libgit2: change credentialsCallback logic

This changes the logic of `credentialsCallback` so that it takes the
`allowedTypes` passed on by `git2go` into account. Reason for this
change is because this prepares it to work with `v33`, but also
because it can provide better guidance when `libgit2` has been
compiled with a different configuration, which e.g. doesn't
allow for "in-memory SSH keys".

Because `AuthOptions#Identity` now gets validated by the callback
and go-git does its own validaiton, the check has been removed
from `Validate` (and now does a simple check if the fields are set).

Signed-off-by: Hidde Beydals <hello@hidde.co>

pkg/git/libgit2/transport.go

@@ -23,6 +23,7 @@ import (
 	"crypto/sha1"
 	"crypto/sha256"
 	"crypto/x509"
+	"fmt"
 	"hash"
 	"net"
 	"strings"
@@ -52,29 +53,32 @@ func RemoteCallbacks(opts *git.AuthOptions) git2go.RemoteCallbacks {
 }
 
 // credentialsCallback constructs CredentialsCallbacks with the given options
-// for git.Transport if the given opts is not nil, and returns the result.
+// for git.Transport, and returns the result.
 func credentialsCallback(opts *git.AuthOptions) git2go.CredentialsCallback {
-	switch opts.Transport {
-	case git.HTTP:
-		if opts.Username != "" {
-			return func(u string, user string, allowedTypes git2go.CredentialType) (*git2go.Credential, error) {
-				return git2go.NewCredentialUsername(opts.Username)
+	return func(url string, username string, allowedTypes git2go.CredentialType) (*git2go.Credential, error) {
+		if allowedTypes & (git2go.CredentialTypeSSHKey|git2go.CredentialTypeSSHCustom|git2go.CredentialTypeSSHMemory) != 0 {
+			var (
+				signer ssh.Signer
+				err error
+			)
+			if opts.Password != "" {
+				signer, err = ssh.ParsePrivateKeyWithPassphrase(opts.Identity, []byte(opts.Password))
+			} else {
+				signer, err = ssh.ParsePrivateKey(opts.Identity)
 			}
-		}
-	case git.HTTPS:
-		if opts.Username != "" && opts.Password != "" {
-			return func(u string, user string, allowedTypes git2go.CredentialType) (*git2go.Credential, error) {
-				return git2go.NewCredentialUserpassPlaintext(opts.Username, opts.Password)
+			if err != nil {
+				return nil, err
 			}
+			return git2go.NewCredentialSSHKeyFromSigner(opts.Username, signer)
 		}
-	case git.SSH:
-		if len(opts.Identity) > 0 {
-			return func(u string, user string, allowedTypes git2go.CredentialType) (*git2go.Credential, error) {
-				return git2go.NewCredentialSSHKeyFromMemory(opts.Username, "", string(opts.Identity), opts.Password)
-			}
+		if (allowedTypes & git2go.CredentialTypeUserpassPlaintext) != 0 {
+			return git2go.NewCredentialUserpassPlaintext(opts.Username, opts.Password)
 		}
+		if (allowedTypes & git2go.CredentialTypeUsername) != 0 {
+			return git2go.NewCredentialUsername(opts.Username)
+		}
+		return nil, fmt.Errorf("unknown credential type %+v", allowedTypes)
 	}
-	return nil
 }
 
 // certificateCallback constructs CertificateCallback with the given options

pkg/git/options.go

@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"net/url"
 
-	"golang.org/x/crypto/ssh"
 	v1 "k8s.io/api/core/v1"
 )
 
@@ -82,15 +81,6 @@ func (o AuthOptions) Validate() error {
 		if len(o.Identity) == 0 {
 			return fmt.Errorf("invalid '%s' auth option: 'identity' is required", o.Transport)
 		}
-		var err error
-		if o.Password != "" {
-			_, err = ssh.ParsePrivateKeyWithPassphrase(o.Identity, []byte(o.Password))
-		} else {
-			_, err = ssh.ParsePrivateKey(o.Identity)
-		}
-		if err != nil {
-			return fmt.Errorf("invalid '%s' auth option 'identity': %w", o.Transport, err)
-		}
 		if len(o.KnownHosts) == 0 {
 			return fmt.Errorf("invalid '%s' auth option: 'known_hosts' is required", o.Transport)
 		}