// 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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