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84 lines
2.4 KiB
84 lines
2.4 KiB
// much of this based on https://github.com/indutny/self-signed/blob/gh-pages/lib/rsa.js |
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var Buffer = require('safe-buffer').Buffer |
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var BN = require('bn.js') |
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var EC = require('elliptic').ec |
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var parseKeys = require('parse-asn1') |
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var curves = require('./curves.json') |
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function verify (sig, hash, key, signType, tag) { |
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var pub = parseKeys(key) |
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if (pub.type === 'ec') { |
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// rsa keys can be interpreted as ecdsa ones in openssl |
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if (signType !== 'ecdsa' && signType !== 'ecdsa/rsa') throw new Error('wrong public key type') |
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return ecVerify(sig, hash, pub) |
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} else if (pub.type === 'dsa') { |
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if (signType !== 'dsa') throw new Error('wrong public key type') |
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return dsaVerify(sig, hash, pub) |
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} else { |
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if (signType !== 'rsa' && signType !== 'ecdsa/rsa') throw new Error('wrong public key type') |
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} |
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hash = Buffer.concat([tag, hash]) |
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var len = pub.modulus.byteLength() |
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var pad = [1] |
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var padNum = 0 |
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while (hash.length + pad.length + 2 < len) { |
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pad.push(0xff) |
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padNum++ |
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} |
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pad.push(0x00) |
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var i = -1 |
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while (++i < hash.length) { |
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pad.push(hash[i]) |
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} |
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pad = Buffer.from(pad) |
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var red = BN.mont(pub.modulus) |
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sig = new BN(sig).toRed(red) |
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sig = sig.redPow(new BN(pub.publicExponent)) |
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sig = Buffer.from(sig.fromRed().toArray()) |
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var out = padNum < 8 ? 1 : 0 |
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len = Math.min(sig.length, pad.length) |
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if (sig.length !== pad.length) out = 1 |
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i = -1 |
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while (++i < len) out |= sig[i] ^ pad[i] |
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return out === 0 |
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} |
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function ecVerify (sig, hash, pub) { |
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var curveId = curves[pub.data.algorithm.curve.join('.')] |
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if (!curveId) throw new Error('unknown curve ' + pub.data.algorithm.curve.join('.')) |
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var curve = new EC(curveId) |
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var pubkey = pub.data.subjectPrivateKey.data |
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return curve.verify(hash, sig, pubkey) |
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} |
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function dsaVerify (sig, hash, pub) { |
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var p = pub.data.p |
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var q = pub.data.q |
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var g = pub.data.g |
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var y = pub.data.pub_key |
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var unpacked = parseKeys.signature.decode(sig, 'der') |
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var s = unpacked.s |
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var r = unpacked.r |
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checkValue(s, q) |
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checkValue(r, q) |
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var montp = BN.mont(p) |
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var w = s.invm(q) |
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var v = g.toRed(montp) |
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.redPow(new BN(hash).mul(w).mod(q)) |
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.fromRed() |
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.mul(y.toRed(montp).redPow(r.mul(w).mod(q)).fromRed()) |
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.mod(p) |
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.mod(q) |
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return v.cmp(r) === 0 |
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} |
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function checkValue (b, q) { |
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if (b.cmpn(0) <= 0) throw new Error('invalid sig') |
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if (b.cmp(q) >= q) throw new Error('invalid sig') |
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} |
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module.exports = verify
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