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Protodetect enip dns 4388 v7 #6185

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Protodetect enip dns 4388 v7 #6185

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c393401
enip: improve probing parser
catenacyber Mar 9, 2021
344a6c3
dns: improve probing parser
catenacyber Mar 9, 2021
f355941
nfs: improve probing parser
catenacyber Mar 16, 2021
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47 changes: 37 additions & 10 deletions rust/src/dns/dns.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -659,23 +659,50 @@ impl DNSState {
}
}

fn probe_header_validity(header : DNSHeader, rlen: usize) -> (bool, bool, bool) {
let opcode = ((header.flags >> 11) & 0xf) as u8;
if opcode >= 7 {
//unassigned opcode
return (false, false, false);
}
if header.additional_rr as usize
+ header.answer_rr as usize
+ header.authority_rr as usize
+ header.questions as usize
> rlen
{
//not enough data for additional records
return (false, false, false);
}
Comment on lines +668 to +676
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As these are counts not sizes, its not accurate, but also won't false positive. Should the size of the header be calculated in as well? If sizeof(header) + addtional_rr +answer_rr > rlen... Might be a bit more accurate. I think we could also assume a minumum of 2 bytes per expected record being the CLASS is a u16.

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Indeed, these are counts, not sizes.
And I do not count the header size.
But as each of these has at least one byte, we can do this test to exclude some cases

So, should I include the header size in this sum ?

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I think so. Just to confirm, rlen is the size of the record. In TCP this would be the first 2 bytes, in UDP its the payload size.

So a test to make sure its greater than or equal to:

sizeof(header) + (additional_rr * 2) + (answer_rr * 2) + (authority_rr * 2) + (questions * 2)

should be safe and accurate, right?

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I think so. Just to confirm, rlen is the size of the record. In TCP this would be the first 2 bytes, in UDP its the payload size.

Exactly, you can check the callers do it right

So a test to make sure its greater than or equal to:

sizeof(header) + (additional_rr * 2) + (answer_rr * 2) + (authority_rr * 2) + (questions * 2)

should be safe and accurate, right?

Ok, will do this

let is_request = header.flags & 0x8000 == 0;
return (true, is_request, false);
}

/// Probe input to see if it looks like DNS.
fn probe(input: &[u8]) -> (bool, bool) {
match parser::dns_parse_request(input) {
fn probe(input: &[u8], dlen: usize) -> (bool, bool, bool) {
let i2 = if input.len() <= dlen { input } else { &input[..dlen] };
match parser::dns_parse_request(i2) {
Ok((_, request)) => {
let is_request = request.header.flags & 0x8000 == 0;
return (true, is_request);
return probe_header_validity(request.header, dlen);
},
Err(_) => (false, false),
Err(nom::Err::Incomplete(_)) => {
match parser::dns_parse_header(input) {
Ok((_, header)) => {
return probe_header_validity(header, dlen);
}
Err(nom::Err::Incomplete(_)) => (false, false, true),
Err(_) => (false, false, false),
}
}
Err(_) => (false, false, false),
}
}

/// Probe TCP input to see if it looks like DNS.
pub fn probe_tcp(input: &[u8]) -> (bool, bool, bool) {
match be_u16(input) as IResult<&[u8],_> {
Ok((rem, _)) => {
let r = probe(rem);
return (r.0, r.1, false);
match be_u16(input) as IResult<&[u8],u16> {
Ok((rem, dlen)) => {
return probe(rem, dlen as usize);
},
Err(nom::Err::Incomplete(_)) => {
return (false, false, true);
Expand Down Expand Up @@ -961,7 +988,7 @@ pub extern "C" fn rs_dns_probe(
let slice: &[u8] = unsafe {
std::slice::from_raw_parts(input as *mut u8, len as usize)
};
let (is_dns, is_request) = probe(slice);
let (is_dns, is_request, _) = probe(slice, slice.len());
if is_dns {
let dir = if is_request {
core::STREAM_TOSERVER
Expand Down
2 changes: 1 addition & 1 deletion rust/src/nfs/nfs.rs
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Expand Up @@ -1739,7 +1739,7 @@ pub fn nfs_probe(i: &[u8], direction: u8) -> i8 {
rpc.program == 100003 &&
rpc.procedure <= NFSPROC3_COMMIT
{
return 1;
return rpc_auth_type_known(rpc.creds_flavor);
} else {
return -1;
}
Expand Down
8 changes: 8 additions & 0 deletions rust/src/nfs/types.rs
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Expand Up @@ -177,6 +177,14 @@ pub fn rpc_auth_type_string(auth_type: u32) -> String {
}.to_string()
}

pub fn rpc_auth_type_known(auth_type: u32) -> i8 {
// RPCAUTH_GSS is the maximum
if auth_type <= RPCAUTH_GSS {
return 1;
}
return -1;
}

