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BIT-1156: Fix parsing of DNS TXT RRs w/ multiple character-strings.

Browse source 
The "dns_TXT_reply" event now uses a "vector of strings" as the final
parameter instead of just a "string" in order to support DNS TXT
resource records that contain multiple character-strings.

The format in which the TXT answers are logged by default is now changed
to be a list of strings of the form `fmt("TXT %d %s", |str|, str)`, one
for each character-string in the RR and delimited by a space (' ')
character.
This commit is contained in:
Jon Siwek 2014-04-24 16:20:01 -05:00
parent b9e956176e
commit de0ce6deed
4 changed files with 62 additions and 27 deletions
Download patch file Download diff file Expand all files Collapse all files

14
scripts/base/protocols/dns/main.bro
View file

@ -382,9 +382,19 @@ event dns_A_reply(c: connection, msg: dns_msg, ans: dns_answer, a: addr) &priori
hook DNS::do_reply(c, msg, ans, fmt("%s", a));
}
event dns_TXT_reply(c: connection, msg: dns_msg, ans: dns_answer, str: string) &priority=5
event dns_TXT_reply(c: connection, msg: dns_msg, ans: dns_answer, strs: string_vec) &priority=5
{
hook DNS::do_reply(c, msg, ans, str);
local txt_strings: string = "";
for ( i in strs )
{
if ( i > 0 )
txt_strings += " ";
txt_strings += fmt("TXT %d %s", |strs[i]|, strs[i]);
}
hook DNS::do_reply(c, msg, ans, txt_strings);
}
event dns_AAAA_reply(c: connection, msg: dns_msg, ans: dns_answer, a: addr) &priority=5

51
src/analyzer/protocol/dns/DNS.cc
View file

@ -835,34 +835,59 @@ int DNS_Interpreter::ParseRR_HINFO(DNS_MsgInfo* msg,
return 1;
}
static StringVal* extract_char_string(analyzer::Analyzer* analyzer,
const u_char*& data, int& len, int& rdlen)
{
if ( rdlen <= 0 )
return 0;
uint8 str_size = data[0];
--rdlen;
--len;
++data;
if ( str_size > rdlen )
{
analyzer->Weird("DNS_TXT_char_str_past_rdlen");
return 0;
}
StringVal* rval = new StringVal(str_size,
reinterpret_cast<const char*>(data));
rdlen -= str_size;
len -= str_size;
data += str_size;
return rval;
}
int DNS_Interpreter::ParseRR_TXT(DNS_MsgInfo* msg,
const u_char*& data, int& len, int rdlength,
const u_char* msg_start)
{
int name_len = data[0];
char* name = new char[name_len];
memcpy(name, data+1, name_len);
if ( ! dns_TXT_reply || msg->skip_event )
{
data += rdlength;
len -= rdlength;
return 1;
}
VectorVal* char_strings = new VectorVal(string_vec);
StringVal* char_string;
while ( (char_string = extract_char_string(analyzer, data, len, rdlength)) )
char_strings->Assign(char_strings->Size(), char_string);
if ( dns_TXT_reply && ! msg->skip_event )
{
val_list* vl = new val_list;
vl->append(analyzer->BuildConnVal());
vl->append(msg->BuildHdrVal());
vl->append(msg->BuildAnswerVal());
vl->append(new StringVal(name_len, name));
vl->append(char_strings);
analyzer->ConnectionEvent(dns_TXT_reply, vl);
}
delete [] name;
return 1;
return rdlength == 0;
}
void DNS_Interpreter::SendReplyOrRejectEvent(DNS_MsgInfo* msg,

2
src/analyzer/protocol/dns/events.bif
View file

@ -376,7 +376,7 @@ event dns_MX_reply%(c: connection, msg: dns_msg, ans: dns_answer, name: string,
## dns_mapping_unverified dns_mapping_valid dns_message dns_query_reply
## dns_rejected dns_request non_dns_request dns_max_queries dns_session_timeout
## dns_skip_addl dns_skip_all_addl dns_skip_all_auth dns_skip_auth
event dns_TXT_reply%(c: connection, msg: dns_msg, ans: dns_answer, str: string%);
event dns_TXT_reply%(c: connection, msg: dns_msg, ans: dns_answer, strs: string_vec%);
## Generated for DNS replies of type *SRV*. For replies with multiple answers,
## an individual event of the corresponding type is raised for each.

8
testing/btest/Baseline/core.ipv6-frag/dns.log
View file

@ -3,10 +3,10 @@
#empty_field (empty)
#unset_field -
#path dns
#open 2013-08-26-19-02-10
#open 2014-04-24-20-25-19
#fields ts uid id.orig_h id.orig_p id.resp_h id.resp_p proto trans_id query qclass qclass_name qtype qtype_name rcode rcode_name AA TC RD RA Z answers TTLs rejected
#types time string addr port addr port enum count string count string count string count string bool bool bool bool count vector[string] vector[interval] bool
1331084278.438444 CXWv6p3arKYeMETxOg 2001:470:1f11:81f:d138:5f55:6d4:1fe2 51850 2607:f740:b::f93 53 udp 3903 txtpadding_323.n1.netalyzr.icsi.berkeley.edu 1 C_INTERNET 16 TXT 0 NOERROR T F T F 0 This TXT record should be ignored 1.000000 F
1331084293.592245 CjhGID4nQcgTWjvg4c 2001:470:1f11:81f:d138:5f55:6d4:1fe2 51851 2607:f740:b::f93 53 udp 40849 txtpadding_3230.n1.netalyzr.icsi.berkeley.edu 1 C_INTERNET 16 TXT 0 NOERROR T F T F 0 This TXT record should be ignored 1.000000 F
1331084278.438444 CXWv6p3arKYeMETxOg 2001:470:1f11:81f:d138:5f55:6d4:1fe2 51850 2607:f740:b::f93 53 udp 3903 txtpadding_323.n1.netalyzr.icsi.berkeley.edu 1 C_INTERNET 16 TXT 0 NOERROR T F T F 0 TXT 33 This TXT record should be ignored TXT 21 As it is just padding TXT 136 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 1.000000 F
1331084293.592245 CjhGID4nQcgTWjvg4c 2001:470:1f11:81f:d138:5f55:6d4:1fe2 51851 2607:f740:b::f93 53 udp 40849 txtpadding_3230.n1.netalyzr.icsi.berkeley.edu 1 C_INTERNET 16 TXT 0 NOERROR T F T F 0 TXT 33 This TXT record should be ignored TXT 21 As it is just padding TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 189 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX TXT 192 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 1.000000 F
1331084298.593081 CjhGID4nQcgTWjvg4c 2001:470:1f11:81f:d138:5f55:6d4:1fe2 51851 2607:f740:b::f93 53 udp 40849 txtpadding_3230.n1.netalyzr.icsi.berkeley.edu 1 C_INTERNET 16 TXT - - F F T F 0 - - F
#close 2013-08-26-19-02-10
#close 2014-04-24-20-25-20