acme.js/lib/node/keypairs.js

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'use strict';
var Keypairs = module.exports;
var crypto = require('crypto');
Keypairs._sign = function(opts, payload) {
return Keypairs._import(opts).then(function(pem) {
payload = Buffer.from(payload);
// node specifies RSA-SHAxxx even when it's actually ecdsa (it's all encoded x509 shasums anyway)
// TODO opts.alg = (protect||header).alg
var nodeAlg = 'SHA' + Keypairs._getBits(opts);
var binsig = crypto
.createSign(nodeAlg)
.update(payload)
.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
// https://tools.ietf.org/html/rfc7518#section-3.4
binsig = Keypairs._ecdsaAsn1SigToJoseSig(binsig);
}
return binsig;
});
};
Keypairs._import = function(opts) {
if (opts.pem && opts.jwk) {
return Promise.resolve(opts.pem);
} else {
// XXX added by caller
return Keypairs.export({ jwk: opts.jwk });
}
};
Keypairs._ecdsaAsn1SigToJoseSig = function(binsig) {
// should have asn1 sequence header of 0x30
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; // should be exactly 1
len = binsig[2]; // should be <= 130 (two 64-bit SHA-512s, plus padding)
index += lenlen;
}
// should be of BigInt type
if (0x02 !== binsig[index]) {
throw new Error('Impossible EC SHA R marker');
}
index += 1;
var rlen = binsig[index];
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).toString('hex');
if (2 * slen !== s.length) {
throw new Error('Impossible EC SHA S length');
}
// There may be one byte of padding on either
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')]);
};