Adding upstream version 0.0~git20250502.5100632.

Signed-off-by: Daniel Baumann <daniel@debian.org>

encode.go

@@ -0,0 +1,95 @@
+// Modified by 42wim
+//
+// Copyright 2021 The Sigstore Authors.
+//
+// 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 sshsig
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/42wim/sshsig/pem"
+
+	"golang.org/x/crypto/ssh"
+)
+
+const (
+	pemType = "SSH SIGNATURE"
+)
+
+// Armored returns the signature in an armored format.
+func Armor(s *ssh.Signature, p ssh.PublicKey, ns string) []byte {
+	sig := WrappedSig{
+		Version:       1,
+		PublicKey:     string(p.Marshal()),
+		Namespace:     ns,
+		HashAlgorithm: defaultHashAlgorithm,
+		Signature:     string(ssh.Marshal(s)),
+	}
+
+	copy(sig.MagicHeader[:], magicHeader)
+
+	enc := pem.EncodeToMemory(&pem.Block{
+		Type:  pemType,
+		Bytes: ssh.Marshal(sig),
+	})
+	return enc
+}
+
+// Decode parses an armored signature.
+func Decode(b []byte) (*Signature, error) {
+	pemBlock, _ := pem.Decode(b)
+	if pemBlock == nil {
+		return nil, errors.New("unable to decode pem file")
+	}
+
+	if pemBlock.Type != pemType {
+		return nil, fmt.Errorf("wrong pem block type: %s. Expected SSH-SIGNATURE", pemBlock.Type)
+	}
+
+	// Now we unmarshal it into the Signature block
+	sig := WrappedSig{}
+	if err := ssh.Unmarshal(pemBlock.Bytes, &sig); err != nil {
+		return nil, err
+	}
+
+	if sig.Version != 1 {
+		return nil, fmt.Errorf("unsupported signature version: %d", sig.Version)
+	}
+	if string(sig.MagicHeader[:]) != magicHeader {
+		return nil, fmt.Errorf("invalid magic header: %s", sig.MagicHeader[:])
+	}
+	if _, ok := supportedHashAlgorithms[sig.HashAlgorithm]; !ok {
+		return nil, fmt.Errorf("unsupported hash algorithm: %s", sig.HashAlgorithm)
+	}
+
+	// Now we can unpack the Signature and PublicKey blocks
+	sshSig := ssh.Signature{}
+	if err := ssh.Unmarshal([]byte(sig.Signature), &sshSig); err != nil {
+		return nil, err
+	}
+	// TODO: check the format here (should be rsa-sha512)
+
+	pk, err := ssh.ParsePublicKey([]byte(sig.PublicKey))
+	if err != nil {
+		return nil, err
+	}
+
+	return &Signature{
+		signature: &sshSig,
+		pk:        pk,
+		hashAlg:   sig.HashAlgorithm,
+	}, nil
+}