feat!: enhance and add feature into digest auth flow #914 (#921)

- redesign the digest auth internals, cleanup, and improvements
- add 'auth-int' QOP support
- add and update digest hash functions
- remove the 'Request.SetDigestAuth' method, keep the option only at the client level

Author: jeevatkm

client.go

@@ -575,33 +575,29 @@ func (c *Client) SetAuthScheme(scheme string) *Client {
 	return c
 }
 
-// SetDigestAuth method sets the Digest Access auth scheme for the client. If a server responds with 401 and sends
-// a Digest challenge in the WWW-Authenticate header, requests will be resent with the appropriate Authorization header.
+// SetDigestAuth method sets the Digest Auth transport with provided credentials in the client.
+// If a server responds with 401 and sends a Digest challenge in the header `WWW-Authenticate`,
+// the request will be resent with the appropriate digest `Authorization` header.
 //
 // For Example: To set the Digest scheme with user "Mufasa" and password "Circle Of Life"
 //
 //	client.SetDigestAuth("Mufasa", "Circle Of Life")
 //
 // Information about Digest Access Authentication can be found in [RFC 7616].
 //
-// See [Request.SetDigestAuth].
+// NOTE:
+//   - On the QOP `auth-int` scenario, the request body is read into memory to
+//     compute the body hash that consumes additional memory usage.
+//   - It is recommended to create a dedicated client instance for digest auth,
+//     as it does digest auth for all the requests raised by the client.
 //
 // [RFC 7616]: https://datatracker.ietf.org/doc/html/rfc7616
 func (c *Client) SetDigestAuth(username, password string) *Client {
-	c.lock.Lock()
-	oldTransport := c.httpClient.Transport
-	c.lock.Unlock()
-	c.AddRequestMiddleware(func(c *Client, _ *Request) error {
-		c.httpClient.Transport = &digestTransport{
-			credentials: credentials{username, password},
-			transport:   oldTransport,
-		}
-		return nil
-	})
-	c.AddResponseMiddleware(func(c *Client, _ *Response) error {
-		c.httpClient.Transport = oldTransport
-		return nil
-	})
+	dt := &digestTransport{
+		credentials: &credentials{username, password},
+		transport:   c.Transport(),
+	}
+	c.SetTransport(dt)
 	return c
 }
 

client_test.go

@@ -90,79 +90,6 @@ func TestClientAuthScheme(t *testing.T) {
 
 }
 
-func TestClientDigestAuth(t *testing.T) {
-	conf := defaultDigestServerConf()
-	ts := createDigestServer(t, conf)
-	defer ts.Close()
-
-	c := dcnl().
-		SetBaseURL(ts.URL+"/").
-		SetDigestAuth(conf.username, conf.password)
-
-	resp, err := c.R().
-		SetResult(&AuthSuccess{}).
-		Get(conf.uri)
-	assertError(t, err)
-	assertEqual(t, http.StatusOK, resp.StatusCode())
-
-	t.Logf("Result Success: %q", resp.Result().(*AuthSuccess))
-	logResponse(t, resp)
-}
-
-func TestClientDigestSession(t *testing.T) {
-	conf := defaultDigestServerConf()
-	conf.algo = "MD5-sess"
-	conf.qop = "auth, auth-int"
-	ts := createDigestServer(t, conf)
-	defer ts.Close()
-
-	c := dcnl().
-		SetBaseURL(ts.URL+"/").
-		SetDigestAuth(conf.username, conf.password)
-
-	resp, err := c.R().
-		SetResult(&AuthSuccess{}).
-		Get(conf.uri)
-	assertError(t, err)
-	assertEqual(t, http.StatusOK, resp.StatusCode())
-
-	t.Logf("Result Success: %q", resp.Result().(*AuthSuccess))
-	logResponse(t, resp)
-}
-
-func TestClientDigestErrors(t *testing.T) {
-	type test struct {
-		mutateConf func(*digestServerConfig)
-		expect     error
-	}
-	tests := []test{
-		{mutateConf: func(c *digestServerConfig) { c.algo = "BAD_ALGO" }, expect: ErrDigestAlgNotSupported},
-		{mutateConf: func(c *digestServerConfig) { c.qop = "bad-qop" }, expect: ErrDigestQopNotSupported},
-		{mutateConf: func(c *digestServerConfig) { c.qop = "" }, expect: ErrDigestNoQop},
-		{mutateConf: func(c *digestServerConfig) { c.charset = "utf-16" }, expect: ErrDigestCharset},
-		{mutateConf: func(c *digestServerConfig) { c.uri = "/bad" }, expect: ErrDigestBadChallenge},
-		{mutateConf: func(c *digestServerConfig) { c.uri = "/unknown_param" }, expect: ErrDigestBadChallenge},
-		{mutateConf: func(c *digestServerConfig) { c.uri = "/missing_value" }, expect: ErrDigestBadChallenge},
-		{mutateConf: func(c *digestServerConfig) { c.uri = "/unclosed_quote" }, expect: ErrDigestBadChallenge},
-		{mutateConf: func(c *digestServerConfig) { c.uri = "/no_challenge" }, expect: ErrDigestBadChallenge},
-		{mutateConf: func(c *digestServerConfig) { c.uri = "/status_500" }, expect: nil},
-	}
-
-	for _, tc := range tests {
-		conf := defaultDigestServerConf()
-		tc.mutateConf(conf)
-		ts := createDigestServer(t, conf)
-
-		c := dcnl().
-			SetBaseURL(ts.URL+"/").
-			SetDigestAuth(conf.username, conf.password)
-
-		_, err := c.R().Get(conf.uri)
-		assertErrorIs(t, tc.expect, err)
-		ts.Close()
-	}
-}
-
 func TestClientResponseMiddleware(t *testing.T) {
 	ts := createGenericServer(t)
 	defer ts.Close()