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