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old-keypairs.js
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v1.2.12: fix EC sig padding issues

This commit is contained in:
AJ ONeal 2019-03-08 19:03:55 -07:00
parent 65db78a3c5
commit 3c84a7e1bd
2 changed files with 22 additions and 16 deletions
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36
keypairs.js
View File

@ -237,7 +237,7 @@ Keypairs.signJws = function (opts) {
.update(protect ? (protected64 + "." + payload64) : payload64)
.sign(pem)
;
if (!opts.jwk || 'RSA' !== opts.jwk.kty) {
if ('EC' === opts.jwk.kty) {
// ECDSA JWT signatures differ from "normal" ECDSA signatures
// https://tools.ietf.org/html/rfc7518#section-3.4
binsig = convertIfEcdsa(binsig);
@ -259,31 +259,37 @@ Keypairs.signJws = function (opts) {
function convertIfEcdsa(binsig) {
// should have asn1 sequence header of 0x30
if (0x30 !== binsig[0]) { return binsig; }
if (0x30 !== binsig[0]) { throw new Error("Impossible EC SHA head marker"); }
var index = 2; // first ecdsa "R" header byte
var len = binsig[1];
var lenlen = 0;
// Seek length of length if length is greater than 127 (i.e. two 512-bit / 64-byte R and S values)
if (0x80 & len) {
lenlen = len - 0x80;
// the length of the signature won't be over 256 bytes (2048 bits) for many years yet
if (1 !== lenlen) { return binsig; }
// the length is this number
len = binsig[2];
lenlen = len - 0x80; // should be exactly 1
len = binsig[2]; // should be <= 130 (two 64-bit SHA-512s, plus padding)
index += lenlen;
}
// should have bigint header of 0x02 followd by a single byte of length
if (0x02 !== binsig[index]) { return binsig; }
// should be of BigInt type
if (0x02 !== binsig[index]) { throw new Error("Impossible EC SHA R marker"); }
index += 1;
var rlen = binsig[index];
var r = binsig.slice(index + 1, index + 1 + rlen);
var bits = 32;
if (rlen > 49) {
bits = 64;
} else if (rlen > 33) {
bits = 48;
}
var r = binsig.slice(index + 1, index + 1 + rlen).toString('hex');
var slen = binsig[index + 1 + rlen + 1]; // skip header and read length
var s = binsig.slice(index + 1 + rlen + 1 + 1);
if (slen !== s.byteLength) { return binsig; }
var s = binsig.slice(index + 1 + rlen + 1 + 1).toString('hex');
if (2 *slen !== s.length) { throw new Error("Impossible EC SHA S length"); }
// There may be one byte of padding on either
if (33 === r.byteLength) { r = r.slice(1); }
if (33 === s.byteLength) { s = s.slice(1); }
return Buffer.concat([r, s]);
while (r.length < 2*bits) { r = '00' + r; }
while (s.length < 2*bits) { s = '00' + s; }
if (2*(bits+1) === r.length) { r = r.slice(2); }
if (2*(bits+1) === s.length) { s = s.slice(2); }
return Buffer.concat([Buffer.from(r, 'hex'), Buffer.from(s, 'hex')]);
}
if (opts.pem && opts.jwk) {

2
package.json
View File

@ -1,6 +1,6 @@
{
"name": "keypairs",
"version": "1.2.11",
"version": "1.2.12",
"description": "Lightweight RSA/ECDSA keypair generation and JWK <-> PEM",
"main": "keypairs.js",
"files": [