add support for auth-snippet annotation

add test for new auth-snippet annotation

document auth-snippet annotation

add e2e test for auth-snippet annotation

add log warning and update documentation

docs/user-guide/nginx-configuration/annotations.md

@@ -27,6 +27,7 @@ You can add these Kubernetes annotations to specific Ingress objects to customiz
 |[nginx.ingress.kubernetes.io/auth-tls-error-page](#client-certificate-authentication)|string|
 |[nginx.ingress.kubernetes.io/auth-tls-pass-certificate-to-upstream](#client-certificate-authentication)|"true" or "false"|
 |[nginx.ingress.kubernetes.io/auth-url](#external-authentication)|string|
+|[nginx.ingress.kubernetes.io/auth-snippet](#external-authentication)|string|
 |[nginx.ingress.kubernetes.io/backend-protocol](#backend-protocol)|string|HTTP,HTTPS,GRPC,GRPCS,AJP|
 |[nginx.ingress.kubernetes.io/base-url-scheme](#rewrite)|string|
 |[nginx.ingress.kubernetes.io/client-body-buffer-size](#client-body-buffer-size)|string|
@@ -326,6 +327,15 @@ Additionally it is possible to set:
   `<Response_Header_1, ..., Response_Header_n>` to specify headers to pass to backend once authentication request completes.
 * `nginx.ingress.kubernetes.io/auth-request-redirect`:
   `<Request_Redirect_URL>`  to specify the X-Auth-Request-Redirect header value.
+* `nginx.ingress.kubernetes.io/auth-snippet`:
+  `<Auth_Snippet>` to specify a custom snippet to use with external authentication, e.g.
+
+```yaml
+nginx.ingress.kubernetes.io/auth-url: http://foo.com/external-auth
+nginx.ingress.kubernetes.io/auth-snippet: |
+    proxy_set_header Foo-Header 42;
+```
+> Note: `nginx.ingress.kubernetes.io/auth-snippet` is an optional annotation. However, it may only be used in conjunction with `nginx.ingress.kubernetes.io/auth-url` and will be ignored if `nginx.ingress.kubernetes.io/auth-url` is not set
 
 !!! example
     Please check the [external-auth](../../examples/auth/external-auth/README.md) example.

internal/ingress/annotations/authreq/main.go

@@ -21,6 +21,8 @@ import (
 	"regexp"
 	"strings"
 
+	"github.com/golang/glog"
+
 	extensions "k8s.io/api/extensions/v1beta1"
 
 	"k8s.io/ingress-nginx/internal/ingress/annotations/parser"
@@ -37,6 +39,7 @@ type Config struct {
 	Method          string   `json:"method"`
 	ResponseHeaders []string `json:"responseHeaders,omitempty"`
 	RequestRedirect string   `json:"requestRedirect"`
+	AuthSnippet     string   `json:"authSnippet"`
 }
 
 // Equal tests for equality between two Config types
@@ -74,6 +77,9 @@ func (e1 *Config) Equal(e2 *Config) bool {
 	if e1.RequestRedirect != e2.RequestRedirect {
 		return false
 	}
+	if e1.AuthSnippet != e2.AuthSnippet {
+		return false
+	}
 
 	return true
 }
@@ -141,7 +147,15 @@ func (a authReq) Parse(ing *extensions.Ingress) (interface{}, error) {
 	}
 
 	// Optional Parameters
-	signIn, _ := parser.GetStringAnnotation("auth-signin", ing)
+	signIn, err := parser.GetStringAnnotation("auth-signin", ing)
+	if err != nil {
+		glog.Warning("auth-signin annotation is undefined and will not be set")
+	}
+
+	authSnippet, err := parser.GetStringAnnotation("auth-snippet", ing)
+	if err != nil {
+		glog.Warning("auth-snippet annotation is undefined and will not be set")
+	}
 
 	responseHeaders := []string{}
 	hstr, _ := parser.GetStringAnnotation("auth-response-headers", ing)
@@ -167,5 +181,6 @@ func (a authReq) Parse(ing *extensions.Ingress) (interface{}, error) {
 		Method:          authMethod,
 		ResponseHeaders: responseHeaders,
 		RequestRedirect: requestRedirect,
+		AuthSnippet:     authSnippet,
 	}, nil
 }

