@ -2,6 +2,7 @@ use crate::dnscrypt_certs::*;
use crate ::errors ::* ;
use byteorder ::{ BigEndian , ByteOrder , WriteBytesExt } ;
use std ::net ::IpAddr ;
use std ::sync ::Arc ;
pub const DNS_MAX_HOSTNAME_SIZE : usize = 256 ;
@ -104,6 +105,12 @@ fn arcount_inc(packet: &mut [u8]) -> Result<(), Error> {
Ok ( ( ) )
}
#[ inline ]
fn arcount_clear ( packet : & mut [ u8 ] ) -> Result < ( ) , Error > {
BigEndian ::write_u16 ( & mut packet [ 10 .. ] , 0 ) ;
Ok ( ( ) )
}
#[ inline ]
pub fn an_ns_ar_count_clear ( packet : & mut [ u8 ] ) {
packet [ 6 .. 12 ] . iter_mut ( ) . for_each ( | x | * x = 0 ) ;
@ -312,13 +319,13 @@ fn traverse_rrs<F: FnMut(usize) -> Result<(), Error>>(
for _ in 0 .. rrcount {
offset = skip_name ( packet , offset ) ? ;
ensure ! ( packet_len - offset > = 10 , "Short packet" ) ;
cb ( offset ) ? ;
let rdlen = BigEndian ::read_u16 ( & packet [ offset + 8 .. ] ) as usize ;
offset + = 10 ;
ensure ! (
packet_len - offset > = rdlen ,
packet_len - offset > = 10 + rdlen ,
"Record length would exceed packet length"
) ;
cb ( offset ) ? ;
offset + = 10 ;
offset + = rdlen ;
}
Ok ( offset )
@ -334,13 +341,13 @@ fn traverse_rrs_mut<F: FnMut(&mut [u8], usize) -> Result<(), Error>>(
for _ in 0 .. rrcount {
offset = skip_name ( packet , offset ) ? ;
ensure ! ( packet_len - offset > = 10 , "Short packet" ) ;
cb ( packet , offset ) ? ;
let rdlen = BigEndian ::read_u16 ( & packet [ offset + 8 .. ] ) as usize ;
offset + = 10 ;
ensure ! (
packet_len - offset > = rdlen ,
packet_len - offset > = 10 + rdlen ,
"Record length would exceed packet length"
) ;
cb ( packet , offset ) ? ;
offset + = 10 ;
offset + = rdlen ;
}
Ok ( offset )
@ -374,6 +381,28 @@ pub fn min_ttl(packet: &[u8], min_ttl: u32, max_ttl: u32, failure_ttl: u32) -> R
Ok ( found_min_ttl )
}
pub fn set_ttl ( packet : & mut [ u8 ] , ttl : u32 ) -> Result < ( ) , Error > {
let packet_len = packet . len ( ) ;
ensure ! ( packet_len > DNS_OFFSET_QUESTION , "Short packet" ) ;
ensure ! ( packet_len < = DNS_MAX_PACKET_SIZE , "Large packet" ) ;
ensure ! ( qdcount ( packet ) = = 1 , "No question" ) ;
let mut offset = skip_name ( packet , DNS_OFFSET_QUESTION ) ? ;
assert! ( offset > DNS_OFFSET_QUESTION ) ;
ensure ! ( packet_len - offset > 4 , "Short packet" ) ;
offset + = 4 ;
let ( ancount , nscount , arcount ) = ( ancount ( packet ) , nscount ( packet ) , arcount ( packet ) ) ;
let rrcount = ancount as usize + nscount as usize + arcount as usize ;
offset = traverse_rrs_mut ( packet , offset , rrcount , | packet , offset | {
let qtype = BigEndian ::read_u16 ( & packet [ offset .. ] ) ;
if qtype ! = DNS_TYPE_OPT {
BigEndian ::write_u32 ( & mut packet [ offset + 4 .. ] , ttl )
}
Ok ( ( ) )
} ) ? ;
ensure ! ( packet_len = = offset , "Garbage after packet" ) ;
Ok ( ( ) )
}
fn add_edns_section ( packet : & mut Vec < u8 > , max_payload_size : u16 ) -> Result < ( ) , Error > {
let opt_rr : [ u8 ; 11 ] = [
0 ,
@ -502,6 +531,73 @@ pub fn qtype_qclass(packet: &[u8]) -> Result<(u16, u16), Error> {
Ok ( ( qtype , qclass ) )
}
fn parse_txt_rrdata < F : FnMut ( & str ) -> Result < ( ) , Error > > (
rrdata : & [ u8 ] ,
mut cb : F ,
) -> Result < ( ) , Error > {
let rrdata_len = rrdata . len ( ) ;
let mut offset = 0 ;
while offset < rrdata_len {
let part_len = rrdata [ offset ] as usize ;
if part_len = = 0 {
break ;
}
ensure ! ( rrdata_len - offset > part_len , "Short TXT RR data" ) ;
offset + = 1 ;
let part_bin = & rrdata [ offset .. offset + part_len ] ;
let part = std ::str ::from_utf8 ( part_bin ) ? ;
