HTTP "auth done right". See lib/README.httpauth

lib/transfer.c

@@ -193,6 +193,55 @@ checkhttpprefix(struct SessionHandle *data,
   return FALSE;
 }
 
+/*
+ * Curl_readrewind() rewinds the read stream. This typically (so far) only
+ * used for HTTP POST/PUT with multi-pass authentication when a sending was
+ * denied and a resend is necessary.
+ */
+CURLcode Curl_readrewind(struct connectdata *conn)
+{
+  struct SessionHandle *data = conn->data;
+
+  conn->bits.rewindaftersend = FALSE; /* we rewind now */
+
+  /* We have sent away data. If not using CURLOPT_POSTFIELDS or
+     CURLOPT_HTTPPOST, call app to rewind
+  */
+  if(data->set.postfields ||
+     (data->set.httpreq == HTTPREQ_POST_FORM))
+    ; /* do nothing */
+  else {
+    if(data->set.ioctl) {
+      curlioerr err;
+
+      err = data->set.ioctl(data, CURLIOCMD_RESTARTREAD,
+                            data->set.ioctl_client);
+      infof(data, "the ioctl callback returned %d\n", (int)err);
+
+      if(err) {
+        /* FIXME: convert to a human readable error message */
+        failf(data, "ioctl callback returned error %d\n", (int)err);
+        return CURLE_SEND_FAIL_REWIND;
+      }
+    }
+    else {
+      /* If no CURLOPT_READFUNCTION is used, we know that we operate on a
+         given FILE * stream and we can actually attempt to rewind that
+         ourself with fseek() */
+      if(data->set.fread == (curl_read_callback)fread) {
+        if(-1 != fseek(data->set.in, 0, SEEK_SET))
+          /* successful rewind */
+          return CURLE_OK;
+      }
+
+      /* no callback set or failure aboe, makes us fail at once */
+      failf(data, "necessary data rewind wasn't possible\n");
+      return CURLE_SEND_FAIL_REWIND;
+    }
+  }
+  return CURLE_OK;
+}
+
 
 /*
  * Curl_readwrite() is the low-level function to be called when data is to
@@ -1163,6 +1212,12 @@ CURLcode Curl_readwrite(struct connectdata *conn,
             /* done */
             k->keepon &= ~KEEP_WRITE; /* we're done writing */
             writedone = TRUE;
+
+            if(conn->bits.rewindaftersend) {
+              result = Curl_readrewind(conn);
+              if(result)
+                return result;
+            }
             break;
           }