85 lines
2.3 KiB
JavaScript
85 lines
2.3 KiB
JavaScript
'use strict';
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var Keypairs = module.exports;
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var crypto = require('crypto');
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Keypairs._sign = function(opts, payload) {
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return Keypairs._import(opts).then(function(pem) {
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payload = Buffer.from(payload);
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// node specifies RSA-SHAxxx even when it's actually ecdsa (it's all encoded x509 shasums anyway)
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// TODO opts.alg = (protect||header).alg
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var nodeAlg = 'SHA' + Keypairs._getBits(opts);
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var binsig = crypto
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.createSign(nodeAlg)
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.update(payload)
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.sign(pem);
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if ('EC' === opts.jwk.kty && !/x509|asn1/i.test(opts.format)) {
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// ECDSA JWT signatures differ from "normal" ECDSA signatures
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// https://tools.ietf.org/html/rfc7518#section-3.4
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binsig = Keypairs._ecdsaAsn1SigToJoseSig(binsig);
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}
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return binsig;
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});
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};
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Keypairs._import = function(opts) {
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if (opts.pem && opts.jwk) {
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return Promise.resolve(opts.pem);
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} else {
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// XXX added by caller
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return Keypairs.export({ jwk: opts.jwk });
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}
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};
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Keypairs._ecdsaAsn1SigToJoseSig = function(binsig) {
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// should have asn1 sequence header of 0x30
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if (0x30 !== binsig[0]) {
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throw new Error('Impossible EC SHA head marker');
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}
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var index = 2; // first ecdsa "R" header byte
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var len = binsig[1];
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var lenlen = 0;
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// Seek length of length if length is greater than 127 (i.e. two 512-bit / 64-byte R and S values)
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if (0x80 & len) {
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lenlen = len - 0x80; // should be exactly 1
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len = binsig[2]; // should be <= 130 (two 64-bit SHA-512s, plus padding)
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index += lenlen;
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}
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// should be of BigInt type
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if (0x02 !== binsig[index]) {
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throw new Error('Impossible EC SHA R marker');
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}
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index += 1;
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var rlen = binsig[index];
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var bits = 32;
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if (rlen > 49) {
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bits = 64;
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} else if (rlen > 33) {
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bits = 48;
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}
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var r = binsig.slice(index + 1, index + 1 + rlen).toString('hex');
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var slen = binsig[index + 1 + rlen + 1]; // skip header and read length
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var s = binsig.slice(index + 1 + rlen + 1 + 1).toString('hex');
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if (2 * slen !== s.length) {
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throw new Error('Impossible EC SHA S length');
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}
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// There may be one byte of padding on either
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while (r.length < 2 * bits) {
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r = '00' + r;
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}
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while (s.length < 2 * bits) {
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s = '00' + s;
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}
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if (2 * (bits + 1) === r.length) {
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r = r.slice(2);
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}
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if (2 * (bits + 1) === s.length) {
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s = s.slice(2);
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}
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return Buffer.concat([Buffer.from(r, 'hex'), Buffer.from(s, 'hex')]);
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};
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