added host validation for urls

includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php

@@ -699,6 +699,19 @@ private function validate_attr_spec_list_for_node( $node, $attr_spec_list ) {
 				}
 			}
 
+			/*
+			 * If given attribute's value is a URL with a host, the host must
+			 * be valid
+			 */
+			if ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ] ) ) {
+				$result = $this->check_attr_spec_rule_valid_url( $node, $attr_name, $attr_spec_rule );
+				if ( AMP_Rule_Spec::PASS === $result ) {
+					$score++;
+				} elseif ( AMP_Rule_Spec::FAIL === $result ) {
+					return 0;
+				}
+			}
+
 			/*
 			 * If the given attribute's value is *not* a relative path, and the rule's
 			 * value is `false`, then pass.
@@ -877,6 +890,9 @@ private function delegated_sanitize_disallowed_attribute_values_in_node( $node,
 			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOWED_PROTOCOL ] ) &&
 				AMP_Rule_Spec::FAIL === $this->check_attr_spec_rule_allowed_protocol( $node, $attr_name, $attr_spec_rule ) ) {
 				$should_remove_node = true;
+			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ] ) &&
+				AMP_Rule_Spec::FAIL === $this->check_attr_spec_rule_valid_url( $node, $attr_name, $attr_spec_rule ) ) {
+				$should_remove_node = true;
 			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_RELATIVE ] ) &&
 				AMP_Rule_Spec::FAIL === $this->check_attr_spec_rule_disallowed_relative( $node, $attr_name, $attr_spec_rule ) ) {
 				$should_remove_node = true;
@@ -1122,6 +1138,49 @@ private function check_attr_spec_rule_value_regex_casei( $node, $attr_name, $att
 		return AMP_Rule_Spec::NOT_APPLICABLE;
 	}
 
+	/**
+	 * Check if attribute has a valid host value
+	 *
+	 * @since 0.7
+	 *
+	 * @param DOMElement       $node           Node.
+	 * @param string           $attr_name      Attribute name.
+	 * @param array[]|string[] $attr_spec_rule Attribute spec rule.
+	 *
+	 * @return string:
+	 *      - AMP_Rule_Spec::PASS - $attr_name has a value that matches the rule.
+	 *      - AMP_Rule_Spec::FAIL - $attr_name has a value that does *not* match rule.
+	 *      - AMP_Rule_Spec::NOT_APPLICABLE - $attr_name does not exist or there
+	 *                                        is no rule for this attribute.
+	 */
+	private function check_attr_spec_rule_valid_url( $node, $attr_name, $attr_spec_rule ) {
+		if ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ] ) ) {
+			if ( $node->hasAttribute( $attr_name ) ) {
+				$attr_value   = $node->getAttribute( $attr_name );
+				$attr_value   = preg_replace( '/\s*,\s*/', ',', $attr_value );
+				$urls_to_test = explode( ',', $attr_value );
+
+				foreach ( $urls_to_test as $url ) {
+					// Check if the host contains invalid chars.
+					$url_host = wp_parse_url( urldecode( $url ), PHP_URL_HOST );
+					if ( $url_host && preg_match( '/[!"#$%&\'()*+,\/:;<=>?@[\]^`{|}~\s]/i', $url_host ) ) {
+						return AMP_Rule_Spec::FAIL;
+					}
+
+					// Check if the protocol contains invalid chars.
+					$url_scheme = AMP_WP_Utils::parse_url( $url, PHP_URL_SCHEME );
+					if ( $url_scheme && preg_match( '/[!"#$%&\'()*+,\/:;<=>?@[\]^`{|}~\s]/i', $url_scheme ) ) {
+						return AMP_Rule_Spec::FAIL;
+					}
+				}
+
+				return AMP_Rule_Spec::PASS;
+			}
+		}
+
+		return AMP_Rule_Spec::NOT_APPLICABLE;
+	}
+
 	/**
 	 * Check if attribute has a protocol value rule determine if it matches.
 	 *

tests/test-tag-and-attribute-sanitizer.php

@@ -680,6 +680,15 @@ public function get_body_data() {
 				'<a class="foo" href="">value</a>',
 			),
 
+			'a_with_wrong_host'                                         => array(
+				'<a class="foo" href="http://foo bar">value</a>',
+				'<a class="foo" href="">value</a>',
+			),
+			'a_with_mail_host'                                         => array(
+				'<a class="foo" href="mail to:[email protected]">value</a>',
+				'<a class="foo" href="">value</a>',
+			),
+
 			// font is removed so we should check that other elements are checked as well.
 			'font_with_other_bad_elements'                              => array(
 				'<font size="1">Headline</font><span style="color: blue">Span</span>',