| // Copyright 2019 Google LLC |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| // |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| package hybrid |
| |
| import ( |
| "fmt" |
| |
| "github.com/google/tink/go/core/cryptofmt" |
| "github.com/google/tink/go/core/primitiveset" |
| "github.com/google/tink/go/core/registry" |
| "github.com/google/tink/go/keyset" |
| "github.com/google/tink/go/tink" |
| ) |
| |
| // NewHybridDecrypt returns an HybridDecrypt primitive from the given keyset handle. |
| func NewHybridDecrypt(h *keyset.Handle) (tink.HybridDecrypt, error) { |
| return NewHybridDecryptWithKeyManager(h, nil /*keyManager*/) |
| } |
| |
| // NewHybridDecryptWithKeyManager returns an HybridDecrypt primitive from the given keyset handle |
| // and custom key manager. |
| // Deprecated: register the KeyManager and use New above. |
| func NewHybridDecryptWithKeyManager(h *keyset.Handle, km registry.KeyManager) (tink.HybridDecrypt, error) { |
| ps, err := h.PrimitivesWithKeyManager(km) |
| if err != nil { |
| return nil, fmt.Errorf("hybrid_factory: cannot obtain primitive set: %s", err) |
| } |
| |
| return newWrappedHybridDecrypt(ps) |
| } |
| |
| // wrappedHybridDecrypt is an HybridDecrypt implementation that uses the underlying primitive set |
| // for decryption. |
| type wrappedHybridDecrypt struct { |
| ps *primitiveset.PrimitiveSet |
| } |
| |
| func newWrappedHybridDecrypt(ps *primitiveset.PrimitiveSet) (*wrappedHybridDecrypt, error) { |
| if _, ok := (ps.Primary.Primitive).(tink.HybridDecrypt); !ok { |
| return nil, fmt.Errorf("hybrid_factory: not a HybridDecrypt primitive") |
| } |
| |
| for _, primitives := range ps.Entries { |
| for _, p := range primitives { |
| if _, ok := (p.Primitive).(tink.HybridDecrypt); !ok { |
| return nil, fmt.Errorf("hybrid_factory: not a HybridDecrypt primitive") |
| } |
| } |
| } |
| |
| ret := new(wrappedHybridDecrypt) |
| ret.ps = ps |
| |
| return ret, nil |
| } |
| |
| // Decrypt decrypts the given ciphertext, verifying the integrity of contextInfo. |
| // It returns the corresponding plaintext if the ciphertext is authenticated. |
| func (a *wrappedHybridDecrypt) Decrypt(ciphertext, contextInfo []byte) ([]byte, error) { |
| // try non-raw keys |
| prefixSize := cryptofmt.NonRawPrefixSize |
| if len(ciphertext) > prefixSize { |
| prefix := ciphertext[:prefixSize] |
| ctNoPrefix := ciphertext[prefixSize:] |
| entries, err := a.ps.EntriesForPrefix(string(prefix)) |
| if err == nil { |
| for i := 0; i < len(entries); i++ { |
| p, ok := (entries[i].Primitive).(tink.HybridDecrypt) |
| if !ok { |
| return nil, fmt.Errorf("hybrid_factory: not a HybridDecrypt primitive") |
| } |
| |
| pt, err := p.Decrypt(ctNoPrefix, contextInfo) |
| if err == nil { |
| return pt, nil |
| } |
| } |
| } |
| } |
| |
| // try raw keys |
| entries, err := a.ps.RawEntries() |
| if err == nil { |
| for i := 0; i < len(entries); i++ { |
| p, ok := (entries[i].Primitive).(tink.HybridDecrypt) |
| if !ok { |
| return nil, fmt.Errorf("hybrid_factory: not a HybridDecrypt primitive") |
| } |
| |
| pt, err := p.Decrypt(ciphertext, contextInfo) |
| if err == nil { |
| return pt, nil |
| } |
| } |
| } |
| |
| // nothing worked |
| return nil, fmt.Errorf("hybrid_factory: decryption failed") |
| } |