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diff --git a/src/applications/differential/storage/DifferentialChangeset.php b/src/applications/differential/storage/DifferentialChangeset.php
--- a/src/applications/differential/storage/DifferentialChangeset.php
+++ b/src/applications/differential/storage/DifferentialChangeset.php
@@ -173,7 +173,7 @@
}
public function getAnchorName() {
- return 'change-'.PhabricatorHash::digestForIndex($this->getFilename());
+ return 'change-'.PhabricatorHash::digestForAnchor($this->getFilename());
}
public function getAbsoluteRepositoryPath(
diff --git a/src/infrastructure/util/PhabricatorHash.php b/src/infrastructure/util/PhabricatorHash.php
--- a/src/infrastructure/util/PhabricatorHash.php
+++ b/src/infrastructure/util/PhabricatorHash.php
@@ -3,6 +3,7 @@
final class PhabricatorHash extends Phobject {
const INDEX_DIGEST_LENGTH = 12;
+ const ANCHOR_DIGEST_LENGTH = 12;
/**
* Digest a string using HMAC+SHA1.
@@ -38,8 +39,8 @@
* related hashing (for general purpose hashing, see @{method:digest}).
*
* @param string Input string.
- * @return string 12-byte, case-sensitive alphanumeric hash of the string
- * which
+ * @return string 12-byte, case-sensitive, mostly-alphanumeric hash of
+ * the string.
*/
public static function digestForIndex($string) {
$hash = sha1($string, $raw_output = true);
@@ -63,6 +64,62 @@
return $result;
}
+ /**
+ * Digest a string for use in HTML page anchors. This is similar to
+ * @{method:digestForIndex} but produces purely alphanumeric output.
+ *
+ * This tries to be mostly compatible with the index digest to limit how
+ * much stuff we're breaking by switching to it. For additional discussion,
+ * see T13045.
+ *
+ * @param string Input string.
+ * @return string 12-byte, case-sensitive, purely-alphanumeric hash of
+ * the string.
+ */
+ public static function digestForAnchor($string) {
+ $hash = sha1($string, $raw_output = true);
+
+ static $map;
+ if ($map === null) {
+ $map = '0123456789'.
+ 'abcdefghij'.
+ 'klmnopqrst'.
+ 'uvwxyzABCD'.
+ 'EFGHIJKLMN'.
+ 'OPQRSTUVWX'.
+ 'YZ';
+ }
+
+ $result = '';
+ $accum = 0;
+ $map_size = strlen($map);
+ for ($ii = 0; $ii < self::ANCHOR_DIGEST_LENGTH; $ii++) {
+ $byte = ord($hash[$ii]);
+ $low_bits = ($byte & 0x3F);
+ $accum = ($accum + $byte) % $map_size;
+
+ if ($low_bits < $map_size) {
+ // If an index digest would produce any alphanumeric character, just
+ // use that character. This means that these digests are the same as
+ // digests created with "digestForIndex()" in all positions where the
+ // output character is some character other than "." or "_".
+ $result .= $map[$low_bits];
+ } else {
+ // If an index digest would produce a non-alphumeric character ("." or
+ // "_"), pick an alphanumeric character instead. We accumulate an
+ // index into the alphanumeric character list to try to preserve
+ // entropy here. We could use this strategy for all bytes instead,
+ // but then these digests would differ from digests created with
+ // "digestForIndex()" in all positions, instead of just a small number
+ // of positions.
+ $result .= $map[$accum];
+ }
+ }
+
+ return $result;
+ }
+
+
public static function digestToRange($string, $min, $max) {
if ($min > $max) {
throw new Exception(pht('Maximum must be larger than minimum.'));
diff --git a/src/infrastructure/util/__tests__/PhabricatorHashTestCase.php b/src/infrastructure/util/__tests__/PhabricatorHashTestCase.php
--- a/src/infrastructure/util/__tests__/PhabricatorHashTestCase.php
+++ b/src/infrastructure/util/__tests__/PhabricatorHashTestCase.php
@@ -52,4 +52,47 @@
pht('Distinct characters in hash of: %s', $input));
}
+ public function testHashForAnchor() {
+ $map = array(
+ // For inputs with no "." or "_" in the output, digesting for an index
+ // or an anchor should be the same.
+ 'dog' => array(
+ 'Aliif7Qjd5ct',
+ 'Aliif7Qjd5ct',
+ ),
+ // When an output would contain "." or "_", it should be replaced with
+ // an alphanumeric character in those positions instead.
+ 'fig' => array(
+ 'OpB9tY4i.MOX',
+ 'OpB9tY4imMOX',
+ ),
+ 'cot' => array(
+ '_iF26XU_PsVY',
+ '3iF26XUkPsVY',
+ ),
+ // The replacement characters are well-distributed and generally keep
+ // the entropy of the output high: here, "_" characters in the initial
+ // positions of the digests of "cot" (above) and "dug" (this test) have
+ // different outputs.
+ 'dug' => array(
+ '_XuQnp0LUlUW',
+ '7XuQnp0LUlUW',
+ ),
+ );
+
+ foreach ($map as $input => $expect) {
+ list($expect_index, $expect_anchor) = $expect;
+
+ $this->assertEqual(
+ $expect_index,
+ PhabricatorHash::digestForIndex($input),
+ pht('Index digest of "%s".', $input));
+
+ $this->assertEqual(
+ $expect_anchor,
+ PhabricatorHash::digestForAnchor($input),
+ pht('Anchor digest of "%s".', $input));
+ }
+ }
+
}

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