Program: CWE-94
Project: CVE-2013-3239
Buggy source:
<?php
/* vim: set expandtab sw=4 ts=4 sts=4: */
/**
 * This is in a separate script because it's called from a number of scripts
 *
 * @package PhpMyAdmin
 */

/**
 * Checks whether given link is valid
 *
 * @param string $url URL to check
 * @return boolean True if string can be used as link
 */
function PMA_checkLink($url)
{
    $valid_starts = array(
        'http://',
        'https://',
        './url.php?url=http%3A%2F%2F',
        './url.php?url=https%3A%2F%2F',
    );
    if (defined('PMA_SETUP')) {
        $valid_starts[] = '../Documentation.html';
        $valid_starts[] = '?page=form&';
    } else {
        $valid_starts[] = './Documentation.html';
    }
    foreach ($valid_starts as $val) {
        if (substr($url, 0, strlen($val)) == $val) {
            return true;
        }
    }
    return false;
}

/**
 * Callback function for replacing [a@link@target] links in bb code.
 *
 * @param array $found Array of preg matches
 * @return string Replaced string
 */
function PMA_replaceBBLink($found)
{
    /* Check for valid link */
    if (! PMA_checkLink($found[1])) {
        return $found[0];
    }
    /* a-z and _ allowed in target */
    if (! empty($found[3]) && preg_match('/[^a-z_]+/i', $found[3])) {
        return $found[0];
    }

    /* Construct target */
    $target = '';
    if (! empty($found[3])) {
        $target = ' target="' . $found[3] . '"';
    }

    /* Construct url */
    if (substr($found[1], 0, 4) == 'http') {
        $url = PMA_linkURL($found[1]);
    } else {
        $url = $found[1];
    }

    return '<a href="' . $url . '"' . $target . '>';
}

/**
 * Sanitizes $message, taking into account our special codes
 * for formatting.
 *
 * If you want to include result in element attribute, you should escape it.
 *
 * Examples:
 *
 * <p><?php echo PMA_sanitize($foo); ?></p>
 *
 * <a title="<?php echo PMA_sanitize($foo, true); ?>">bar</a>
 *
 * @param string  $message the message
 * @param boolean $escape  whether to escape html in result
 * @param boolean $safe    whether string is safe (can keep < and > chars)
 * @return  string   the sanitized message
 */
function PMA_sanitize($message, $escape = false, $safe = false)
{
    if (!$safe) {
        $message = strtr($message, array('<' => '&lt;', '>' => '&gt;'));
    }
    /* Interpret bb code */
    $replace_pairs = array(
        '[i]'       => '<em>',      // deprecated by em
        '[/i]'      => '</em>',     // deprecated by em
        '[em]'      => '<em>',
        '[/em]'     => '</em>',
        '[b]'       => '<strong>',  // deprecated by strong
        '[/b]'      => '</strong>', // deprecated by strong
        '[strong]'  => '<strong>',
        '[/strong]' => '</strong>',
        '[tt]'      => '<code>',    // deprecated by CODE or KBD
        '[/tt]'     => '</code>',   // deprecated by CODE or KBD
        '[code]'    => '<code>',
        '[/code]'   => '</code>',
        '[kbd]'     => '<kbd>',
        '[/kbd]'    => '</kbd>',
        '[br]'      => '<br />',
        '[/a]'      => '</a>',
        '[sup]'      => '<sup>',
        '[/sup]'      => '</sup>',
    );
    /* Adjust links for setup, which lives in subfolder */
    if (defined('PMA_SETUP')) {
        $replace_pairs['[a@Documentation.html'] = '[a@../Documentation.html';
    } else {
        $replace_pairs['[a@Documentation.html'] = '[a@./Documentation.html';
    }
    $message = strtr($message, $replace_pairs);

    /* Match links in bb code ([a@url@target], where @target is options) */
    $pattern = '/\[a@([^]"@]*)(@([^]"]*))?\]/';

    /* Find and replace all links */
    $message = preg_replace_callback($pattern, 'PMA_replaceBBLink', $message);

    /* Possibly escape result */
    if ($escape) {
        $message = htmlspecialchars($message);
    }

    return $message;
}


/**
 * Sanitize a filename by removing anything besides A-Za-z0-9_.-
 *
 * Intended usecase:
 *    When using a filename in a Content-Disposition header the value should not contain ; or "
 *
 * @param   string  The filename
 *
 * @return  string  the sanitized filename
 *
 */
function PMA_sanitize_filename($filename) {
    $filename = preg_replace('/[^A-Za-z0-9_.-]/', '_', $filename);
    return $filename;
}

?>


Fixed version (ground truth):
<?php
/* vim: set expandtab sw=4 ts=4 sts=4: */
/**
 * This is in a separate script because it's called from a number of scripts
 *
 * @package PhpMyAdmin
 */

