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From a83dae404feac517695c23ff43ce1e116e2bfbe0 Mon Sep 17 00:00:00 2001
From: Michael Catanzaro <mcatanzaro@gnome.org>
Date: Wed, 9 Sep 2020 11:12:02 -0500
Subject: [PATCH] Rewrite url::recvline to be nonrecursive
This function processes network input. It's semi-trusted, because the
PAC ought to be trusted. But we still shouldn't allow it to control how
far we recurse. A malicious PAC can cause us to overflow the stack by
sending a sufficiently-long line without any '\n' character.
Also, this function failed to properly handle EINTR, so let's fix that
too, for good measure.
Fixes #134
---
libproxy/url.cpp | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)
diff --git a/libproxy/url.cpp b/libproxy/url.cpp
index ee776b2..68d69cd 100644
--- a/libproxy/url.cpp
+++ b/libproxy/url.cpp
@@ -388,16 +388,24 @@ string url::to_string() const {
return m_orig;
}
-static inline string recvline(int fd) {
- // Read a character.
- // If we don't get a character, return empty string.
- // If we are at the end of the line, return empty string.
- char c = '\0';
-
- if (recv(fd, &c, 1, 0) != 1 || c == '\n')
- return "";
-
- return string(1, c) + recvline(fd);
+static string recvline(int fd) {
+ string line;
+ int ret;
+
+ // Reserve arbitrary amount of space to avoid small memory reallocations.
+ line.reserve(128);
+
+ do {
+ char c;
+ ret = recv(fd, &c, 1, 0);
+ if (ret == 1) {
+ if (c == '\n')
+ return line;
+ line += c;
+ }
+ } while (ret == 1 || (ret == -1 && errno == EINTR));
+
+ return line;
}
char* url::get_pac() {
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