/* http://www.iana.org/assignments/rpc-authentication-numbers/rpc-authentication-numbers.xhtml */
pub const RPCAUTH_OK: u32 = 0; // success/failed at remote end [RFC5531]
pub const RPCAUTH_BADCRED: u32 = 1; // bad credential (seal broken) [RFC5531]
Expand Down
87 changes: 67 additions & 20 deletions src/app-layer-enip.c
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Expand Up @@ -359,7 +359,7 @@ static AppLayerResult ENIPParse(Flow *f, void *state, AppLayerParserState *pstat
SCReturnStruct(APP_LAYER_OK);
}


#define ENIP_LEN_REGISTER_SESSION 4 // protocol u16, options u16

static uint16_t ENIPProbingParser(Flow *f, uint8_t direction,
const uint8_t *input, uint32_t input_len, uint8_t *rdir)
Expand All @@ -371,43 +371,90 @@ static uint16_t ENIPProbingParser(Flow *f, uint8_t direction,
return ALPROTO_UNKNOWN;
}
uint16_t cmd;
uint16_t enip_len;
uint32_t status;
int ret = ByteExtractUint16(&cmd, BYTE_LITTLE_ENDIAN, sizeof(uint16_t),
(const uint8_t *) (input));
uint32_t option;
uint16_t nbitems;

int ret = ByteExtractUint16(
&enip_len, BYTE_LITTLE_ENDIAN, sizeof(uint16_t), (const uint8_t *)(input + 2));
if (ret < 0) {
return ALPROTO_FAILED;
}
if (enip_len < sizeof(ENIPEncapHdr)) {
return ALPROTO_FAILED;
}
ret = ByteExtractUint32(
&status, BYTE_LITTLE_ENDIAN, sizeof(uint32_t), (const uint8_t *)(input + 8));
if (ret < 0) {
return ALPROTO_FAILED;
}
switch (status) {
case SUCCESS:
case INVALID_CMD:
case NO_RESOURCES:
case INCORRECT_DATA:
case INVALID_SESSION:
case INVALID_LENGTH:
case UNSUPPORTED_PROT_REV:
case ENCAP_HEADER_ERROR:
break;
default:
return ALPROTO_FAILED;
}
ret = ByteExtractUint16(&cmd, BYTE_LITTLE_ENDIAN, sizeof(uint16_t), (const uint8_t *)(input));
if(ret < 0) {
return ALPROTO_FAILED;
}
ret = ByteExtractUint32(
&option, BYTE_LITTLE_ENDIAN, sizeof(uint32_t), (const uint8_t *)(input + 20));
if (ret < 0) {
return ALPROTO_FAILED;
}

//ok for all the known commands
switch(cmd) {
case NOP:
case LIST_SERVICES:
case LIST_IDENTITY:
case LIST_INTERFACES:
if (option != 0) {
return ALPROTO_FAILED;
}
break;
case REGISTER_SESSION:
if (enip_len != ENIP_LEN_REGISTER_SESSION) {
return ALPROTO_FAILED;
}
break;
case UNREGISTER_SESSION:
if (enip_len != ENIP_LEN_REGISTER_SESSION && enip_len != 0) {
// 0 for request and 4 for response
return ALPROTO_FAILED;
}
break;
case LIST_SERVICES:
case LIST_IDENTITY:
case SEND_RR_DATA:
case SEND_UNIT_DATA:
case INDICATE_STATUS:
case CANCEL:
ret = ByteExtractUint32(&status, BYTE_LITTLE_ENDIAN,
sizeof(uint32_t),
(const uint8_t *) (input + 8));
break;
case LIST_INTERFACES:
if (input_len < sizeof(ENIPEncapHdr) + 2) {
SCLogDebug("length too small to be a ENIP LIST_INTERFACES");
return ALPROTO_UNKNOWN;
}
ret = ByteExtractUint16(
&nbitems, BYTE_LITTLE_ENDIAN, sizeof(uint16_t), (const uint8_t *)(input));
if(ret < 0) {
return ALPROTO_FAILED;
}
switch(status) {
case SUCCESS:
case INVALID_CMD:
case NO_RESOURCES:
case INCORRECT_DATA:
case INVALID_SESSION:
case INVALID_LENGTH:
case UNSUPPORTED_PROT_REV:
case ENCAP_HEADER_ERROR:
return ALPROTO_ENIP;
if (enip_len < sizeof(ENIPEncapHdr) + 2 * (size_t)nbitems) {
return ALPROTO_FAILED;
}
break;
default:
return ALPROTO_FAILED;
}
return ALPROTO_FAILED;
return ALPROTO_ENIP;
}

/**
Expand Down