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decrypt_key_management.ts
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decrypt_key_management.ts
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import { unwrap as aesKw } from '../runtime/aeskw.ts'
import * as ECDH from '../runtime/ecdhes.ts'
import { decrypt as pbes2Kw } from '../runtime/pbes2kw.ts'
import { decrypt as rsaEs } from '../runtime/rsaes.ts'
import { decode as base64url } from '../runtime/base64url.ts'
import type { JWEHeaderParameters, KeyLike, JWK } from '../types.d.ts'
import { JOSENotSupported, JWEInvalid } from '../util/errors.ts'
import { bitLength as cekLength } from '../lib/cek.ts'
import { importJWK } from '../key/import.ts'
import checkKeyType from './check_key_type.ts'
import isObject from './is_object.ts'
import { unwrap as aesGcmKw } from './aesgcmkw.ts'
async function decryptKeyManagement(
alg: string,
key: KeyLike | Uint8Array,
encryptedKey: Uint8Array | undefined,
joseHeader: JWEHeaderParameters,
): Promise<KeyLike | Uint8Array> {
checkKeyType(alg, key, 'decrypt')
switch (alg) {
case 'dir': {
// Direct Encryption
if (encryptedKey !== undefined)
throw new JWEInvalid('Encountered unexpected JWE Encrypted Key')
return key
}
case 'ECDH-ES':
// Direct Key Agreement
if (encryptedKey !== undefined)
throw new JWEInvalid('Encountered unexpected JWE Encrypted Key')
case 'ECDH-ES+A128KW':
case 'ECDH-ES+A192KW':
case 'ECDH-ES+A256KW': {
// Direct Key Agreement
if (!isObject<JWK>(joseHeader.epk))
throw new JWEInvalid(`JOSE Header "epk" (Ephemeral Public Key) missing or invalid`)
if (!ECDH.ecdhAllowed(key))
throw new JOSENotSupported(
'ECDH with the provided key is not allowed or not supported by your javascript runtime',
)
const epk = await importJWK(joseHeader.epk, alg)
let partyUInfo!: Uint8Array
let partyVInfo!: Uint8Array
if (joseHeader.apu !== undefined) {
if (typeof joseHeader.apu !== 'string')
throw new JWEInvalid(`JOSE Header "apu" (Agreement PartyUInfo) invalid`)
partyUInfo = base64url(joseHeader.apu)
}
if (joseHeader.apv !== undefined) {
if (typeof joseHeader.apv !== 'string')
throw new JWEInvalid(`JOSE Header "apv" (Agreement PartyVInfo) invalid`)
partyVInfo = base64url(joseHeader.apv)
}
const sharedSecret = await ECDH.deriveKey(
epk,
key,
alg === 'ECDH-ES' ? joseHeader.enc! : alg,
alg === 'ECDH-ES' ? cekLength(joseHeader.enc!) : parseInt(alg.slice(-5, -2), 10),
partyUInfo,
partyVInfo,
)
if (alg === 'ECDH-ES') return sharedSecret
// Key Agreement with Key Wrapping
if (encryptedKey === undefined) throw new JWEInvalid('JWE Encrypted Key missing')
return aesKw(alg.slice(-6), sharedSecret, encryptedKey)
}
case 'RSA1_5':
case 'RSA-OAEP':
case 'RSA-OAEP-256':
case 'RSA-OAEP-384':
case 'RSA-OAEP-512': {
// Key Encryption (RSA)
if (encryptedKey === undefined) throw new JWEInvalid('JWE Encrypted Key missing')
return rsaEs(alg, key, encryptedKey)
}
case 'PBES2-HS256+A128KW':
case 'PBES2-HS384+A192KW':
case 'PBES2-HS512+A256KW': {
// Key Encryption (PBES2)
if (encryptedKey === undefined) throw new JWEInvalid('JWE Encrypted Key missing')
if (typeof joseHeader.p2c !== 'number')
throw new JWEInvalid(`JOSE Header "p2c" (PBES2 Count) missing or invalid`)
if (typeof joseHeader.p2s !== 'string')
throw new JWEInvalid(`JOSE Header "p2s" (PBES2 Salt) missing or invalid`)
return pbes2Kw(alg, key, encryptedKey, joseHeader.p2c, base64url(joseHeader.p2s))
}
case 'A128KW':
case 'A192KW':
case 'A256KW': {
// Key Wrapping (AES KW)
if (encryptedKey === undefined) throw new JWEInvalid('JWE Encrypted Key missing')
return aesKw(alg, key, encryptedKey)
}
case 'A128GCMKW':
case 'A192GCMKW':
case 'A256GCMKW': {
// Key Wrapping (AES GCM KW)
if (encryptedKey === undefined) throw new JWEInvalid('JWE Encrypted Key missing')
if (typeof joseHeader.iv !== 'string')
throw new JWEInvalid(`JOSE Header "iv" (Initialization Vector) missing or invalid`)
if (typeof joseHeader.tag !== 'string')
throw new JWEInvalid(`JOSE Header "tag" (Authentication Tag) missing or invalid`)
const iv = base64url(joseHeader.iv)
const tag = base64url(joseHeader.tag)
return aesGcmKw(alg, key, encryptedKey, iv, tag)
}
default: {
throw new JOSENotSupported('Invalid or unsupported "alg" (JWE Algorithm) header value')
}
}
}
export default decryptKeyManagement