Sophie: php-manual-en-4.3.0-2mdk noarch

php-manual-en-4.3.0-2mdk.noarch.rpm

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><DIV
CLASS="chapter"
><H1
><A
NAME="features.safe-mode"
>Chapter 22. Safe Mode</A
></H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="features.safe-mode.html#ini.sect.safe-mode"
>Security and Safe Mode</A
></DT
><DT
><A
HREF="features.safe-mode.functions.html"
>Functions restricted/disabled by safe mode</A
></DT
></DL
></DIV
><P
>&#13;   The PHP safe mode is an attempt to solve the shared-server security
   problem. It is architecturally incorrect to try to solve this
   problem at the PHP level, but since the alternatives at the web
   server and OS levels aren't very realistic, many people,
   especially ISP's, use safe mode for now. 
  </P
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="ini.sect.safe-mode"
></A
>Security and Safe Mode</H1
><P
>&#13;    <DIV
CLASS="table"
><A
NAME="AEN6100"
></A
><P
><B
>Table 22-1. Security and Safe Mode Configuration Directives</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Name</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Default</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Changeable</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>safe_mode</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>safe_mode_gid</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>safe_mode_include_dir</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>NULL</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>safe_mode_exec_dir</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>""</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>safe_mode_allowed_env_vars</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>safe_mode_protected_env_vars</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>LD_LIBRARY_PATH</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>open_basedir</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>NULL</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>disable_functions</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>""</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM</TD
></TR
></TBODY
></TABLE
></DIV
>
    For further details and definition of the PHP_INI_* constants see
    <A
HREF="function.ini-set.html"
><B
CLASS="function"
>ini_set()</B
></A
>.
   </P
><P
>&#13;    Here is a short explanation of the configuration directives.
    <P
></P
><DIV
CLASS="variablelist"
><DL
><DT
><A
NAME="ini.safe-mode"
></A
><TT
CLASS="parameter"
><I
>safe_mode</I
></TT
>
       <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
>&#13;        Whether to enable PHP's safe mode. Read the
        <A
HREF="security.html"
>Security</A
> and chapter for more
        information.
       </P
></DD
><DT
><A
NAME="ini.safe-mode-gid"
></A
><TT
CLASS="parameter"
><I
>safe_mode_gid</I
></TT
>
       <A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
>&#13;        By default, Safe Mode does a UID compare check when
        opening files. If you want to relax this to a GID compare,
        then turn on safe_mode_gid.
        Whether to use <TT
CLASS="literal"
>UID</TT
> (<TT
CLASS="constant"
><B
>FALSE</B
></TT
>) or
        <TT
CLASS="literal"
>GID</TT
> (<TT
CLASS="constant"
><B
>TRUE</B
></TT
>) checking upon file
        access.
       </P
></DD
><DT
><A
NAME="ini.safe-mode-include-dir"
></A
><TT
CLASS="parameter"
><I
>safe_mode_include_dir</I
></TT
>
       <A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
>&#13;        <TT
CLASS="literal"
>UID</TT
>/<TT
CLASS="literal"
>GID</TT
> checks are bypassed when
        including files from this directory and its subdirectories (directory
        must also be in <A
HREF="configuration.directives.html#ini.include-path"
>include_path</A
>
        or full path must including).
       </P
><P
>&#13;        As of PHP 4.2.0, this directive can take a semi-colon separated 
        path in a similar fashion to the
        <A
HREF="configuration.directives.html#ini.include-path"
>include_path</A
> directive,
        rather than just a single directory.
       </P
><P
>&#13;        The restriction specified is actually a prefix, not a directory name. 
        This means that "safe_mode_include_dir = /dir/incl" also allows
        access to "/dir/include" and "/dir/incls" if they exist.  When you 
        want to restrict access to only the specified directory, end with a 
        slash. For example: "safe_mode_include_dir = /dir/incl/"
       </P
></DD
><DT
><A
NAME="ini.safe-mode-exec-dir"
></A
><TT
CLASS="parameter"
><I
>safe_mode_exec_dir</I
></TT
>
       <A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
>&#13;        If PHP is used in safe mode, <A
HREF="function.system.html"
><B
CLASS="function"
>system()</B
></A
> and the other
        <A
HREF="ref.exec.html"
>functions executing system programs</A
>
        refuse to start programs that are not in this directory.
       </P
></DD
><DT
><A
NAME="ini.safe-mode-allowed-env-vars"
></A
><TT
CLASS="parameter"
><I
>safe_mode_allowed_env_vars</I
></TT
>
       <A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
>&#13;        Setting certain environment variables may be a potential security breach.
        This directive contains a comma-delimited list of prefixes. In Safe Mode,
        the user may only alter environment variables whose names begin with the
        prefixes supplied here. By default, users will only be able to set
        environment variables that begin with PHP_ (e.g. PHP_FOO=BAR).
       </P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
         If this directive is empty, PHP will let the user modify ANY
         environment variable!
        </P
></BLOCKQUOTE
></DIV
></DD
><DT
><A
NAME="ini.safe-mode-protected-env-vars"
></A
><TT
CLASS="parameter"
><I
>safe_mode_protected_env_vars</I
></TT
>
       <A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
>&#13;        This directive contains a comma-delimited list of environment
        variables that the end user won't be able to change using
        <A
HREF="function.putenv.html"
><B
CLASS="function"
>putenv()</B
></A
>. These variables will be protected
        even if safe_mode_allowed_env_vars is set to allow to change them.
