                       va_arg(param, char *));
+    break;
   case CURLOPT_POSTQUOTE:
     /*
      * List of RAW FTP commands to use after a transfer
@@ -2488,6 +2495,7 @@ static void conn_free(struct connectdata *conn)
 
   Curl_safefree(conn->user);
   Curl_safefree(conn->passwd);
+  Curl_safefree(conn->xoauth2_bearer);
   Curl_safefree(conn->options);
   Curl_safefree(conn->proxyuser);
   Curl_safefree(conn->proxypasswd);
@@ -5181,6 +5189,13 @@ static CURLcode create_conn(struct SessionHandle *data,
     }
   }
 
+  if(data->set.str[STRING_BEARER]) {
+    conn->xoauth2_bearer = strdup(data->set.str[STRING_BEARER]);
+    if(!conn->xoauth2_bearer) {
+      return CURLE_OUT_OF_MEMORY;
+    }
+  }
+
 #ifndef CURL_DISABLE_PROXY
   /*************************************************************
    * Extract the user and password from the authentication string

lib/urldata.h

@@ -876,6 +876,8 @@ struct connectdata {
   char *passwd;  /* password string, allocated */
   char *options; /* options string, allocated */
 
+  char *xoauth2_bearer; /* bearer token for xoauth2, allocated */
+
   char *proxyuser;    /* proxy user name string, allocated */
   char *proxypasswd;  /* proxy password string, allocated */
   curl_proxytype proxytype; /* what kind of proxy that is in use */
@@ -1367,6 +1369,8 @@ enum dupstring {
   STRING_TLSAUTH_PASSWORD,     /* TLS auth <password> */
 #endif
 
+  STRING_BEARER,          /* <bearer>, if used */
+
   /* -- end of strings -- */
   STRING_LAST /* not used, just an end-of-list marker */
 };