Fix PAC buffer overflow (#1883584)

libproxy-0.4.15-fix-pac-buffer-overflow.patch

@@ -0,0 +1,93 @@
+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.
+---
+ 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';
+ 		}
+ 	}
+ 

libproxy.spec

@@ -4,7 +4,7 @@
 
 Name:           libproxy
 Version:        0.4.15
-Release:        25%{?dist}
+Release:        26%{?dist}
 Summary:        A library handling all the details of proxy configuration
 
 License:        LGPLv2+
@@ -29,6 +29,8 @@ Patch6:         libproxy-0.4.15-mozjs68.patch
 Patch7:         libproxy-0.4.15-mozjs-use-after-free.patch
 # https://bugzilla.redhat.com/show_bug.cgi?id=1880350
 Patch8:         libproxy-0.4.15-fix-CVE-2020-25219.patch
+# https://bugzilla.redhat.com/show_bug.cgi?id=1883584
+Patch9:         libproxy-0.4.15-fix-pac-buffer-overflow.patch
 
 BuildRequires:  cmake >= 2.6.0
 BuildRequires:  gcc-c++
@@ -233,6 +235,9 @@ install -Dpm 0644 %{SOURCE1} %{buildroot}/%{_mandir}/man1/proxy.1
 
 
 %changelog
+* Tue Sep 29 2020 David King <amigadave@amigadave.com> - 0.4.15-26
+- Fix PAC buffer overflow (#1883584)
+
 * Fri Sep 18 2020 David King <amigadave@amigadave.com> - 0.4.15-25
 - Fix CVE-2020-25219 (#1880350)