       </P
></DD
><DT
><A
NAME="ini.open-basedir"
></A
><TT
CLASS="parameter"
><I
>open_basedir</I
></TT
>
       <A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
>&#13;        Limit the files that can be opened by PHP to the specified
        directory-tree, including the file itself.  This directive 
        is <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>NOT</I
></SPAN
> affected by whether Safe Mode is 
        turned On or Off.
       </P
><P
>&#13;        When a script tries to open a file with,
        for example, fopen or gzopen, the location of the file is
        checked. When the file is outside the specified directory-tree,
        PHP will refuse to open it. All symbolic links are resolved,
        so it's not possible to avoid this restriction with a symlink.
       </P
><P
>&#13;        The special value <SPAN
CLASS="systemitem"
>.</SPAN
>
        indicates that the directory in which the script is stored will
        be used as base-directory.
       </P
><P
>&#13;        Under Windows, separate the directories with a semicolon. On all
        other systems, separate the directories with a colon. As an Apache
        module, open_basedir paths from parent directories are now
        automatically inherited.
       </P
><P
>&#13;         The restriction specified with open_basedir is actually a
         prefix, not a directory name.  This means that "open_basedir =
         /dir/incl" also allows access to "/dir/include" and
         "/dir/incls" if they exist. When you want to restrict access
         to only the specified directory, end with a slash. For example:
         "open_basedir = /dir/incl/"
       </P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
         Support for multiple directories was added in 3.0.7.
        </P
></BLOCKQUOTE
></DIV
><P
>&#13;        The default is to allow all files to be opened.
       </P
></DD
><DT
><A
NAME="ini.disable-functions"
></A
><TT
CLASS="parameter"
><I
>disable_functions</I
></TT
>
       <A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
>&#13;        This directive allows you to disable certain functions for 
        <A
HREF="security.html"
>security</A
> reasons. It takes 
        on a comma-dilimited list of function names. disable_functions
        is not affected by <A
HREF="features.safe-mode.html#ini.safe-mode"
>Safe Mode</A
>.
       </P
><P
>&#13;        This directive must be set in <TT
CLASS="filename"
>php.ini</TT
> For example, you 
        cannot set this in <TT
CLASS="filename"
>httpd.conf</TT
>.
       </P
></DD
></DL
></DIV
>
   </P
><P
>&#13;    See also: <A
HREF="configuration.directives.html#ini.register-globals"
>register_globals</A
>,
    <A
HREF="ref.errorfunc.html#ini.display-errors"
>display_errors</A
>, and
    <A
HREF="ref.errorfunc.html#ini.log-errors"
>log_errors</A
>
   </P
><P
>&#13;   When <A
HREF="features.safe-mode.html#ini.safe-mode"
>safe_mode</A
> is on, PHP checks to see 
   if the owner of the current script matches the owner of the file to be 
   operated on by a file function. For example: 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="ls"
>-rw-rw-r--    1 rasmus   rasmus       33 Jul  1 19:20 script.php 
-rw-r--r--    1 root     root       1116 May 26 18:01 /etc/passwd</PRE
></TD
></TR
></TABLE
>
   Running this script.php 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
>&#60;?php
 readfile('/etc/passwd'); 
?&#62;</PRE
></TD
></TR
></TABLE
>
   results in this error when safe mode is enabled: 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Warning: SAFE MODE Restriction in effect. The script whose uid is 500 is not 
allowed to access /etc/passwd owned by uid 0 in /docroot/script.php on line 2</PRE
></TD
></TR
></TABLE
>
  </P
><P
>&#13;   However, there may be environments where a strict <TT
CLASS="literal"
>UID</TT
>
   check is not appropriate and a relaxed <TT
CLASS="literal"
>GID</TT
> check is
   sufficient.  This is supported by means of the <A
HREF="features.safe-mode.html#ini.safe-mode-gid"
>safe_mode_gid</A
> switch. Setting it to
   <TT
CLASS="literal"
>On</TT
> performs the relaxed <TT
CLASS="literal"
>GID</TT
> checking,
   setting it to <TT
CLASS="literal"
>Off</TT
> (the default) performs
   <TT
CLASS="literal"
>UID</TT
> checking.
  </P
><P
>&#13;   If instead of <A
HREF="features.safe-mode.html#ini.safe-mode"
>safe_mode</A
>, you set an 
   <A
HREF="features.safe-mode.html#ini.open-basedir"
>open_basedir</A
> directory then all
   file operations will be limited to files under the specified directory
   For example (Apache httpd.conf example): 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="ini"
>&#60;Directory /docroot&#62;
  php_admin_value open_basedir /docroot 
&#60;/Directory&#62;</PRE
></TD
></TR
></TABLE
>
   If you run the same script.php with this
   <A
HREF="features.safe-mode.html#ini.open-basedir"
>open_basedir</A
> setting
   then this is the result: 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Warning: open_basedir restriction in effect. File is in wrong directory in 
/docroot/script.php on line 2</PRE
></TD
></TR
></TABLE
>
  </P
><P
>&#13;   You can also disable individual functions. Note that the disable_functions 
   directive can not be used outside of the <TT
CLASS="filename"
>php.ini</TT
> file which means that
   you cannot disable functions on a per-virtualhost or per-directory basis
   in your httpd.conf file.
   If we add this to our <TT
CLASS="filename"
>php.ini</TT
> file: 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="ini"
>disable_functions readfile,system</PRE
></TD
></TR
></TABLE
>
   Then we get this output: 
   <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Warning: readfile() has been disabled for security reasons in 
/docroot/script.php on line 2</PRE
></TD
></TR
></TABLE
>
  </P
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