internal/ingress/annotations/authreq/main_test.go

@@ -77,16 +77,18 @@ func TestAnnotations(t *testing.T) {
 		signinURL       string
 		method          string
 		requestRedirect string
+		authSnippet     string
 		expErr          bool
 	}{
-		{"empty", "", "", "", "", true},
-		{"no scheme", "bar", "bar", "", "", true},
-		{"invalid host", "http://", "http://", "", "", true},
-		{"invalid host (multiple dots)", "http://foo..bar.com", "http://foo..bar.com", "", "", true},
-		{"valid URL", "http://bar.foo.com/external-auth", "http://bar.foo.com/external-auth", "", "", false},
-		{"valid URL - send body", "http://foo.com/external-auth", "http://foo.com/external-auth", "POST", "", false},
-		{"valid URL - send body", "http://foo.com/external-auth", "http://foo.com/external-auth", "GET", "", false},
-		{"valid URL - request redirect", "http://foo.com/external-auth", "http://foo.com/external-auth", "GET", "http://foo.com/redirect-me", false},
+		{"empty", "", "", "", "", "", true},
+		{"no scheme", "bar", "bar", "", "", "", true},
+		{"invalid host", "http://", "http://", "", "", "", true},
+		{"invalid host (multiple dots)", "http://foo..bar.com", "http://foo..bar.com", "", "", "", true},
+		{"valid URL", "http://bar.foo.com/external-auth", "http://bar.foo.com/external-auth", "", "", "", false},
+		{"valid URL - send body", "http://foo.com/external-auth", "http://foo.com/external-auth", "POST", "", "", false},
+		{"valid URL - send body", "http://foo.com/external-auth", "http://foo.com/external-auth", "GET", "", "", false},
+		{"valid URL - request redirect", "http://foo.com/external-auth", "http://foo.com/external-auth", "GET", "http://foo.com/redirect-me", "", false},
+		{"auth snippet", "http://foo.com/external-auth", "http://foo.com/external-auth", "", "", "proxy_set_header My-Custom-Header 42;", false},
 	}
 
 	for _, test := range tests {
@@ -94,11 +96,12 @@ func TestAnnotations(t *testing.T) {
 		data[parser.GetAnnotationWithPrefix("auth-signin")] = test.signinURL
 		data[parser.GetAnnotationWithPrefix("auth-method")] = fmt.Sprintf("%v", test.method)
 		data[parser.GetAnnotationWithPrefix("auth-request-redirect")] = test.requestRedirect
+		data[parser.GetAnnotationWithPrefix("auth-snippet")] = test.authSnippet
 
 		i, err := NewParser(&resolver.Mock{}).Parse(ing)
 		if test.expErr {
 			if err == nil {
-				t.Errorf("%v: expected error but retuned nil", test.title)
+				t.Errorf("%v: expected error but returned nil", test.title)
 			}
 			continue
 		}
@@ -118,6 +121,9 @@ func TestAnnotations(t *testing.T) {
 		if u.RequestRedirect != test.requestRedirect {
 			t.Errorf("%v: expected \"%v\" but \"%v\" was returned", test.title, test.requestRedirect, u.RequestRedirect)
 		}
+		if u.AuthSnippet != test.authSnippet {
+			t.Errorf("%v: expected \"%v\" but \"%v\" was returned", test.title, test.authSnippet, u.AuthSnippet)
+		}
 	}
 }
 

rootfs/etc/nginx/template/nginx.tmpl

@@ -888,6 +888,10 @@ stream {
             proxy_set_header ssl-client-issuer-dn   $ssl_client_i_dn;
             {{ end }}
 
+            {{ if not (empty $location.ExternalAuth.AuthSnippet) }}
+            {{ $location.ExternalAuth.AuthSnippet }}
+            {{ end }}
+
             set $target {{ $location.ExternalAuth.URL }};
             proxy_pass $target;
         }

test/e2e/annotations/auth.go

@@ -25,7 +25,6 @@ import (
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
 	"github.com/parnurzeal/gorequest"
 
 	corev1 "k8s.io/api/core/v1"
@@ -234,6 +233,41 @@ var _ = framework.IngressNginxDescribe("Annotations - Auth", func() {
 		Expect(resp.StatusCode).Should(Equal(http.StatusInternalServerError))
 	})
 
+	It(`should set snippet "proxy_set_header My-Custom-Header 42;" when external auth is configured`, func() {
+		host := "auth"
+
+		annotations := map[string]string{
+			"nginx.ingress.kubernetes.io/auth-url": "http://foo.bar/basic-auth/user/password",
+			"nginx.ingress.kubernetes.io/auth-snippet": `
+				proxy_set_header My-Custom-Header 42;`,
+		}
+
+		ing := framework.NewSingleIngress(host, "/", host, f.IngressController.Namespace, "http-svc", 80, &annotations)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return Expect(server).Should(ContainSubstring(`proxy_set_header My-Custom-Header 42;`))
+			})
+	})
+
+	It(`should not set snippet "proxy_set_header My-Custom-Header 42;" when external auth is not configured`, func() {
+		host := "auth"
+
+		annotations := map[string]string{
+			"nginx.ingress.kubernetes.io/auth-snippet": `
+				proxy_set_header My-Custom-Header 42;`,
+		}
+
+		ing := framework.NewSingleIngress(host, "/", host, f.IngressController.Namespace, "http-svc", 80, &annotations)
+		f.EnsureIngress(ing)
+
+		f.WaitForNginxServer(host,
+			func(server string) bool {
+				return Expect(server).ShouldNot(ContainSubstring(`proxy_set_header My-Custom-Header 42;`))
+			})
+	})
+
 	Context("when external authentication is configured", func() {
 		host := "auth"