Validate hostname in uri

API.md

@@ -3068,7 +3068,7 @@ Requires the string value to be a valid [RFC 3986](http://tools.ietf.org/html/rf
     - `allowRelative` - Allow relative URIs. Defaults to `false`.
     - `relativeOnly` - Restrict only relative URIs.  Defaults to `false`.
     - `allowQuerySquareBrackets` - Allows unencoded square brackets inside the query string. This is **NOT** RFC 3986 compliant but query strings like `abc[]=123&abc[]=456` are very common these days. Defaults to `false`.
-    - `domain` - Validate the domain component using the options specified in [`string.domain()`](#stringdomainoptions).
+    - `domain` - Validate the domain component using the options specified in [`string.domain()`](#stringdomainoptions). An extra option `hostname` can be added to validate specific hostnames. It supports a string, a regular expression or an array containing multiples of them.
 
 ```js
 // Accept git or git http/https
@@ -3080,7 +3080,7 @@ const schema = Joi.string().uri({
 });
 ```
 
-Possible validation errors: [`string.uri`](#stringuri), [`string.uriCustomScheme`](#stringuricustomscheme), [`string.uriRelativeOnly`](#stringurirelativeonly), [`string.domain`](#stringdomain)
+Possible validation errors: [`string.uri`](#stringuri), [`string.uriCustomScheme`](#stringuricustomscheme), [`string.uriRelativeOnly`](#stringurirelativeonly), [`string.domain`](#stringdomain), [`string.uri.hostname`](#stringurihostname)
 
 ### `symbol`
 
@@ -4395,6 +4395,10 @@ The string isn't all upper-cased.
 
 The string isn't a valid URI.
 
+#### `string.uri.hostname`
+
+The hostname isn't a match for any of the given hostname strings or regular expressions.
+
 #### `string.uriCustomScheme`
 
 The string isn't a valid URI considering the custom schemes.

lib/types/string.js

@@ -639,7 +639,7 @@ module.exports = Any.extend({
                 Common.assertOptions(options, ['allowRelative', 'allowQuerySquareBrackets', 'domain', 'relativeOnly', 'scheme']);
 
                 if (options.domain) {
-                    Common.assertOptions(options.domain, ['allowFullyQualified', 'allowUnicode', 'maxDomainSegments', 'minDomainSegments', 'tlds']);
+                    Common.assertOptions(options.domain, ['allowFullyQualified', 'allowUnicode', 'maxDomainSegments', 'minDomainSegments', 'tlds', 'hostname']);
                 }
 
                 const { regex, scheme } = Uri.regex(options);
@@ -655,11 +655,40 @@ module.exports = Any.extend({
                 const match = regex.exec(value);
                 if (match) {
                     const matched = match[1] || match[2];
-                    if (domain &&
-                        (!options.allowRelative || matched) &&
-                        !Domain.isValid(matched, domain)) {
 
-                        return helpers.error('string.domain', { value: matched });
+                    if (domain) {
+
+                        if ((!options.allowRelative || matched) &&
+                            !Domain.isValid(matched, domain)) {
+                            return helpers.error('string.domain', { value: matched });
+                        }
+
+                        if (domain.hostname) {
+
+                            const isMatch = (matcher) => {
+
+                                if (matcher instanceof RegExp) {
+                                    return matcher.test(matched);
+                                }
+
+                                return matcher === matched;
+
+                            };
+
+                            if (Array.isArray(domain.hostname)) {
+
+                                if (!domain.hostname.some(isMatch)) {
+                                    return helpers.error('string.uri.hostname', { value: matched, expected: 'any of the hostname items' });
+                                }
+                            }
+                            else {
+
+                                if (!isMatch(domain.hostname)) {
+                                    return helpers.error('string.uri.hostname', { value: matched, expected: domain.hostname });
+                                }
+
+                            }
+                        }
                     }
 
                     return value;
@@ -721,6 +750,7 @@ module.exports = Any.extend({
         'string.pattern.invert.name': '{{#label}} with value {:[.]} matches the inverted {{#name}} pattern',
         'string.trim': '{{#label}} must not have leading or trailing whitespace',
         'string.uri': '{{#label}} must be a valid uri',
+        'string.uri.hostname': '{{#label}} does not match {{#expected}}',
         'string.uriCustomScheme': '{{#label}} must be a valid uri with a scheme matching the {{#scheme}} pattern',
         'string.uriRelativeOnly': '{{#label}} must be a valid relative uri',
         'string.uppercase': '{{#label}} must only contain uppercase characters'

test/types/string.js

@@ -8606,6 +8606,32 @@ describe('string', () => {
 
             expect(() => Joi.string().uri({ foo: 'bar', baz: 'qux' })).to.throw('Options contain unknown keys: foo,baz');
         });
+
+        it('validates domain.hostname', () => {
+
+            const stringSchema = Joi.string().uri({ scheme: 'https', domain: { hostname: 'example.com' } });
+            Helper.validate(stringSchema, [
+                ['https://example.com', true],
+                ['https://example.com/test', true],
+                ['https://test.com', false, '"value" does not match example.com'],
+                ['https://test.com/example', false, '"value" does not match example.com']
+            ]);
+
+            const regexSchema = Joi.string().uri({ scheme: 'https', domain: { hostname: /example.com/ } });
+            Helper.validate(regexSchema, [
+                ['https://example.com', true],
+                ['https://dummy.com', false, '"value" does not match /example.com/']
+            ]);
+
+            const arraySchema = Joi.string().uri({ scheme: 'https', domain: { hostname: ['example.com', 'dummy.org', /dummy.com/] } });
+            Helper.validate(arraySchema, [
+                ['https://example.com/test', true],
+                ['https://test.com/example', false, '"value" does not match any of the hostname items'],
+                ['https://dummy.org/test', true],
+                ['https://dummy.com/test', true]
+            ]);
+
+        });
     });
 
     describe('valid()', () => {