Implement automatic record updating via HTTP(S) (sometimes called dynamic DNS)

1 files changed, 95 insertions, 7 deletions

diff --git a/dns.php b/dns.php
index cbef901..8a3454d 100644
--- a/dns.php
+++ b/dns.php
@@ -59,7 +59,7 @@ function sshrun($command) {
   return stream_get_contents($stream_out);
 }
 
-function getzone($domain, $password) {
+function getzone($domain, $password = null) {
   if (!preg_match('/^[0-9A-Za-z\.\-]*$/', $domain)) {
     die("invalid domain");
   }
@@ -69,19 +69,24 @@ function getzone($domain, $password) {
   $zonelines = explode("\n", $string);
   $zonehash = explode(" ", $zonelines[0]);
 
-  if (strtolower($zonehash[sizeof($zonehash) - 1]) == strtolower($password)) {
+  // Not all calls to this function need a password
+  if (!$password) {
+    return $string;
+  } else if (strtolower($zonehash[sizeof($zonehash) - 1]) == strtolower($password)) {
     return $string;
   } else {
     return;
   }
 }
 
-function writezone($domain, $password, $zonetext) {
+function writezone($domain, $zonetext, $password = null) {
   if (!preg_match('/^[0-9A-Za-z\.\-]*$/', $domain)) {
     die("invalid domain");
   }
 
-  if (!getzone($domain, $password)) {
+  // Not all calls to this function need a password. If passwords are in use,
+  // check to make sure it is correct.
+  if ($password && !getzone($domain, $password)) {
     die("somehow the password went bad");
   }
 
@@ -93,7 +98,81 @@ function writezone($domain, $password, $zonetext) {
 
 // Main entry point
 
-if (isset($_POST['domain']) && isset($_POST['password']) && !isset($_POST['zonetext'])) {
+if (isset($_GET['mode']) && isset($_GET['zone']) && isset($_GET['hash'])) {
+  // Some sort of mode (at the moment only "update" is supported
+  if ($_GET['mode'] == "update") {
+    // An auto update is being requested. This is where one or more zone records
+    // are requested to be updated to the requester's IP address.
+    $zonetext = getzone($_GET['zone']);
+    // Only use \n for newlines
+    $zonetext = str_replace("\r", "", $zonetext);
+    // Split into individual lines
+    $zonelines = explode("\n", $zonetext);
+    $matches = array();
+    // Find lines that ended with the hash provided (if any)
+    $i = 0;
+    foreach ($zonelines as $line) {
+      if (preg_match("/" . $_GET['hash'] . "$/", $line)) {
+        array_push($matches, array($i, $line));
+      }
+      $i++;
+    }
+    // Go through the lines that matched the hash and see if we can find an update to do
+    foreach ($matches as $arrline) {
+      $line = $arrline[1];
+      // Get rid of the comment
+      $exploded = explode(";", $line);
+      $record = $exploded[0];
+      // Split into individual components
+      $parts = preg_split("/\s+/", $record);
+      // Make sure the last element isn't blank (would happen if the comment had a space before it)
+      while ($parts[sizeof($parts) - 1] == "") {
+        array_pop($parts);
+      }
+      // See if the record type on this line matches the request address type (e.g. an A record update must be requested by an IPv4 address)
+      if ($parts[sizeof($parts) - 2] == "A") {
+        // Regex for IPv4 address
+        if (preg_match("/\b((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(\.|$)){4}\b/", $_SERVER['REMOTE_ADDR'])) {
+          $parts[sizeof($parts) - 1] = $_SERVER['REMOTE_ADDR'];
+        } else {
+          die("A record and non-IPv4 request - bad.");
+        }
+      } else if ($parts[sizeof($parts) - 2] == "AAAA") {
+        // Regex for IPv6 address
+        if (preg_match("/(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))/", $_SERVER['REMOTE_ADDR'])) {
+          $parts[sizeof($parts) - 1] = $_SERVER['REMOTE_ADDR'];
+        } else {
+          die("AAAA record and non-IPv6 request - bad.");
+        }
+      } else {
+        die("Unrecognised record type!");
+      }
+      // Update original zone file array with the new line at the correct position
+      $zonelines[$arrline[0]] = preg_replace("/[A-Za-z0-9:\.]+([[:space:]]*;)/", $parts[sizeof($parts) - 1] . "$1", $line);
+    }
+    // Next we need to turn the zone file array back into a string again
+    $newzonetext = "";
+    // If the last element was blank, remove it since we'll add a new blank ourselves
+    if ($zonelines[sizeof($zonelines) - 1] == "") {
+      array_pop($zonelines);
+    }
+    // Do the actual converstion to string
+    foreach ($zonelines as $line) {
+      $newzonetext .= $line . "\n";
+    }
+    // See if there was actually a change as a result of this request...
+    if ($zonetext == $newzonetext) {
+      // ...if not, abandon ship
+      echo "<p>no changes detected :)</p>";
+    } else {
+      // ...if so, increment the serial number and...
+      $newzonetext = incrementserial($newzonetext)[0];
+      // ...finally write the zone with the updated record(s)
+      writezone($_GET['zone'], $newzonetext);
+      echo "<p>record&#40;s&#41; updated :)</p>";
+    }
+  }
+} else if (isset($_POST['domain']) && isset($_POST['password']) && !isset($_POST['zonetext'])) {
   if (!preg_match('/^[0-9A-Za-z\.\-]*$/', $_POST['domain'])) {
     die("invalid domain");
   }
@@ -102,7 +181,16 @@ if (isset($_POST['domain']) && isset($_POST['password']) && !isset($_POST['zonet
 
   if ($zonefile = getzone($_POST['domain'], $password)) {
 ?>
-    <p>Your zonefile is below. Ensure the first line always ends with a SHA-256 hash of your chosen password.</p>
+    <p>1. Your zonefile is below.</p>
+    <p>2. Ensure the first line always ends with a SHA-256 hash of your chosen password.</p>
+    <p>3. To automatically update a particular record, give the line a comment ending with a secret ID &#40;e.g. a SHA-256 hash&#41;, e.g.:</p>
+    <pre>
+test    300     IN      A       192.168.0.1 ; sha256 = 7f480e744a79953eb916b68f540e0eeec6f9cf23edf4aa08cc1cdf5f077c0f6f
+test    300     IN      AAAA    ::1 ; sha256 = b493d48364afe44d11c0165cf470a4164d1e2609911ef998be868d46ade3de4e
+    </pre>
+    <p>And then do an HTTP&#40;S&#41; request to:</p>
+    <pre>https://bladns.net/dns.php?mode=update&zone=<strong>yourdomain.tld</strong>&hash=<strong>yourid</strong></pre>
+    <p>Your record will be updated with the IP you did the request from.</p>
     <form action="dns.php" method="post">
     <textarea rows="24" cols="80" name="zonetext" autofocus><?php echo $zonefile; ?></textarea><br>
 <?php
@@ -127,7 +215,7 @@ if (isset($_POST['domain']) && isset($_POST['password']) && !isset($_POST['zonet
   if (isset($_POST['increment'])) {
     $zonetext = incrementserial($zonetext)[0];
   }
-  writezone($_POST['domain'], $_POST['password'], $zonetext);
+  writezone($_POST['domain'], $zonetext, $_POST['password']);
   echo "<p>all done :)</p>";
 } else {
 ?>