cb ( part ) ? ;
offset + = part_len ;
}
Ok ( ( ) )
}
pub fn query_meta ( packet : & mut Vec < u8 > ) -> Result < Option < String > , Error > {
let packet_len = packet . len ( ) ;
ensure ! ( packet_len > DNS_OFFSET_QUESTION , "Short packet" ) ;
ensure ! ( packet_len < = DNS_MAX_PACKET_SIZE , "Large packet" ) ;
ensure ! ( qdcount ( packet ) = = 1 , "No question" ) ;
let mut offset = skip_name ( packet , DNS_OFFSET_QUESTION ) ? ;
assert! ( offset > DNS_OFFSET_QUESTION ) ;
ensure ! ( packet_len - offset > = 4 , "Short packet" ) ;
offset + = 4 ;
let ( ancount , nscount , arcount ) = ( ancount ( packet ) , nscount ( packet ) , arcount ( packet ) ) ;
offset = traverse_rrs (
packet ,
offset ,
ancount as usize + nscount as usize ,
| _offset | Ok ( ( ) ) ,
) ? ;
let mut token = None ;
traverse_rrs ( packet , offset , arcount as _ , | mut offset | {
let qtype = BigEndian ::read_u16 ( & packet [ offset .. ] ) ;
let qclass = BigEndian ::read_u16 ( & packet [ offset + 2 .. ] ) ;
if qtype ! = DNS_TYPE_TXT | | qclass ! = DNS_CLASS_INET {
return Ok ( ( ) ) ;
}
let len = BigEndian ::read_u16 ( & packet [ offset + 8 .. ] ) as usize ;
offset + = 10 ;
ensure ! ( packet_len - offset > = len , "Short packet" ) ;
let rrdata = & packet [ offset .. offset + len ] ;
parse_txt_rrdata ( rrdata , | txt | {
if txt . len ( ) < 7 | | ! txt . starts_with ( "token:" ) {
return Ok ( ( ) ) ;
}
ensure ! ( token . is_none ( ) , "Duplicate token" ) ;
let found_token = & txt [ 6 .. ] ;
let found_token = found_token . to_owned ( ) ;
token = Some ( found_token ) ;
Ok ( ( ) )
} ) ? ;
Ok ( ( ) )
} ) ? ;
if token . is_some ( ) {
arcount_clear ( packet ) ? ;
packet . truncate ( offset ) ;
}
Ok ( token )
}
pub fn serve_nxdomain_response ( client_packet : Vec < u8 > ) -> Result < Vec < u8 > , Error > {
ensure ! ( client_packet . len ( ) > = DNS_HEADER_SIZE , "Short packet" ) ;
ensure ! ( qdcount ( & client_packet ) = = 1 , "No question" ) ;
@ -547,3 +643,37 @@ pub fn serve_blocked_response(client_packet: Vec<u8>) -> Result<Vec<u8>, Error>
packet . extend_from_slice ( hinfo_rdata ) ;
Ok ( packet )
}
pub fn serve_ip_response ( client_packet : Vec < u8 > , ip : IpAddr , ttl : u32 ) -> Result < Vec < u8 > , Error > {
ensure ! ( client_packet . len ( ) > = DNS_HEADER_SIZE , "Short packet" ) ;
ensure ! ( qdcount ( & client_packet ) = = 1 , "No question" ) ;
ensure ! (
! is_response ( & client_packet ) ,
"Question expected, but got a response instead"
) ;
let offset = skip_name ( & client_packet , DNS_HEADER_SIZE ) ? ;
let mut packet = client_packet ;
ensure ! ( packet . len ( ) - offset > = 4 , "Short packet" ) ;
packet . truncate ( offset + 4 ) ;
an_ns_ar_count_clear ( & mut packet ) ;
authoritative_response ( & mut packet ) ;
ancount_inc ( & mut packet ) ? ;
packet . write_u16 ::< BigEndian > ( 0xc000 + DNS_HEADER_SIZE as u16 ) ? ;
match ip {
IpAddr ::V4 ( ip ) = > {
packet . write_u16 ::< BigEndian > ( DNS_TYPE_A ) ? ;
packet . write_u16 ::< BigEndian > ( DNS_CLASS_INET ) ? ;
packet . write_u32 ::< BigEndian > ( ttl ) ? ;
packet . write_u16 ::< BigEndian > ( 4 ) ? ;
packet . extend_from_slice ( & ip . octets ( ) ) ;
}
IpAddr ::V6 ( ip ) = > {
packet . write_u16 ::< BigEndian > ( DNS_TYPE_AAAA ) ? ;
packet . write_u16 ::< BigEndian > ( DNS_CLASS_INET ) ? ;
packet . write_u32 ::< BigEndian > ( ttl ) ? ;
packet . write_u16 ::< BigEndian > ( 16 ) ? ;
packet . extend_from_slice ( & ip . octets ( ) ) ;
}
} ;
Ok ( packet )
}
Frank Denis
4 years ago