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Fix multiple vulnerabilities in the resolver

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This fixes some vulnerabilities in the resolver that make spoofing DNS
queries somewhat trivial due to the code failing to randomize xid, as
well as match the reply xid with the query, and the origin of the packet:

 - xid of the query was fixed at zero
 - xid from the reply was never checked
 - source address of the reply was never checked

This means anyone can flood the host with a fake reply with xid 0,
guessing the source port is trivial as it's less than 16bits (2^16 -
1024), which would cause odin to resolve a hostname to whatever an
attacker wanted.

While here also plug in two memory leaks.

Since this is CVE material, I've contacted @kelimion before hand which
instructed to put it in a PR.

There are also more bugs as the code conflates answer section,
authority section and aditional section into one, while in reality
only the anwer section should be taken into consideration.
This commit is contained in:
Christiano Haesbaert
2025-02-23 00:48:43 +01:00
parent 940da61869
commit 42d7e7a402
1 changed files with 21 additions and 9 deletions
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30
core/net/dns.odin
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@@ -7,10 +7,11 @@ package net
*/
/*
Copyright 2022 Tetralux <tetraluxonpc@gmail.com>
Copyright 2022 Colin Davidson <colrdavidson@gmail.com>
Copyright 2022 Jeroen van Rijn <nom@duclavier.com>.
Copyright 2024 Feoramund <rune@swevencraft.org>.
Copyright 2022 Tetralux <tetraluxonpc@gmail.com>
Copyright 2022 Colin Davidson <colrdavidson@gmail.com>
Copyright 2022 Jeroen van Rijn <nom@duclavier.com>.
Copyright 2024 Feoramund <rune@swevencraft.org>.
Copyright 2025 Christiano Haesbaert <haesbaert@haesbaert.org>.
Made available under Odin's BSD-3 license.
List of contributors:
@@ -18,12 +19,14 @@ package net
Colin Davidson: Linux platform code, OSX platform code, Odin-native DNS resolver
Jeroen van Rijn: Cross platform unification, code style, documentation
Feoramund: FreeBSD platform code
Haesbaert: Security fixes
*/
import "core:mem"
import "core:strings"
import "core:time"
import "core:os"
import "core:math/rand"
/*
Default configuration for DNS resolution.
*/
@@ -227,7 +230,7 @@ get_dns_records_from_nameservers :: proc(hostname: string, type: DNS_Record_Type
}
hdr := DNS_Header{
id = 0,
id = u16be(rand.uint32()),
is_response = false,
opcode = 0,
is_authoritative = false,
@@ -272,17 +275,23 @@ get_dns_records_from_nameservers :: proc(hostname: string, type: DNS_Record_Type
return nil, .Connection_Error
}
recv_sz, _ := recv_udp(conn, dns_response_buf[:]) or_continue
recv_sz, src := recv_udp(conn, dns_response_buf[:]) or_continue
if recv_sz == 0 {
continue
}
if src != name_server {
continue
}
dns_response = dns_response_buf[:recv_sz]
rsp, _ok := parse_response(dns_response, type)
rsp, xid, _ok := parse_response(dns_response, type)
if !_ok {
return nil, .Server_Error
}
if id != xid {
continue
}
if len(rsp) == 0 {
continue
@@ -803,7 +812,7 @@ parse_record :: proc(packet: []u8, cur_off: ^int, filter: DNS_Record_Type = nil)
- Data[]
*/
parse_response :: proc(response: []u8, filter: DNS_Record_Type = nil, allocator := context.allocator) -> (records: []DNS_Record, ok: bool) {
parse_response :: proc(response: []u8, filter: DNS_Record_Type = nil, allocator := context.allocator) -> (records: []DNS_Record, xid: u16be, ok: bool) {
context.allocator = allocator
HEADER_SIZE_BYTES :: 12
@@ -816,11 +825,13 @@ parse_response :: proc(response: []u8, filter: DNS_Record_Type = nil, allocator
dns_hdr_chunks := mem.slice_data_cast([]u16be, response[:HEADER_SIZE_BYTES])
hdr := unpack_dns_header(dns_hdr_chunks[0], dns_hdr_chunks[1])
if !hdr.is_response {
delete(_records)
return
}
question_count := int(dns_hdr_chunks[2])
if question_count != 1 {
delete(_records)
return
}
answer_count := int(dns_hdr_chunks[3])
@@ -872,6 +883,7 @@ parse_response :: proc(response: []u8, filter: DNS_Record_Type = nil, allocator
append(&_records, rec)
}
}
xid = hdr.id
return _records[:], true
return _records[:], xid, true
}