/**
 * Checks whether given link is valid
 *
 * @param string $url URL to check
 * @return boolean True if string can be used as link
 */
function PMA_checkLink($url)
{
    $valid_starts = array(
        'http://',
        'https://',
        './url.php?url=http%3A%2F%2F',
        './url.php?url=https%3A%2F%2F',
    );
    if (defined('PMA_SETUP')) {
        $valid_starts[] = '../Documentation.html';
        $valid_starts[] = '?page=form&';
    } else {
        $valid_starts[] = './Documentation.html';
    }
    foreach ($valid_starts as $val) {
        if (substr($url, 0, strlen($val)) == $val) {
            return true;
        }
    }
    return false;
}

/**
 * Callback function for replacing [a@link@target] links in bb code.
 *
 * @param array $found Array of preg matches
 * @return string Replaced string
 */
function PMA_replaceBBLink($found)
{
    /* Check for valid link */
    if (! PMA_checkLink($found[1])) {
        return $found[0];
    }
    /* a-z and _ allowed in target */
    if (! empty($found[3]) && preg_match('/[^a-z_]+/i', $found[3])) {
        return $found[0];
    }

    /* Construct target */
    $target = '';
    if (! empty($found[3])) {
        $target = ' target="' . $found[3] . '"';
    }

    /* Construct url */
    if (substr($found[1], 0, 4) == 'http') {
        $url = PMA_linkURL($found[1]);
    } else {
        $url = $found[1];
    }

    return '<a href="' . $url . '"' . $target . '>';
}

/**
 * Sanitizes $message, taking into account our special codes
 * for formatting.
 *
 * If you want to include result in element attribute, you should escape it.
 *
 * Examples:
 *
 * <p><?php echo PMA_sanitize($foo); ?></p>
 *
 * <a title="<?php echo PMA_sanitize($foo, true); ?>">bar</a>
 *
 * @param string  $message the message
 * @param boolean $escape  whether to escape html in result
 * @param boolean $safe    whether string is safe (can keep < and > chars)
 * @return  string   the sanitized message
 */
function PMA_sanitize($message, $escape = false, $safe = false)
{
    if (!$safe) {
        $message = strtr($message, array('<' => '&lt;', '>' => '&gt;'));
    }
    /* Interpret bb code */
    $replace_pairs = array(
        '[i]'       => '<em>',      // deprecated by em
        '[/i]'      => '</em>',     // deprecated by em
        '[em]'      => '<em>',
        '[/em]'     => '</em>',
        '[b]'       => '<strong>',  // deprecated by strong
        '[/b]'      => '</strong>', // deprecated by strong
        '[strong]'  => '<strong>',
        '[/strong]' => '</strong>',
        '[tt]'      => '<code>',    // deprecated by CODE or KBD
        '[/tt]'     => '</code>',   // deprecated by CODE or KBD
        '[code]'    => '<code>',
        '[/code]'   => '</code>',
        '[kbd]'     => '<kbd>',
        '[/kbd]'    => '</kbd>',
        '[br]'      => '<br />',
        '[/a]'      => '</a>',
        '[sup]'      => '<sup>',
        '[/sup]'      => '</sup>',
    );
    /* Adjust links for setup, which lives in subfolder */
    if (defined('PMA_SETUP')) {
        $replace_pairs['[a@Documentation.html'] = '[a@../Documentation.html';
    } else {
        $replace_pairs['[a@Documentation.html'] = '[a@./Documentation.html';
    }
    $message = strtr($message, $replace_pairs);

    /* Match links in bb code ([a@url@target], where @target is options) */
    $pattern = '/\[a@([^]"@]*)(@([^]"]*))?\]/';

    /* Find and replace all links */
    $message = preg_replace_callback($pattern, 'PMA_replaceBBLink', $message);

    /* Possibly escape result */
    if ($escape) {
        $message = htmlspecialchars($message);
    }

    return $message;
}


/**
 * Sanitize a filename by removing anything besides legit characters 
 *
 * Intended usecase:
 *    When using a filename in a Content-Disposition header the value
 *    should not contain ; or "
 *
 *    When exporting, avoiding generation of an unexpected double-extension file
 *
 * @param   string  The filename
 * @param   boolean Whether to also replace dots 
 *
 * @return  string  the sanitized filename
 *
 */
function PMA_sanitize_filename($filename, $replaceDots = false) {
    $pattern = '/[^A-Za-z0-9_';
    // if we don't have to replace dots
    if (! $replaceDots) {
        // then add the dot to the list of legit characters
        $pattern .= '.';
    }
    $pattern .= '-]/';
    $filename = preg_replace($pattern, '_', $filename);
    return $filename;
}

?>