Mirrors/CyberChef
2
0
Fork 0
mirror of https://github.com/gchq/CyberChef synced 2025-01-26 03:05:06 +00:00
Code Issues Projects Releases Packages Wiki Activity

Add 'Wrap Input in SEQUENCE' to Parse ASN.1 hex string

Browse source 
This will parse extra tags concatenated to the first tag.
This commit is contained in:
Mark Jansen 2024-08-23 02:14:08 +02:00
parent d635cca210
commit 7cf9ce52b7
No known key found for this signature in database
GPG key ID: B39240EE84BEAE8B
1 changed files with 34 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

36
src/core/operations/ParseASN1HexString.mjs
View file

@ -34,6 +34,12 @@ class ParseASN1HexString extends Operation {
"name": "Truncate octet strings longer than",
"type": "number",
"value": 32
},
{
"name": "Wrap Input in SEQUENCE",
"type": "boolean",
"value": false,
"hint": "Use this when there is extra data that needs to be decoded"
}
];
}
@ -44,8 +50,34 @@ class ParseASN1HexString extends Operation {
* @returns {string}
*/
run(input, args) {
const [index, truncateLen] = args;
return r.ASN1HEX.dump(input.replace(/\s/g, "").toLowerCase(), {
const [index, truncateLen, addSequence] = args;
let hex = input.replace(/\s/g, "").toLowerCase();
if (addSequence) {
let sequence = "30";
let len = hex.length / 2;
if (len <= 127) {
// We can use the short form
sequence += len.toString(16).padStart(2, "0");
} else {
let bytes = 0;
let encoded = "";
// Calculate the number of bytes needed to encode the length
while (len > 0) {
bytes++;
// While we are at it, also build up the length
encoded = (len & 0xff).toString(16).padStart(2, "0") + encoded;
len >>= 8;
}
// encode the number of bytes needed for the length
sequence += (bytes | 0x80).toString(16).padStart(2, "0");
// add the encoded length
sequence += encoded;
}
// Add the sequence + length in front of the original input
hex = sequence + hex;
}
return r.ASN1HEX.dump(hex, {
"ommit_long_octet": truncateLen
}, index);
}