--- /dev/null
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+ "bytes"
+ "crypto/cipher"
+ "io"
+ "strconv"
+
+ "golang.org/x/crypto/openpgp/errors"
+ "golang.org/x/crypto/openpgp/s2k"
+)
+
+// This is the largest session key that we'll support. Since no 512-bit cipher
+// has even been seriously used, this is comfortably large.
+const maxSessionKeySizeInBytes = 64
+
+// SymmetricKeyEncrypted represents a passphrase protected session key. See RFC
+// 4880, section 5.3.
+type SymmetricKeyEncrypted struct {
+ CipherFunc CipherFunction
+ s2k func(out, in []byte)
+ encryptedKey []byte
+}
+
+const symmetricKeyEncryptedVersion = 4
+
+func (ske *SymmetricKeyEncrypted) parse(r io.Reader) error {
+ // RFC 4880, section 5.3.
+ var buf [2]byte
+ if _, err := readFull(r, buf[:]); err != nil {
+ return err
+ }
+ if buf[0] != symmetricKeyEncryptedVersion {
+ return errors.UnsupportedError("SymmetricKeyEncrypted version")
+ }
+ ske.CipherFunc = CipherFunction(buf[1])
+
+ if ske.CipherFunc.KeySize() == 0 {
+ return errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(buf[1])))
+ }
+
+ var err error
+ ske.s2k, err = s2k.Parse(r)
+ if err != nil {
+ return err
+ }
+
+ encryptedKey := make([]byte, maxSessionKeySizeInBytes)
+ // The session key may follow. We just have to try and read to find
+ // out. If it exists then we limit it to maxSessionKeySizeInBytes.
+ n, err := readFull(r, encryptedKey)
+ if err != nil && err != io.ErrUnexpectedEOF {
+ return err
+ }
+
+ if n != 0 {
+ if n == maxSessionKeySizeInBytes {
+ return errors.UnsupportedError("oversized encrypted session key")
+ }
+ ske.encryptedKey = encryptedKey[:n]
+ }
+
+ return nil
+}
+
+// Decrypt attempts to decrypt an encrypted session key and returns the key and
+// the cipher to use when decrypting a subsequent Symmetrically Encrypted Data
+// packet.
+func (ske *SymmetricKeyEncrypted) Decrypt(passphrase []byte) ([]byte, CipherFunction, error) {
+ key := make([]byte, ske.CipherFunc.KeySize())
+ ske.s2k(key, passphrase)
+
+ if len(ske.encryptedKey) == 0 {
+ return key, ske.CipherFunc, nil
+ }
+
+ // the IV is all zeros
+ iv := make([]byte, ske.CipherFunc.blockSize())
+ c := cipher.NewCFBDecrypter(ske.CipherFunc.new(key), iv)
+ plaintextKey := make([]byte, len(ske.encryptedKey))
+ c.XORKeyStream(plaintextKey, ske.encryptedKey)
+ cipherFunc := CipherFunction(plaintextKey[0])
+ if cipherFunc.blockSize() == 0 {
+ return nil, ske.CipherFunc, errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(cipherFunc)))
+ }
+ plaintextKey = plaintextKey[1:]
+ if l, cipherKeySize := len(plaintextKey), cipherFunc.KeySize(); l != cipherFunc.KeySize() {
+ return nil, cipherFunc, errors.StructuralError("length of decrypted key (" + strconv.Itoa(l) + ") " +
+ "not equal to cipher keysize (" + strconv.Itoa(cipherKeySize) + ")")
+ }
+ return plaintextKey, cipherFunc, nil
+}
+
+// SerializeSymmetricKeyEncrypted serializes a symmetric key packet to w. The
+// packet contains a random session key, encrypted by a key derived from the
+// given passphrase. The session key is returned and must be passed to
+// SerializeSymmetricallyEncrypted.
+// If config is nil, sensible defaults will be used.
+func SerializeSymmetricKeyEncrypted(w io.Writer, passphrase []byte, config *Config) (key []byte, err error) {
+ cipherFunc := config.Cipher()
+ keySize := cipherFunc.KeySize()
+ if keySize == 0 {
+ return nil, errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(cipherFunc)))
+ }
+
+ s2kBuf := new(bytes.Buffer)
+ keyEncryptingKey := make([]byte, keySize)
+ // s2k.Serialize salts and stretches the passphrase, and writes the
+ // resulting key to keyEncryptingKey and the s2k descriptor to s2kBuf.
+ err = s2k.Serialize(s2kBuf, keyEncryptingKey, config.Random(), passphrase, &s2k.Config{Hash: config.Hash(), S2KCount: config.PasswordHashIterations()})
+ if err != nil {
+ return
+ }
+ s2kBytes := s2kBuf.Bytes()
+
+ packetLength := 2 /* header */ + len(s2kBytes) + 1 /* cipher type */ + keySize
+ err = serializeHeader(w, packetTypeSymmetricKeyEncrypted, packetLength)
+ if err != nil {
+ return
+ }
+
+ var buf [2]byte
+ buf[0] = symmetricKeyEncryptedVersion
+ buf[1] = byte(cipherFunc)
+ _, err = w.Write(buf[:])
+ if err != nil {
+ return
+ }
+ _, err = w.Write(s2kBytes)
+ if err != nil {
+ return
+ }
+
+ sessionKey := make([]byte, keySize)
+ _, err = io.ReadFull(config.Random(), sessionKey)
+ if err != nil {
+ return
+ }
+ iv := make([]byte, cipherFunc.blockSize())
+ c := cipher.NewCFBEncrypter(cipherFunc.new(keyEncryptingKey), iv)
+ encryptedCipherAndKey := make([]byte, keySize+1)
+ c.XORKeyStream(encryptedCipherAndKey, buf[1:])
+ c.XORKeyStream(encryptedCipherAndKey[1:], sessionKey)
+ _, err = w.Write(encryptedCipherAndKey)
+ if err != nil {
+ return
+ }
+
+ key = sessionKey
+ return
+}
projects / github / fretlink / terraform-provider-statuscake.git / blobdiff