Adds Application certificate path to profile (#10043)

Adds Application certificate path to profile

Prior to this patch, the API Profile type had no way of exposing the
path to an application certificate. While this could be constructed
manually using the `keypaths` package, this was fragile and easy to miss
should the profile layout ever change.

This patch adds `GetAppCertPath()` to the API profile, providing a
centralised and integrated method for finding application
certificates.

api/profile/profile.go

@@ -362,3 +362,10 @@ func (p *Profile) OldSSHCertPath() string {
 func (p *Profile) KnownHostsPath() string {
 	return keypaths.KnownHostsPath(p.Dir)
 }
+
+// AppCertPath returns the path to the profile's certificate for a given
+// application. Note that this function merely constructs the path - there
+// is no guarantee that there is an actual certificate at that location.
+func (p *Profile) AppCertPath(appName string) string {
+	return keypaths.AppCertPath(p.Dir, p.Name(), p.Username, p.SiteName, appName)
+}

api/profile/profile_test.go

@@ -18,7 +18,6 @@ limitations under the License.
 package profile_test
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -34,9 +33,7 @@ import (
 func TestProfileBasics(t *testing.T) {
 	t.Parallel()
 
-	dir, err := ioutil.TempDir("", "teleport")
-	require.NoError(t, err)
-	defer os.RemoveAll(dir)
+	dir := t.TempDir()
 
 	p := &profile.Profile{
 		WebProxyAddr:          "proxy:3088",
@@ -52,7 +49,7 @@ func TestProfileBasics(t *testing.T) {
 	require.Equal(t, "proxy", p.Name())
 
 	// save to a file:
-	err = p.SaveToDir(dir, false)
+	err := p.SaveToDir(dir, false)
 	require.NoError(t, err)
 
 	// verify that the resulting file exists and is of the form `<profile-dir>/<profile-name>.yaml`.
@@ -86,3 +83,20 @@ func TestProfileBasics(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, *p, *clone)
 }
+
+func TestAppPath(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+
+	p := &profile.Profile{
+		WebProxyAddr: "proxy:3088",
+		SSHProxyAddr: "proxy:3023",
+		Username:     "testuser",
+		Dir:          dir,
+		SiteName:     "example.com",
+	}
+
+	expected := filepath.Join(dir, "keys", "proxy", "testuser-app", "example.com", "banana-x509.pem")
+	require.Equal(t, expected, p.AppCertPath("banana"))
+}