1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
From a2dc11b37fd71f785c342c40549f54edfdd1a6f8 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Thu, 11 May 2023 21:40:15 -0700
Subject: [PATCH] QDnsLookup/Unix: make sure we don't overflow the buffer
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit
The DNS Records are variable length and encode their size in 16 bits
before the Record Data (RDATA). Ensure that both the RDATA and the
Record header fields before it fall inside the buffer we have.
Additionally reject any replies containing more than one query records.
[ChangeLog][QtNetwork][QDnsLookup] Fixed a bug that could cause a buffer
overflow in Unix systems while parsing corrupt, malicious, or truncated
replies.
Pick-to: 5.15 6.2 6.5.1
Change-Id: I3e3bfef633af4130a03afffd175e4b9547654b95
Reviewed-by: MÃ¥rten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Jani Heikkinen <jani.heikkinen@qt.io>
(cherry picked from commit 7dba2c87619d558a61a30eb30cc1d9c3fe6df94c)
Reviewed-by: Daniel Smith <Daniel.Smith@qt.io>
---
src/network/kernel/qdnslookup_unix.cpp | 31 +++++++++++++++++++++++++------
1 file changed, 25 insertions(+), 6 deletions(-)
diff --git a/src/network/kernel/qdnslookup_unix.cpp b/src/network/kernel/qdnslookup_unix.cpp
index 8db79028f775..ad7bb51f67a5 100644
--- a/src/network/kernel/qdnslookup_unix.cpp
+++ b/src/network/kernel/qdnslookup_unix.cpp
@@ -193,7 +193,6 @@ void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestN
// responseLength in case of error, we still can extract the
// exact error code from the response.
HEADER *header = (HEADER*)response;
- const int answerCount = ntohs(header->ancount);
switch (header->rcode) {
case NOERROR:
break;
@@ -227,18 +226,31 @@ void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestN
return;
}
- // Skip the query host, type (2 bytes) and class (2 bytes).
char host[PACKETSZ], answer[PACKETSZ];
unsigned char *p = response + sizeof(HEADER);
- int status = local_dn_expand(response, response + responseLength, p, host, sizeof(host));
- if (status < 0) {
+ int status;
+
+ if (ntohs(header->qdcount) == 1) {
+ // Skip the query host, type (2 bytes) and class (2 bytes).
+ status = local_dn_expand(response, response + responseLength, p, host, sizeof(host));
+ if (status < 0) {
+ reply->error = QDnsLookup::InvalidReplyError;
+ reply->errorString = tr("Could not expand domain name");
+ return;
+ }
+ if ((p - response) + status + 4 >= responseLength)
+ header->qdcount = 0xffff; // invalid reply below
+ else
+ p += status + 4;
+ }
+ if (ntohs(header->qdcount) > 1) {
reply->error = QDnsLookup::InvalidReplyError;
- reply->errorString = tr("Could not expand domain name");
+ reply->errorString = tr("Invalid reply received");
return;
}
- p += status + 4;
// Extract results.
+ const int answerCount = ntohs(header->ancount);
int answerIndex = 0;
while ((p < response + responseLength) && (answerIndex < answerCount)) {
status = local_dn_expand(response, response + responseLength, p, host, sizeof(host));
@@ -250,6 +262,11 @@ void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestN
const QString name = QUrl::fromAce(host);
p += status;
+
+ if ((p - response) + 10 > responseLength) {
+ // probably just a truncated reply, return what we have
+ return;
+ }
const quint16 type = (p[0] << 8) | p[1];
p += 2; // RR type
p += 2; // RR class
@@ -257,6 +274,8 @@ void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestN
p += 4;
const quint16 size = (p[0] << 8) | p[1];
p += 2;
+ if ((p - response) + size > responseLength)
+ return; // truncated
if (type == QDnsLookup::A) {
if (size != 4) {
--
2.16.3
|
