[12.x] Add encoding validation rule for uploaded files

src/Illuminate/Translation/lang/en/validation.php

@@ -52,6 +52,7 @@
     'doesnt_end_with' => 'The :attribute field must not end with one of the following: :values.',
     'doesnt_start_with' => 'The :attribute field must not start with one of the following: :values.',
     'email' => 'The :attribute field must be a valid email address.',
+    'encoding' => 'The :attribute field must encoded in :encoding.',
     'ends_with' => 'The :attribute field must end with one of the following: :values.',
     'enum' => 'The selected :attribute is invalid.',
     'exists' => 'The selected :attribute is invalid.',

src/Illuminate/Validation/Concerns/ReplacesAttributes.php

@@ -129,6 +129,20 @@ protected function replaceDigitsBetween($message, $attribute, $rule, $parameters
         return $this->replaceBetween($message, $attribute, $rule, $parameters);
     }
 
+    /**
+     * Replace all place-holders for the encoding rule.
+     *
+     * @param  string  $message
+     * @param  string  $attribute
+     * @param  string  $rule
+     * @param  array<int,string>  $parameters
+     * @return string
+     */
+    protected function replaceEncoding($message, $attribute, $rule, $parameters)
+    {
+        return str_replace(':encoding', $parameters[0], $message);
+    }
+
     /**
      * Replace all place-holders for the extensions rule.
      *

src/Illuminate/Validation/Concerns/ValidatesAttributes.php

@@ -959,6 +959,25 @@ public function validateEmail($attribute, $value, $parameters)
         return $emailValidator->isValid($value, new MultipleValidationWithAnd($validations));
     }
 
+    /**
+     * Validate the encoding of an attribute.
+     *
+     * @param  string  $attribute
+     * @param  mixed  $value
+     * @param  array<int, int|string>  $parameters
+     * @return bool
+     */
+    public function validateEncoding($attribute, $value, $parameters)
+    {
+        $this->requireParameterCount(1, $parameters, 'encoding');
+
+        if (! in_array(mb_strtolower($parameters[0]), array_map(mb_strtolower(...), mb_list_encodings()))) {
+            throw new InvalidArgumentException("Validation rule encoding parameter [{$parameters[0]}] is not a valid encoding.");
+        }
+
+        return mb_check_encoding($value instanceof File ? $value->getContent() : $value, $parameters[0]);
+    }
+
     /**
      * Validate the existence of an attribute value in a database table.
      *

src/Illuminate/Validation/Rules/File.php

@@ -45,6 +45,13 @@ class File implements Rule, DataAwareRule, ValidatorAwareRule
      */
     protected $maximumFileSize = null;
 
+    /**
+     * The required file encoding.
+     *
+     * @var string|null
+     */
+    protected $encoding = null;
+
     /**
      * An array of custom rules that will be merged into the validation rules.
      *
@@ -205,6 +212,19 @@ public function max($size)
         return $this;
     }
 
+    /**
+     * Indicate that the uploaded file should be in the given encoding.
+     *
+     * @param  string  $encoding
+     * @return $this
+     */
+    public function encoding($encoding)
+    {
+        $this->encoding = $encoding;
+
+        return $this;
+    }
+
     /**
      * Convert a potentially human-friendly file size to kilobytes.
      *
@@ -291,6 +311,10 @@ protected function buildValidationRules()
             default => "size:{$this->minimumFileSize}",
         };
 
+        if ($this->encoding) {
+            $rules[] = 'encoding:'.$this->encoding;
+        }
+
         return array_merge(array_filter($rules), $this->customRules);
     }
 

src/Illuminate/Validation/Validator.php

@@ -188,6 +188,7 @@ class Validator implements ValidatorContract
     protected $fileRules = [
         'Between',
         'Dimensions',
+        'Encoding',
         'Extensions',
         'File',
         'Image',

tests/Validation/ValidationFileRuleTest.php

@@ -357,6 +357,49 @@ public function testMaxWithHumanReadableSizeAndMultipleValue()
         );
     }
 
+    public function testEncoding()
+    {
+        // ASCII file containing UTF-8.
+        $this->fails(
+            File::default()->encoding('ascii'),
+            UploadedFile::fake()->createWithContent('foo.txt', '✌️'),
+            ['validation.encoding'],
+        );
+
+        // UTF-8 file containing invalid UTF-8 byte sequence.
+        $this->fails(
+            File::default()->encoding('utf-8'),
+            UploadedFile::fake()->createWithContent('foo.txt', "\xf0\x28\x8c\x28"),
+            ['validation.encoding'],
+        );
+
+        $this->passes(
+            File::default()->encoding('utf-8'),
+            UploadedFile::fake()->createWithContent('foo.txt', '✌️'),
+        );
+
+        $this->passes(
+            File::default()->encoding('utf-8'),
+            [
+                UploadedFile::fake()->createWithContent('foo-1.txt', '✌️'),
+                UploadedFile::fake()->createWithContent('foo-2.txt', '👍'),
+            ]
+        );
+    }
+
+    public function testEncodingWithInvalidParameter()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Validation rule encoding parameter "FOOBAR" is not a valid encoding.');
+
+        // Invalid encoding.
+        $this->fails(
+            File::default()->encoding('FOOBAR'),
+            UploadedFile::fake()->createWithContent('foo.txt', ''),
+            ['validation.encoding'],
+        );
+    }
+
     public function testMacro()
     {
         File::macro('toDocument', function () {