From 1ab8d6ac1861e9405ae34af3deb681020c03e82d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 8 Apr 2020 15:18:41 +0200
Subject: [PATCH] Downloader: Only write data to the sink on a 200 response

Hopefully fixes #3278.
---
 src/libstore/download.cc | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index af69699a866..bc875f65348 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -83,8 +83,15 @@ struct CurlDownloader : public Downloader
             , callback(std::move(callback))
             , finalSink([this](const unsigned char * data, size_t len) {
                 if (this->request.dataCallback) {
-                    writtenToSink += len;
-                    this->request.dataCallback((char *) data, len);
+                    long httpStatus = 0;
+                    curl_easy_getinfo(req, CURLINFO_RESPONSE_CODE, &httpStatus);
+
+                    /* Only write data to the sink if this is a
+                       successful response. */
+                    if (httpStatus == 0 || httpStatus == 200 || httpStatus == 201 || httpStatus == 206) {
+                        writtenToSink += len;
+                        this->request.dataCallback((char *) data, len);
+                    }
                 } else
                     this->result.data->append((char *) data, len);
               })