Extend further validation of config values (#8469)

- This PR allows config KVS to be validated properly
  without being affected by ENV overrides, rejects
  invalid values during set operation

- Expands unit tests and refactors the error handling
  for notification targets, returns error instead of
  ignoring targets for invalid KVS

- Does all the prep-work for implementing safe-mode
  style operation for MinIO server, introduces a new
  global variable to toggle safe mode based operations
  NOTE: this PR itself doesn't provide safe mode operations

pkg/env/env.go

@@ -3,26 +3,47 @@ package env
 import (
 	"os"
 	"strings"
+	"sync"
 )
 
+var (
+	privateMutex sync.RWMutex
+	envOff       bool
+)
+
+// SetEnvOff - turns off env lookup
+func SetEnvOff() {
+	privateMutex.Lock()
+	defer privateMutex.Unlock()
+
+	envOff = true
+}
+
+// SetEnvOn - turns on env lookup
+func SetEnvOn() {
+	privateMutex.Lock()
+	defer privateMutex.Unlock()
+
+	envOff = false
+}
+
 // Get retrieves the value of the environment variable named
 // by the key. If the variable is present in the environment the
 // value (which may be empty) is returned. Otherwise it returns
 // the specified default value.
 func Get(key, defaultValue string) string {
+	privateMutex.RLock()
+	ok := envOff
+	privateMutex.RUnlock()
+	if ok {
+		return defaultValue
+	}
 	if v, ok := os.LookupEnv(key); ok {
 		return v
 	}
 	return defaultValue
 }
 
-// Lookup retrieves the value of the environment variable named
-// by the key. If the variable is present in the environment the
-// value (which may be empty) is returned and the boolean is true.
-// Otherwise the returned value will be empty and the boolean will
-// be false.
-func Lookup(key string) (string, bool) { return os.LookupEnv(key) }
-
 // List all envs with a given prefix.
 func List(prefix string) (envs []string) {
 	for _, env := range os.Environ() {

pkg/event/target/webhook.go

@@ -98,7 +98,7 @@ func (target *WebhookTarget) Save(eventData event.Event) error {
 	if target.store != nil {
 		return target.store.Put(eventData)
 	}
-	u, pErr := xnet.ParseURL(target.args.Endpoint.String())
+	u, pErr := xnet.ParseHTTPURL(target.args.Endpoint.String())
 	if pErr != nil {
 		return pErr
 	}
@@ -153,7 +153,7 @@ func (target *WebhookTarget) send(eventData event.Event) error {
 
 // Send - reads an event from store and sends it to webhook.
 func (target *WebhookTarget) Send(eventKey string) error {
-	u, pErr := xnet.ParseURL(target.args.Endpoint.String())
+	u, pErr := xnet.ParseHTTPURL(target.args.Endpoint.String())
 	if pErr != nil {
 		return pErr
 	}

pkg/net/url.go

@@ -19,6 +19,7 @@ package net
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"net"
 	"net/http"
 	"net/url"
@@ -103,6 +104,21 @@ func (u URL) DialHTTP() error {
 	return nil
 }
 
+// ParseHTTPURL - parses a string into HTTP URL, string is
+// expected to be of form http:// or https://
+func ParseHTTPURL(s string) (u *URL, err error) {
+	u, err = ParseURL(s)
+	if err != nil {
+		return nil, err
+	}
+	switch u.Scheme {
+	default:
+		return nil, fmt.Errorf("unexpected scheme found %s", u.Scheme)
+	case "http", "https":
+		return u, nil
+	}
+}
+
 // ParseURL - parses string into URL.
 func ParseURL(s string) (u *URL, err error) {
 	var uu *url.URL

pkg/net/url_test.go

@@ -133,6 +133,42 @@ func TestURLUnmarshalJSON(t *testing.T) {
 	}
 }
 
+func TestParseHTTPURL(t *testing.T) {
+	testCases := []struct {
+		s           string
+		expectedURL *URL
+		expectErr   bool
+	}{
+		{"http://play", &URL{Scheme: "http", Host: "play"}, false},
+		{"https://play.min.io:0", &URL{Scheme: "https", Host: "play.min.io:0"}, false},
+		{"https://147.75.201.93:9000/", &URL{Scheme: "https", Host: "147.75.201.93:9000", Path: "/"}, false},
+		{"https://s3.amazonaws.com/?location", &URL{Scheme: "https", Host: "s3.amazonaws.com", Path: "/", RawQuery: "location"}, false},
+		{"http://myminio:10000/mybucket//myobject/", &URL{Scheme: "http", Host: "myminio:10000", Path: "/mybucket/myobject/"}, false},
+		{"ftp://myftp.server:10000/myuser", nil, true},
+		{"https://my.server:10000000/myuser", nil, true},
+		{"myserver:1000", nil, true},
+		{"http://:1000/mybucket", nil, true},
+		{"https://147.75.201.93:90000/", nil, true},
+		{"http:/play", nil, true},
+	}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+		t.Run(testCase.s, func(t *testing.T) {
+			url, err := ParseHTTPURL(testCase.s)
+			expectErr := (err != nil)
+			if expectErr != testCase.expectErr {
+				t.Fatalf("error: expected: %v, got: %v", testCase.expectErr, expectErr)
+			}
+			if !testCase.expectErr {
+				if !reflect.DeepEqual(url, testCase.expectedURL) {
+					t.Fatalf("host: expected: %#v, got: %#v", testCase.expectedURL, url)
+				}
+			}
+		})
+	}
+}
+
 func TestParseURL(t *testing.T) {
 	testCases := []struct {
 		s           string