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package sasquatch
import (
"bufio"
"bytes"
"crypto/ed25519"
"crypto/rsa"
"errors"
"fmt"
"io"
"io/ioutil"
"os"
"strings"
"golang.org/x/crypto/ssh"
)
// An Identity is a private key or other value that can decrypt an opaque file
// key from a recipient stanza.
//
// Unwrap must return ErrIncorrectIdentity for recipient blocks that don't match
// the identity, any other error might be considered fatal.
type Identity interface {
Type() string
Unwrap(block *Stanza) (fileKey []byte, err error)
}
// IdentityMatcher can be optionally implemented by an Identity that can
// communicate whether it can decrypt a recipient stanza without decrypting it.
//
// If an Identity implements IdentityMatcher, its Unwrap method will only be
// invoked on blocks for which Match returned nil. Match must return
// ErrIncorrectIdentity for recipient blocks that don't match the identity, any
// other error might be considered fatal.
type IdentityMatcher interface {
Identity
Match(block *Stanza) error
}
var ErrIncorrectIdentity = errors.New("incorrect identity for recipient block")
// FindIdentities returns all available identities.
func FindIdentities() []Identity {
// from disk
keys, err := FindSSHKeys()
if err != nil {
return nil
}
ids := []Identity{}
for _, key := range keys {
// fmt.Println("parsing", key)
i, err := ParseIdentitiesFile(key)
if err != nil {
// fmt.Println(err)
continue
}
ids = append(ids, i...)
}
// from agent
signers, err := SSHAgentSigners()
if err != nil {
return ids
}
for _, signer := range signers {
i, err := NewChallengeIdentity(signer)
if err != nil {
continue
}
ids = append(ids, i)
}
return ids
}
const privateKeySizeLimit = 1 << 24 // 16 MiB
// ParseIdentitiesFile retrieves all identities found in a private key.
func ParseIdentitiesFile(name string) ([]Identity, error) {
f, err := os.Open(name)
if err != nil {
return nil, fmt.Errorf("failed to open file: %v", err)
}
defer f.Close()
contents, err := ioutil.ReadAll(io.LimitReader(f, privateKeySizeLimit))
if err != nil {
return nil, fmt.Errorf("failed to read %q: %v", name, err)
}
if len(contents) == privateKeySizeLimit {
return nil, fmt.Errorf("failed to read %q: file too long", name)
}
var ids []Identity
scanner := bufio.NewScanner(bytes.NewReader(contents))
for scanner.Scan() {
line := scanner.Text()
if strings.HasPrefix(line, "#") || line == "" {
continue
}
if strings.HasPrefix(line, "-----BEGIN") {
return parseSSHIdentity(name, contents)
}
}
if err := scanner.Err(); err != nil {
return nil, fmt.Errorf("failed to read %q: %v", name, err)
}
if len(ids) == 0 {
return nil, fmt.Errorf("no secret keys found in %q", name)
}
return ids, nil
}
func parseIdentity(pemBytes []byte) (Identity, error) {
k, err := ssh.ParseRawPrivateKey(pemBytes)
if err != nil {
return nil, err
}
switch k := k.(type) {
case ed25519.PrivateKey:
return NewEd25519Identity(k)
case *ed25519.PrivateKey:
return NewEd25519Identity(*k)
case rsa.PrivateKey:
return NewRSAIdentity(&k)
case *rsa.PrivateKey:
return NewRSAIdentity(k)
}
return nil, fmt.Errorf("unsupported SSH identity type: %T", k)
}
func parseSSHIdentity(name string, pemBytes []byte) ([]Identity, error) {
id, err := parseIdentity(pemBytes)
if sshErr, ok := err.(*ssh.PassphraseMissingError); ok {
pubKey := sshErr.PublicKey
if pubKey == nil {
pubKey, err = readPubFile(name)
if err != nil {
return nil, err
}
}
passphrasePrompt := func() ([]byte, error) {
fmt.Fprintf(os.Stderr, "Enter passphrase for %q: ", name)
pass, err := readPassphrase()
if err != nil {
return nil, fmt.Errorf("could not read passphrase for %q: %v", name, err)
}
return pass, nil
}
i, err := NewEncryptedSSHIdentity(pubKey, pemBytes, passphrasePrompt)
if err != nil {
return nil, err
}
return []Identity{i}, nil
}
if err != nil {
return nil, fmt.Errorf("malformed SSH identity in %q: %v", name, err)
}
return []Identity{id}, nil
}
func readPubFile(name string) (ssh.PublicKey, error) {
f, err := os.Open(name + ".pub")
if err != nil {
return nil, fmt.Errorf(`failed to obtain public key for %q SSH key: %v
Ensure %q exists, or convert the private key %q to a modern format with "ssh-keygen -p -m RFC4716"`, name, err, name+".pub", name)
}
defer f.Close()
contents, err := ioutil.ReadAll(f)
if err != nil {
return nil, fmt.Errorf("failed to read %q: %v", name+".pub", err)
}
pubKey, _, _, _, err := ssh.ParseAuthorizedKey(contents)
if err != nil {
return nil, fmt.Errorf("failed to parse %q: %v", name+".pub", err)
}
return pubKey, nil
}
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