From 7214288898f5625a6cc196e22a74232eada7861c Mon Sep 17 00:00:00 2001
From: Viktor Szakats <commit@vsz.me>
Date: Tue, 23 Feb 2021 14:54:46 +0100
Subject: [PATCH] transfer: strip credentials from the auto-referer header
 field

Added test 2081 to verify.

CVE-2021-22876

Bug: https://curl.se/docs/CVE-2021-22876.html

Conflict: remove tests/data/Makefile.inc tests/data/test2081
Reference: https://github.com/curl/curl/commit/7214288898f5625a6cc196e22a74232eada7861c
---
 lib/transfer.c          | 25 ++++++++++++++--
 1 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/lib/transfer.c b/lib/transfer.c
index 1976bc033..a68c021c8 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -1582,6 +1582,9 @@ CURLcode Curl_follow(struct Curl_easy *data,
       data->set.followlocation++; /* count location-followers */
 
       if(data->set.http_auto_referer) {
+        CURLU *u;
+        char *referer;
+
         /* We are asked to automatically set the previous URL as the referer
            when we get the next URL. We pick the ->url field, which may or may
            not be 100% correct */
@@ -1591,9 +1594,27 @@ CURLcode Curl_follow(struct Curl_easy *data,
           data->change.referer_alloc = FALSE;
         }
 
-        data->change.referer = strdup(data->change.url);
-        if(!data->change.referer)
+        /* Make a copy of the URL without crenditals and fragment */
+        u = curl_url();
+        if(!u)
+          return CURLE_OUT_OF_MEMORY;
+
+        uc = curl_url_set(u, CURLUPART_URL, data->change.url, 0);
+        if(!uc)
+          uc = curl_url_set(u, CURLUPART_FRAGMENT, NULL, 0);
+        if(!uc)
+          uc = curl_url_set(u, CURLUPART_USER, NULL, 0);
+        if(!uc)
+          uc = curl_url_set(u, CURLUPART_PASSWORD, NULL, 0);
+        if(!uc)
+          uc = curl_url_get(u, CURLUPART_URL, &referer, 0);
+
+        curl_url_cleanup(u);
+
+        if(uc || referer == NULL)
           return CURLE_OUT_OF_MEMORY;
+
+        data->change.referer = referer;
         data->change.referer_alloc = TRUE; /* yes, free this later */
       }
     }
-- 
2.23.0