--- /dev/null
+From 4411b523545b22022b4be7d0cac25aa170ae1d3e Mon Sep 17 00:00:00 2001
+From: Fei Li <lifeibiren@gmail.com>
+Date: Fri, 17 Jul 2020 02:18:37 +0800
+Subject: [PATCH] Fix buffer overflow when PAC is enabled
+
+The bug was found on Windows 10 (MINGW64) when PAC is enabled. It turned
+out to be the large PAC file (more than 102400 bytes) returned by a
+local proxy program with no content-length present.
+
+Upstream-Status: Backport [https://github.com/libproxy/libproxy/commit/6d342b50366a048d3d543952e2be271b5742c5f8]
+CVE: CVE-2020-26154
+Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com>
+
+---
+ libproxy/url.cpp | 44 +++++++++++++++++++++++++++++++-------------
+ 1 file changed, 31 insertions(+), 13 deletions(-)
+
+diff --git a/libproxy/url.cpp b/libproxy/url.cpp
+index ee776b2..8684086 100644
+--- a/libproxy/url.cpp
++++ b/libproxy/url.cpp
+@@ -54,7 +54,7 @@ using namespace std;
+ #define PAC_MIME_TYPE_FB "text/plain"
+
+ // This is the maximum pac size (to avoid memory attacks)
+-#define PAC_MAX_SIZE 102400
++#define PAC_MAX_SIZE 0x800000
+ // This is the default block size to use when receiving via HTTP
+ #define PAC_HTTP_BLOCK_SIZE 512
+
+@@ -478,15 +478,13 @@ char* url::get_pac() {
+ }
+
+ // Get content
+- unsigned int recvd = 0;
+- buffer = new char[PAC_MAX_SIZE];
+- memset(buffer, 0, PAC_MAX_SIZE);
++ std::vector<char> dynamic_buffer;
+ do {
+ unsigned int chunk_length;
+
+ if (chunked) {
+ // Discard the empty line if we received a previous chunk
+- if (recvd > 0) recvline(sock);
++ if (!dynamic_buffer.empty()) recvline(sock);
+
+ // Get the chunk-length line as an integer
+ if (sscanf(recvline(sock).c_str(), "%x", &chunk_length) != 1 || chunk_length == 0) break;
+@@ -498,21 +496,41 @@ char* url::get_pac() {
+
+ if (content_length >= PAC_MAX_SIZE) break;
+
+- while (content_length == 0 || recvd != content_length) {
+- int r = recv(sock, buffer + recvd,
+- content_length == 0 ? PAC_HTTP_BLOCK_SIZE
+- : content_length - recvd, 0);
++ while (content_length == 0 || dynamic_buffer.size() != content_length) {
++ // Calculate length to recv
++ unsigned int length_to_read = PAC_HTTP_BLOCK_SIZE;
++ if (content_length > 0)
++ length_to_read = content_length - dynamic_buffer.size();
++
++ // Prepare buffer
++ dynamic_buffer.resize(dynamic_buffer.size() + length_to_read);
++
++ int r = recv(sock, dynamic_buffer.data() + dynamic_buffer.size() - length_to_read, length_to_read, 0);
++
++ // Shrink buffer to fit
++ if (r >= 0)
++ dynamic_buffer.resize(dynamic_buffer.size() - length_to_read + r);
++
++ // PAC size too large, discard
++ if (dynamic_buffer.size() >= PAC_MAX_SIZE) {
++ chunked = false;
++ dynamic_buffer.clear();
++ break;
++ }
++
+ if (r <= 0) {
+ chunked = false;
+ break;
+ }
+- recvd += r;
+ }
+ } while (chunked);
+
+- if (content_length != 0 && string(buffer).size() != content_length) {
+- delete[] buffer;
+- buffer = NULL;
++ if (content_length == 0 || content_length == dynamic_buffer.size()) {
++ buffer = new char[dynamic_buffer.size() + 1];
++ if (!dynamic_buffer.empty()) {
++ memcpy(buffer, dynamic_buffer.data(), dynamic_buffer.size());
++ }
++ buffer[dynamic_buffer.size()] = '\0';
+ }
+ }
+
