forked from lestrrat-go/jwx
/
cipher.go
188 lines (167 loc) · 4.54 KB
/
cipher.go
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package jwe
import (
"crypto/aes"
"crypto/cipher"
"crypto/rsa"
"fmt"
"github.com/lestrrat-go/jwx/internal/debug"
"github.com/lestrrat-go/jwx/jwa"
"github.com/lestrrat-go/jwx/jwe/aescbc"
"github.com/pkg/errors"
)
const (
TagSize = 16
)
func (f AeadFetchFunc) AeadFetch(key []byte) (cipher.AEAD, error) {
return f(key)
}
var GcmAeadFetch = AeadFetchFunc(func(key []byte) (cipher.AEAD, error) {
aescipher, err := aes.NewCipher(key)
if err != nil {
if debug.Enabled {
debug.Printf("GcmAeadFetch: failed to create cipher")
}
return nil, errors.Wrap(err, "cipher: failed to create AES cipher for GCM")
}
aead, err := cipher.NewGCM(aescipher)
if err != nil {
return nil, errors.Wrap(err, `failed to create GCM for cipher`)
}
return aead, nil
})
var CbcAeadFetch = AeadFetchFunc(func(key []byte) (cipher.AEAD, error) {
if debug.Enabled {
debug.Printf("CbcAeadFetch: fetching key (%d)", len(key))
}
aead, err := aescbc.New(key, aes.NewCipher)
if err != nil {
if debug.Enabled {
debug.Printf("CbcAeadFetch: failed to create aead fetcher %v (%d): %s", key, len(key), err)
}
return nil, errors.Wrap(err, "cipher: failed to create AES cipher for CBC")
}
return aead, nil
})
func (c AesContentCipher) KeySize() int {
return c.keysize
}
func (c AesContentCipher) TagSize() int {
return c.tagsize
}
func NewAesContentCipher(alg jwa.ContentEncryptionAlgorithm) (*AesContentCipher, error) {
var keysize int
var fetcher AeadFetcher
switch alg {
case jwa.A128GCM:
keysize = 16
fetcher = GcmAeadFetch
case jwa.A192GCM:
keysize = 24
fetcher = GcmAeadFetch
case jwa.A256GCM:
keysize = 32
fetcher = GcmAeadFetch
case jwa.A128CBC_HS256:
keysize = 16 * 2
fetcher = CbcAeadFetch
case jwa.A192CBC_HS384:
keysize = 24 * 2
fetcher = CbcAeadFetch
case jwa.A256CBC_HS512:
keysize = 32 * 2
fetcher = CbcAeadFetch
default:
return nil, errors.Wrap(ErrUnsupportedAlgorithm, "failed to create AES content cipher")
}
return &AesContentCipher{
keysize: keysize,
tagsize: TagSize,
AeadFetcher: fetcher,
}, nil
}
func (c AesContentCipher) encrypt(cek, plaintext, aad []byte) (iv, ciphertext, tag []byte, err error) {
var aead cipher.AEAD
aead, err = c.AeadFetch(cek)
if err != nil {
if debug.Enabled {
debug.Printf("AeadFetch failed: %s", err)
}
return nil, nil, nil, errors.Wrap(err, "failed to fetch AEAD")
}
// Seal may panic (argh!), so protect ourselves from that
defer func() {
if e := recover(); e != nil {
switch e.(type) {
case error:
err = e.(error)
case string:
err = errors.New(e.(string))
default:
err = fmt.Errorf("%s", e)
}
err = errors.Wrap(err, "failed to descrypt")
}
}()
var bs ByteSource
if c.NonceGenerator == nil {
bs, err = NewRandomKeyGenerate(aead.NonceSize()).KeyGenerate()
} else {
bs, err = c.NonceGenerator.KeyGenerate()
}
if err != nil {
return nil, nil, nil, errors.Wrap(err, "failed to generate nonce")
}
iv = bs.Bytes()
combined := aead.Seal(nil, iv, plaintext, aad)
tagoffset := len(combined) - c.TagSize()
if debug.Enabled {
debug.Printf("tagsize = %d", c.TagSize())
}
tag = combined[tagoffset:]
ciphertext = make([]byte, tagoffset)
copy(ciphertext, combined[:tagoffset])
if debug.Enabled {
debug.Printf("encrypt: combined = %x (%d)\n", combined, len(combined))
debug.Printf("encrypt: ciphertext = %x (%d)\n", ciphertext, len(ciphertext))
debug.Printf("encrypt: tag = %x (%d)\n", tag, len(tag))
debug.Printf("finally ciphertext = %x\n", ciphertext)
}
return
}
func (c AesContentCipher) decrypt(cek, iv, ciphertxt, tag, aad []byte) (plaintext []byte, err error) {
aead, err := c.AeadFetch(cek)
if err != nil {
if debug.Enabled {
debug.Printf("AeadFetch failed for %v: %s", cek, err)
}
return nil, errors.Wrap(err, "failed to fetch AEAD data")
}
// Open may panic (argh!), so protect ourselves from that
defer func() {
if e := recover(); e != nil {
switch e.(type) {
case error:
err = e.(error)
case string:
err = errors.New(e.(string))
default:
err = fmt.Errorf("%s", e)
}
err = errors.Wrap(err, "failed to decrypt")
return
}
}()
combined := make([]byte, len(ciphertxt)+len(tag))
copy(combined, ciphertxt)
copy(combined[len(ciphertxt):], tag)
if debug.Enabled {
debug.Printf("AesContentCipher.decrypt: combined = %x (%d)", combined, len(combined))
}
plaintext, err = aead.Open(nil, iv, combined, aad)
return
}
func NewRsaContentCipher(alg jwa.ContentEncryptionAlgorithm, pubkey *rsa.PublicKey) (*RsaContentCipher, error) {
return &RsaContentCipher{
pubkey: pubkey,
}, nil
}