Fix ed25519 generated SSH key marshalling (#14101)

* Ensure we can issue against generated SSH CA keys

This adds a test to ensure that we can issue leaf SSH certificates using
the newly generated SSH CA keys. Presently this fails because the
ed25519 key private is stored using PKIX's PKCS8 PrivateKey object
format rather than using OpenSSH's desired private key format:

> path_config_ca_test.go:211: bad case 12: err: failed to parse stored CA private key: ssh: invalid openssh private key format, resp: <nil>

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

* Add dependency on edkey for OpenSSH ed25519 keys

As mentioned in various terraform-provider-tls discussions, OpenSSH
doesn't understand the standard OpenSSL/PKIX ed25519 key structure (as
generated by PKCS8 marshalling). Instead, we need to place it into the
OpenSSH RFC 8709 format. As mentioned in this dependency's README,
support in golang.org/x/crypto/ssh is presently lacking for this.
When the associated CL is merged, we should be able to remove this dep
and rely on the (extended) standard library, however, no review progress
appears to have been made since the CL was opened by the author.

See also: https://go-review.googlesource.com/c/crypto/+/218620/

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

builtin/logical/ssh/path_config_ca.go

@@ -10,6 +10,7 @@ import (
 	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"io"
 
@@ -17,6 +18,8 @@ import (
 	"github.com/hashicorp/vault/sdk/framework"
 	"github.com/hashicorp/vault/sdk/logical"
 	"golang.org/x/crypto/ssh"
+
+	"github.com/mikesmitty/edkey"
 )
 
 const (
@@ -357,9 +360,9 @@ func generateSSHKeyPair(randomSource io.Reader, keyType string, keyBits int) (st
 			return "", "", err
 		}
 
-		marshalled, err := x509.MarshalPKCS8PrivateKey(privateSeed)
-		if err != nil {
-			return "", "", err
+		marshalled := edkey.MarshalED25519PrivateKey(privateSeed)
+		if marshalled == nil {
+			return "", "", errors.New("unable to marshal ed25519 private key")
 		}
 
 		privateBlock = &pem.Block{

builtin/logical/ssh/path_config_ca_test.go

@@ -191,17 +191,31 @@ func createDeleteHelper(t *testing.T, b logical.Backend, config *logical.Backend
 	}
 	resp, err := b.HandleRequest(context.Background(), caReq)
 	if err != nil || (resp != nil && resp.IsError()) {
-		t.Fatalf("bad case %v: err: %v, resp:%v", index, err, resp)
+		t.Fatalf("bad case %v: err: %v, resp: %v", index, err, resp)
 	}
 	if !strings.Contains(resp.Data["public_key"].(string), caReq.Data["key_type"].(string)) {
 		t.Fatalf("bad case %v: expected public key of type %v but was %v", index, caReq.Data["key_type"], resp.Data["public_key"])
 	}
 
+	issueOptions := map[string]interface{}{
+		"public_key": testCAPublicKeyEd25519,
+	}
+	issueReq := &logical.Request{
+		Path:      "sign/ca-issuance",
+		Operation: logical.UpdateOperation,
+		Storage:   config.StorageView,
+		Data:      issueOptions,
+	}
+	resp, err = b.HandleRequest(context.Background(), issueReq)
+	if err != nil || (resp != nil && resp.IsError()) {
+		t.Fatalf("bad case %v: err: %v, resp: %v", index, err, resp)
+	}
+
 	// Delete the configured keys
 	caReq.Operation = logical.DeleteOperation
 	resp, err = b.HandleRequest(context.Background(), caReq)
 	if err != nil || (resp != nil && resp.IsError()) {
-		t.Fatalf("bad case %v: err: %v, resp:%v", index, err, resp)
+		t.Fatalf("bad case %v: err: %v, resp: %v", index, err, resp)
 	}
 }
 
@@ -235,6 +249,24 @@ func TestSSH_ConfigCAKeyTypes(t *testing.T) {
 		{"ed25519", 0},
 	}
 
+	// Create a role for ssh signing.
+	roleOptions := map[string]interface{}{
+		"allow_user_certificates": true,
+		"allowed_users":           "*",
+		"key_type":                "ca",
+		"ttl":                     "30s",
+	}
+	roleReq := &logical.Request{
+		Operation: logical.UpdateOperation,
+		Path:      "roles/ca-issuance",
+		Data:      roleOptions,
+		Storage:   config.StorageView,
+	}
+	_, err = b.HandleRequest(context.Background(), roleReq)
+	if err != nil {
+		t.Fatalf("Cannot create role to issue against: %s", err)
+	}
+
 	for index, scenario := range cases {
 		createDeleteHelper(t, b, config, index, scenario.keyType, scenario.keyBits)
 	}

go.mod

@@ -306,6 +306,7 @@ require (
 	github.com/mattn/go-isatty v0.0.14 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.2-0.20181231171920-c182affec369 // indirect
 	github.com/miekg/dns v1.1.41 // indirect
+	github.com/mikesmitty/edkey v0.0.0-20170222072505-3356ea4e686a // indirect
 	github.com/mitchellh/hashstructure v1.0.0 // indirect
 	github.com/mitchellh/iochan v1.0.0 // indirect
 	github.com/mitchellh/pointerstructure v1.2.0 // indirect

go.sum

@@ -1160,6 +1160,8 @@ github.com/miekg/dns v1.1.40/go.mod h1:KNUDUusw/aVsxyTYZM1oqvCicbwhgbNgztCETuNZ7
 github.com/miekg/dns v1.1.41 h1:WMszZWJG0XmzbK9FEmzH2TVcqYzFesusSIB41b8KHxY=
 github.com/miekg/dns v1.1.41/go.mod h1:p6aan82bvRIyn+zDIv9xYNUpwa73JcSh9BKwknJysuI=
 github.com/miekg/pkcs11 v1.0.3/go.mod h1:XsNlhZGX73bx86s2hdc/FuaLm2CPZJemRLMA+WTFxgs=
+github.com/mikesmitty/edkey v0.0.0-20170222072505-3356ea4e686a h1:eU8j/ClY2Ty3qdHnn0TyW3ivFoPC/0F1gQZz8yTxbbE=
+github.com/mikesmitty/edkey v0.0.0-20170222072505-3356ea4e686a/go.mod h1:v8eSC2SMp9/7FTKUncp7fH9IwPfw+ysMObcEz5FWheQ=
 github.com/mistifyio/go-zfs v2.1.2-0.20190413222219-f784269be439+incompatible/go.mod h1:8AuVvqP/mXw1px98n46wfvcGfQ4ci2FwoAjKYxuo3Z4=
 github.com/mitchellh/cli v1.0.0/go.mod h1:hNIlj7HEI86fIcpObd7a0FcrxTWetlwJDGcceTlRvqc=
 github.com/mitchellh/cli v1.1.0/go.mod h1:xcISNoH86gajksDmfB23e/pu+B+GeFRMYmoHXxx3xhI=