96 lines
2.4 KiB
Go
96 lines
2.4 KiB
Go
// Modified by 42wim
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//
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// Copyright 2021 The Sigstore Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package sshsig
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import (
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"errors"
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"fmt"
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"github.com/42wim/sshsig/pem"
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"golang.org/x/crypto/ssh"
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)
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const (
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pemType = "SSH SIGNATURE"
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)
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// Armored returns the signature in an armored format.
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func Armor(s *ssh.Signature, p ssh.PublicKey, ns string) []byte {
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sig := WrappedSig{
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Version: 1,
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PublicKey: string(p.Marshal()),
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Namespace: ns,
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HashAlgorithm: defaultHashAlgorithm,
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Signature: string(ssh.Marshal(s)),
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}
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copy(sig.MagicHeader[:], magicHeader)
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enc := pem.EncodeToMemory(&pem.Block{
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Type: pemType,
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Bytes: ssh.Marshal(sig),
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})
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return enc
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}
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// Decode parses an armored signature.
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func Decode(b []byte) (*Signature, error) {
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pemBlock, _ := pem.Decode(b)
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if pemBlock == nil {
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return nil, errors.New("unable to decode pem file")
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}
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if pemBlock.Type != pemType {
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return nil, fmt.Errorf("wrong pem block type: %s. Expected SSH-SIGNATURE", pemBlock.Type)
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}
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// Now we unmarshal it into the Signature block
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sig := WrappedSig{}
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if err := ssh.Unmarshal(pemBlock.Bytes, &sig); err != nil {
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return nil, err
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}
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if sig.Version != 1 {
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return nil, fmt.Errorf("unsupported signature version: %d", sig.Version)
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}
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if string(sig.MagicHeader[:]) != magicHeader {
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return nil, fmt.Errorf("invalid magic header: %s", sig.MagicHeader[:])
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}
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if _, ok := supportedHashAlgorithms[sig.HashAlgorithm]; !ok {
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return nil, fmt.Errorf("unsupported hash algorithm: %s", sig.HashAlgorithm)
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}
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// Now we can unpack the Signature and PublicKey blocks
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sshSig := ssh.Signature{}
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if err := ssh.Unmarshal([]byte(sig.Signature), &sshSig); err != nil {
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return nil, err
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}
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// TODO: check the format here (should be rsa-sha512)
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pk, err := ssh.ParsePublicKey([]byte(sig.PublicKey))
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if err != nil {
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return nil, err
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}
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return &Signature{
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signature: &sshSig,
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pk: pk,
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hashAlg: sig.HashAlgorithm,
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}, nil
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}
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