57 lines
2.1 KiB
JavaScript
57 lines
2.1 KiB
JavaScript
const { pbkdf2Sync: pbkdf2, randomBytes } = require('crypto')
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const { KEYOBJECT } = require('../help/consts')
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const base64url = require('../help/base64url')
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const SALT_LENGTH = 16
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const NULL_BUFFER = Buffer.alloc(1, 0)
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const concatSalt = (alg, p2s) => {
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return Buffer.concat([
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Buffer.from(alg, 'utf8'),
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NULL_BUFFER,
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p2s
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])
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}
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const wrapKey = (keylen, sha, concat, wrap, { [KEYOBJECT]: keyObject }, payload) => {
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// Note that if password-based encryption is used for multiple
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// recipients, it is expected that each recipient use different values
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// for the PBES2 parameters "p2s" and "p2c".
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// here we generate p2c between 2048 and 4096 and random p2s
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const p2c = Math.floor((Math.random() * 2049) + 2048)
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const p2s = randomBytes(SALT_LENGTH)
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const salt = concat(p2s)
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const derivedKey = pbkdf2(keyObject.export(), salt, p2c, keylen, sha)
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const result = wrap({ [KEYOBJECT]: derivedKey }, payload)
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result.header = result.header || {}
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Object.assign(result.header, { p2c, p2s: base64url.encodeBuffer(p2s) })
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return result
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}
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const unwrapKey = (keylen, sha, concat, unwrap, { [KEYOBJECT]: keyObject }, payload, header) => {
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const { p2s, p2c } = header
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const salt = concat(p2s)
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const derivedKey = pbkdf2(keyObject.export(), salt, p2c, keylen, sha)
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return unwrap({ [KEYOBJECT]: derivedKey }, payload, header)
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}
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module.exports = (JWA, JWK) => {
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['PBES2-HS256+A128KW', 'PBES2-HS384+A192KW', 'PBES2-HS512+A256KW'].forEach((jwaAlg) => {
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const kw = jwaAlg.substr(-6)
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const kwWrap = JWA.keyManagementEncrypt.get(kw)
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const kwUnwrap = JWA.keyManagementDecrypt.get(kw)
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const keylen = parseInt(jwaAlg.substr(13, 3), 10) / 8
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const sha = `sha${jwaAlg.substr(8, 3)}`
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if (kwWrap && kwUnwrap) {
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JWA.keyManagementEncrypt.set(jwaAlg, wrapKey.bind(undefined, keylen, sha, concatSalt.bind(undefined, jwaAlg), kwWrap))
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JWA.keyManagementDecrypt.set(jwaAlg, unwrapKey.bind(undefined, keylen, sha, concatSalt.bind(undefined, jwaAlg), kwUnwrap))
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JWK.oct.deriveKey[jwaAlg] = key => key.use === 'enc' || key.use === undefined
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}
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})
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}
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