| // Copyright 2018 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 signature |
| |
| import ( |
| "errors" |
| "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" |
| tinkpb "github.com/google/tink/go/proto/tink_go_proto" |
| ) |
| |
| // NewVerifier returns a Verifier primitive from the given keyset handle. |
| func NewVerifier(h *keyset.Handle) (tink.Verifier, error) { |
| return NewVerifierWithKeyManager(h, nil /*keyManager*/) |
| } |
| |
| // NewVerifierWithKeyManager returns a Verifier primitive from the given keyset handle and custom key manager. |
| // Deprecated: register the KeyManager and use New above. |
| func NewVerifierWithKeyManager(h *keyset.Handle, km registry.KeyManager) (tink.Verifier, error) { |
| ps, err := h.PrimitivesWithKeyManager(km) |
| if err != nil { |
| return nil, fmt.Errorf("verifier_factory: cannot obtain primitive set: %s", err) |
| } |
| return newWrappedVerifier(ps) |
| } |
| |
| // verifierSet is a Verifier implementation that uses the |
| // underlying primitive set for verifying. |
| type wrappedVerifier struct { |
| ps *primitiveset.PrimitiveSet |
| } |
| |
| // Asserts that verifierSet implements the Verifier interface. |
| var _ tink.Verifier = (*wrappedVerifier)(nil) |
| |
| func newWrappedVerifier(ps *primitiveset.PrimitiveSet) (*wrappedVerifier, error) { |
| if _, ok := (ps.Primary.Primitive).(tink.Verifier); !ok { |
| return nil, fmt.Errorf("verifier_factory: not a Verifier primitive") |
| } |
| |
| for _, primitives := range ps.Entries { |
| for _, p := range primitives { |
| if _, ok := (p.Primitive).(tink.Verifier); !ok { |
| return nil, fmt.Errorf("verifier_factory: not an Verifier primitive") |
| } |
| } |
| } |
| |
| ret := new(wrappedVerifier) |
| ret.ps = ps |
| |
| return ret, nil |
| } |
| |
| var errInvalidSignature = errors.New("verifier_factory: invalid signature") |
| |
| // Verify checks whether the given signature is a valid signature of the given data. |
| func (v *wrappedVerifier) Verify(signature, data []byte) error { |
| prefixSize := cryptofmt.NonRawPrefixSize |
| if len(signature) < prefixSize { |
| return errInvalidSignature |
| } |
| |
| // try non-raw keys |
| prefix := signature[:prefixSize] |
| signatureNoPrefix := signature[prefixSize:] |
| entries, err := v.ps.EntriesForPrefix(string(prefix)) |
| if err == nil { |
| for i := 0; i < len(entries); i++ { |
| var signedData []byte |
| if entries[i].PrefixType == tinkpb.OutputPrefixType_LEGACY { |
| signedData = append(data, byte(0)) |
| } else { |
| signedData = data |
| } |
| |
| verifier, ok := (entries[i].Primitive).(tink.Verifier) |
| if !ok { |
| return fmt.Errorf("verifier_factory: not an Verifier primitive") |
| } |
| |
| if err = verifier.Verify(signatureNoPrefix, signedData); err == nil { |
| return nil |
| } |
| } |
| } |
| |
| // try raw keys |
| entries, err = v.ps.RawEntries() |
| if err == nil { |
| for i := 0; i < len(entries); i++ { |
| verifier, ok := (entries[i].Primitive).(tink.Verifier) |
| if !ok { |
| return fmt.Errorf("verifier_factory: not an Verifier primitive") |
| } |
| |
| if err = verifier.Verify(signature, data); err == nil { |
| return nil |
| } |
| } |
| } |
| |
| return errInvalidSignature |
| } |