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From 239f8d93866605b05f4e6b551f4327dc7fcb922b Mon Sep 17 00:00:00 2001
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From: Viktor Szakats <commit@vsz.me>
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Date: Tue, 23 Feb 2021 14:54:46 +0100
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Subject: [PATCH 1/2] transfer: strip credentials from the auto-referer header
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 field
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Added test 2081 to verify.
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CVE-2021-22876
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Bug: https://curl.se/docs/CVE-2021-22876.html
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Upstream-commit: 7214288898f5625a6cc196e22a74232eada7861c
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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 lib/transfer.c | 25 +++++++++++++++++++++++--
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 1 file changed, 23 insertions(+), 2 deletions(-)
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diff --git a/lib/transfer.c b/lib/transfer.c
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index ecd1063..263b178 100644
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--- a/lib/transfer.c
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+++ b/lib/transfer.c
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@@ -1473,6 +1473,7 @@ CURLcode Curl_follow(struct Curl_easy *data,
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   /* Location: redirect */
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   bool disallowport = FALSE;
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   bool reachedmax = FALSE;
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+  CURLUcode uc;
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   if(type == FOLLOW_REDIR) {
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     if((data->set.maxredirs != -1) &&
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@@ -1488,6 +1489,9 @@ CURLcode Curl_follow(struct Curl_easy *data,
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       data->set.followlocation++; /* count location-followers */
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       if(data->set.http_auto_referer) {
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+        CURLU *u;
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+        char *referer;
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+
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         /* We are asked to automatically set the previous URL as the referer
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            when we get the next URL. We pick the ->url field, which may or may
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            not be 100% correct */
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@@ -1497,9 +1501,26 @@ CURLcode Curl_follow(struct Curl_easy *data,
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           data->change.referer_alloc = FALSE;
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         }
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-        data->change.referer = strdup(data->change.url);
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-        if(!data->change.referer)
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+        /* Make a copy of the URL without crenditals and fragment */
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+        u = curl_url();
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+        if(!u)
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+          return CURLE_OUT_OF_MEMORY;
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+
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+        uc = curl_url_set(u, CURLUPART_URL, data->change.url, 0);
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+        if(!uc)
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+          uc = curl_url_set(u, CURLUPART_FRAGMENT, NULL, 0);
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+        if(!uc)
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+          uc = curl_url_set(u, CURLUPART_USER, NULL, 0);
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+        if(!uc)
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+          uc = curl_url_set(u, CURLUPART_PASSWORD, NULL, 0);
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+        if(!uc)
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+          uc = curl_url_get(u, CURLUPART_URL, &referer, 0);
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+
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+        curl_url_cleanup(u);
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+
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+        if(uc || referer == NULL)
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           return CURLE_OUT_OF_MEMORY;
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+        data->change.referer = referer;
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         data->change.referer_alloc = TRUE; /* yes, free this later */
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       }
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     }
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-- 
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2.30.2
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From f7d1d478b87499ce31d6aa3251830b78447ad952 Mon Sep 17 00:00:00 2001
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From: Daniel Stenberg <daniel@haxx.se>
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Date: Mon, 29 Mar 2021 09:32:14 +0200
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Subject: [PATCH 2/2] transfer: clear 'referer' in declaration
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To silence (false positive) compiler warnings about it.
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Follow-up to 7214288898f5625
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Reviewed-by: Marcel Raad
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Closes #6810
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Upstream-commit: 6bb028dbda6cbfe83f66de773544f71e4813160f
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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 lib/transfer.c | 4 ++--
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 1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/lib/transfer.c b/lib/transfer.c
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index 263b178..ad5a7ba 100644
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--- a/lib/transfer.c
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+++ b/lib/transfer.c
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@@ -1490,7 +1490,7 @@ CURLcode Curl_follow(struct Curl_easy *data,
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       if(data->set.http_auto_referer) {
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         CURLU *u;
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-        char *referer;
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+        char *referer = NULL;
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         /* We are asked to automatically set the previous URL as the referer
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            when we get the next URL. We pick the ->url field, which may or may
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@@ -1518,7 +1518,7 @@ CURLcode Curl_follow(struct Curl_easy *data,
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         curl_url_cleanup(u);
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-        if(uc || referer == NULL)
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+        if(uc || !referer)
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           return CURLE_OUT_OF_MEMORY;
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         data->change.referer = referer;
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         data->change.referer_alloc = TRUE; /* yes, free this later */
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-- 
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2.30.2
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