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pkg/cryptstate: add Overhead(); use it internally.

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This commit is contained in:
Mikkel Krautz 2012-12-08 23:39:19 +01:00
parent 56b174d983
commit eacf839182
1 changed files with 8 additions and 2 deletions
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10
pkg/cryptstate/cryptstate.go
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@ -97,12 +97,18 @@ func (cs *CryptState) SetKey(key []byte, eiv []byte, div []byte) error {
return nil return nil
} }
// Overhead returns the length, in bytes, that a ciphertext
// is longer than a plaintext.
func (cs *CryptState) Overhead() int {
return 1 + cs.mode.Overhead()
}
func (cs *CryptState) Decrypt(dst, src []byte) error { func (cs *CryptState) Decrypt(dst, src []byte) error {
if len(src) < 4 { if len(src) < cs.Overhead() {
return errors.New("cryptstate: crypted length too short to decrypt") return errors.New("cryptstate: crypted length too short to decrypt")
} }
plain_len := len(src) - 4 plain_len := len(src) - cs.Overhead()
if len(dst) != plain_len { if len(dst) != plain_len {
return errors.New("cryptstate: plain_len and src len mismatch") return errors.New("cryptstate: plain_len and src len mismatch")
} }