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package sshutil
import (
"crypto"
"crypto/dsa" //nolint:staticcheck // support for DSA fingerprints
"crypto/ecdh"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/elliptic"
"crypto/rsa"
"fmt"
"math/big"
"golang.org/x/crypto/ssh"
"golang.org/x/crypto/ssh/agent"
)
// CryptoPublicKey returns the crypto.PublicKey version of an ssh.PublicKey or
// *agent.Key.
func CryptoPublicKey(pub interface{}) (crypto.PublicKey, error) {
switch p := pub.(type) {
case *ecdsa.PublicKey, *rsa.PublicKey, ed25519.PublicKey, *dsa.PublicKey:
return pub, nil
case ssh.CryptoPublicKey:
return p.CryptoPublicKey(), nil
case *agent.Key:
sshPub, err := ssh.ParsePublicKey(p.Blob)
if err != nil {
return nil, err
}
return CryptoPublicKey(sshPub)
case ssh.PublicKey:
// sk keys do not implement ssh.CryptoPublicKey
return cryptoSKPublicKey(p)
default:
return nil, fmt.Errorf("unsupported public key type %T", pub)
}
}
// cryptoSKPublicKey returns the crypto.PublicKey of an SSH SK public keys.
func cryptoSKPublicKey(pub ssh.PublicKey) (crypto.PublicKey, error) {
switch pub.Type() {
case "sk-ecdsa-sha2-nistp256@openssh.com":
var w struct {
Name string
ID string
Key []byte
Application string
}
if err := ssh.Unmarshal(pub.Marshal(), &w); err != nil {
return nil, err
}
p, err := ecdh.P256().NewPublicKey(w.Key)
if err != nil {
return nil, fmt.Errorf("failed decoding ECDSA key: %w", err)
}
return &ecdsa.PublicKey{
Curve: elliptic.P256(),
X: big.NewInt(0).SetBytes(p.Bytes()[1:33]),
Y: big.NewInt(0).SetBytes(p.Bytes()[33:]),
}, nil
case "sk-ssh-ed25519@openssh.com":
var w struct {
Name string
KeyBytes []byte
Application string
}
if err := ssh.Unmarshal(pub.Marshal(), &w); err != nil {
return nil, err
}
if l := len(w.KeyBytes); l != ed25519.PublicKeySize {
return nil, fmt.Errorf("invalid size %d for Ed25519 public key", l)
}
return ed25519.PublicKey(w.KeyBytes), nil
default:
return nil, fmt.Errorf("unsupported public key type %s", pub.Type())
}
}
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