TUN-8960: Connect to FED API GW based on the OriginCert's endpoint

## Summary

Within the scope of the FEDRamp High RM, it is necessary to detect if an user should connect to a FEDRamp colo.

At first, it was considered to add the --fedramp as global flag however this could be a footgun for the user or even an hindrance, thus, the proposal is to save in the token (during login) if the user authenticated using the FEDRamp Dashboard. This solution makes it easier to the user as they will only be required to pass the flag in login and nothing else.

* Introduces the new field, endpoint, in OriginCert
* Refactors login to remove the private key and certificate which are no longer used
* Login will only store the Argo Tunnel Token
* Remove namedTunnelToken as it was only used to for serialization

Closes TUN-8960

credentials/origin_cert.go

@@ -1,11 +1,13 @@
 package credentials
 
 import (
+	"bytes"
 	"encoding/json"
 	"encoding/pem"
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/mitchellh/go-homedir"
 	"github.com/rs/zerolog"
@@ -17,16 +19,28 @@ const (
 	DefaultCredentialFile = "cert.pem"
 )
 
-type namedTunnelToken struct {
+type OriginCert struct {
 	ZoneID    string `json:"zoneID"`
 	AccountID string `json:"accountID"`
 	APIToken  string `json:"apiToken"`
+	Endpoint  string `json:"endpoint,omitempty"`
 }
 
-type OriginCert struct {
-	ZoneID    string
-	APIToken  string
-	AccountID string
+func (oc *OriginCert) UnmarshalJSON(data []byte) error {
+	var aux struct {
+		ZoneID    string `json:"zoneID"`
+		AccountID string `json:"accountID"`
+		APIToken  string `json:"apiToken"`
+		Endpoint  string `json:"endpoint,omitempty"`
+	}
+	if err := json.Unmarshal(data, &aux); err != nil {
+		return fmt.Errorf("error parsing OriginCert: %v", err)
+	}
+	oc.ZoneID = aux.ZoneID
+	oc.AccountID = aux.AccountID
+	oc.APIToken = aux.APIToken
+	oc.Endpoint = strings.ToLower(aux.Endpoint)
+	return nil
 }
 
 // FindDefaultOriginCertPath returns the first path that contains a cert.pem file. If none of the
@@ -41,40 +55,56 @@ func FindDefaultOriginCertPath() string {
 	return ""
 }
 
+func DecodeOriginCert(blocks []byte) (*OriginCert, error) {
+	return decodeOriginCert(blocks)
+}
+
+func (cert *OriginCert) EncodeOriginCert() ([]byte, error) {
+	if cert == nil {
+		return nil, fmt.Errorf("originCert cannot be nil")
+	}
+	buffer, err := json.Marshal(cert)
+	if err != nil {
+		return nil, fmt.Errorf("originCert marshal failed: %v", err)
+	}
+	block := pem.Block{
+		Type:    "ARGO TUNNEL TOKEN",
+		Headers: map[string]string{},
+		Bytes:   buffer,
+	}
+	var out bytes.Buffer
+	err = pem.Encode(&out, &block)
+	if err != nil {
+		return nil, fmt.Errorf("pem encoding failed: %v", err)
+	}
+	return out.Bytes(), nil
+}
+
 func decodeOriginCert(blocks []byte) (*OriginCert, error) {
 	if len(blocks) == 0 {
-		return nil, fmt.Errorf("Cannot decode empty certificate")
+		return nil, fmt.Errorf("cannot decode empty certificate")
 	}
 	originCert := OriginCert{}
 	block, rest := pem.Decode(blocks)
-	for {
-		if block == nil {
-			break
-		}
+	for block != nil {
 		switch block.Type {
 		case "PRIVATE KEY", "CERTIFICATE":
 			// this is for legacy purposes.
-			break
 		case "ARGO TUNNEL TOKEN":
 			if originCert.ZoneID != "" || originCert.APIToken != "" {
-				return nil, fmt.Errorf("Found multiple tokens in the certificate")
+				return nil, fmt.Errorf("found multiple tokens in the certificate")
 			}
 			// The token is a string,
 			// Try the newer JSON format
-			ntt := namedTunnelToken{}
-			if err := json.Unmarshal(block.Bytes, &ntt); err == nil {
-				originCert.ZoneID = ntt.ZoneID
-				originCert.APIToken = ntt.APIToken
-				originCert.AccountID = ntt.AccountID
-			}
+			_ = json.Unmarshal(block.Bytes, &originCert)
 		default:
-			return nil, fmt.Errorf("Unknown block %s in the certificate", block.Type)
+			return nil, fmt.Errorf("unknown block %s in the certificate", block.Type)
 		}
 		block, rest = pem.Decode(rest)
 	}
 
 	if originCert.ZoneID == "" || originCert.APIToken == "" {
-		return nil, fmt.Errorf("Missing token in the certificate")
+		return nil, fmt.Errorf("missing token in the certificate")
 	}
 
 	return &originCert, nil