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Diffstat (limited to 'Doc/library/subprocess.rst')
| -rw-r--r-- | Doc/library/subprocess.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst index 7402ad5..c490203 100644 --- a/Doc/library/subprocess.rst +++ b/Doc/library/subprocess.rst @@ -75,6 +75,24 @@ This module defines one class called :class:`Popen`: Popen(['/bin/sh', '-c', args[0], args[1], ...]) + .. warning:: + + Executing shell commands that incorporate unsanitized input from an + untrusted source makes a program vulnerable to `shell injection + <http://en.wikipedia.org/wiki/Shell_injection#Shell_injection>`_, + a serious security flaw which can result in arbitrary command execution. + For this reason, the use of *shell=True* is **strongly discouraged** in cases + where the command string is constructed from external input:: + + >>> from subprocess import call + >>> filename = input("What file would you like to display?\n") + What file would you like to display? + non_existent; rm -rf / # + >>> call("cat " + filename, shell=True) # Uh-oh. This will end badly... + + *shell=False* does not suffer from this vulnerability; the above Note may be + helpful in getting code using *shell=False* to work. + On Windows: the :class:`Popen` class uses CreateProcess() to execute the child program, which operates on strings. If *args* is a sequence, it will be converted to a string using the :meth:`list2cmdline` method. Please note that |