2023-01-22 18:11:10 +00:00
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# Copyright 2023 Oliver Smith
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2020-02-20 20:07:28 +00:00
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# SPDX-License-Identifier: GPL-3.0-or-later
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2017-05-26 20:08:45 +00:00
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import pmb.chroot.root
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Properly escape commands in pmb.chroot.user() (#1316)
## Introduction
In #1302 we noticed that `pmb.chroot.user()` does not escape commands
properly: When passing one string with spaces, it would pass them as
two strings to the chroot. The use case is passing a description with
a space inside to `newapkbuild` with `pmboostrap newapkbuild`.
This is not a security issue, as we don't pass strings from untrusted
input to this function.
## Functions for running commands in pmbootstrap
To put the rest of the description in context: We have four high level
functions that run commands:
* `pmb.helpers.run.user()`
* `pmb.helpers.run.root()`
* `pmb.chroot.root()`
* `pmb.chroot.user()`
In addition, one low level function that the others invoke:
* `pmb.helpers.run.core()`
## Flawed test case
The issue described above did not get detected for so long, because we
have a test case in place since day one, which verifies that all of the
functions above escape everything properly:
* `test/test_shell_escape.py`
So the test case ran a given command through all these functions, and
compared the result each time. However, `pmb.chroot.root()`
modified the command variable (passed by reference) and did the
escaping already, which means `pmb.chroot.user()` running directly
afterwards only returns the right output when *not* doing any escaping.
Without questioning the accuracy of the test case, I've escaped
commands and environment variables with `shlex.quote()` *before*
passing them to `pmb.chroot.user()`. In retrospective this does not
make sense at all and is reverted with this commit.
## Environment variables
By coincidence, we have only passed custom environment variables to
`pmb.chroot.user()`, never to the other high level functions. This only
worked, because we did not do any escaping and the passed line gets
executed as shell command:
```
$ MYENV=test echo test2
test 2
```
If it was properly escaped as one shell command:
```
$ 'MYENV=test echo test2'
sh: MYENV=test echo test2: not found
```
So doing that clearly doesn't work anymore. I have added a new `env`
parameter to `pmb.chroot.user()` (and to all other high level functions
for consistency), where environment variables can be passed as a
dictionary. Then the function knows what to do and we end up with
properly escaped commands and environment variables.
## Details
* Add new `env` parameter to all high level command execution functions
* New `pmb.helpers.run.flat_cmd()` function, that takes a command as
list and environment variables as dict, and creates a properly escaped
flat string from the input.
* Use that function for proper escaping in all high level exec funcs
* Don't escape commands *before* passing them to `pmb.chroot.user()`
* Describe parameters of the command execution functions
* `pmbootstrap -v` writes the exact command to the log that was
executed (in addition to the simplified form we always write down for
readability)
* `test_shell_escape.py`: verify that the command passed by reference
has not been modified, add a new test for strings with spaces, add
tests for new function `pmb.helpers.run.flat_cmd()`
* Remove obsolete commend in `pmb.chroot.distccd` about environment
variables, because we don't use any there anymore
* Add `TERM=xterm` to default environment variables in the chroot,
so running ncurses applications like `menuconfig` and `nano` works out of
the box
2018-03-10 22:58:39 +00:00
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import pmb.helpers.run
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2017-05-26 20:08:45 +00:00
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2018-07-14 01:13:28 +00:00
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def user(args, cmd, suffix="native", working_dir="/", output="log",
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output_return=False, check=None, env={}, auto_init=True):
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2017-05-26 20:08:45 +00:00
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"""
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Properly escape commands in pmb.chroot.user() (#1316)
## Introduction
In #1302 we noticed that `pmb.chroot.user()` does not escape commands
properly: When passing one string with spaces, it would pass them as
two strings to the chroot. The use case is passing a description with
a space inside to `newapkbuild` with `pmboostrap newapkbuild`.
This is not a security issue, as we don't pass strings from untrusted
input to this function.
## Functions for running commands in pmbootstrap
To put the rest of the description in context: We have four high level
functions that run commands:
* `pmb.helpers.run.user()`
* `pmb.helpers.run.root()`
* `pmb.chroot.root()`
* `pmb.chroot.user()`
In addition, one low level function that the others invoke:
* `pmb.helpers.run.core()`
## Flawed test case
The issue described above did not get detected for so long, because we
have a test case in place since day one, which verifies that all of the
functions above escape everything properly:
* `test/test_shell_escape.py`
So the test case ran a given command through all these functions, and
compared the result each time. However, `pmb.chroot.root()`
modified the command variable (passed by reference) and did the
escaping already, which means `pmb.chroot.user()` running directly
afterwards only returns the right output when *not* doing any escaping.
Without questioning the accuracy of the test case, I've escaped
commands and environment variables with `shlex.quote()` *before*
passing them to `pmb.chroot.user()`. In retrospective this does not
make sense at all and is reverted with this commit.
## Environment variables
By coincidence, we have only passed custom environment variables to
`pmb.chroot.user()`, never to the other high level functions. This only
worked, because we did not do any escaping and the passed line gets
executed as shell command:
```
$ MYENV=test echo test2
test 2
```
If it was properly escaped as one shell command:
```
$ 'MYENV=test echo test2'
sh: MYENV=test echo test2: not found
```
So doing that clearly doesn't work anymore. I have added a new `env`
parameter to `pmb.chroot.user()` (and to all other high level functions
for consistency), where environment variables can be passed as a
dictionary. Then the function knows what to do and we end up with
properly escaped commands and environment variables.
## Details
* Add new `env` parameter to all high level command execution functions
* New `pmb.helpers.run.flat_cmd()` function, that takes a command as
list and environment variables as dict, and creates a properly escaped
flat string from the input.
* Use that function for proper escaping in all high level exec funcs
* Don't escape commands *before* passing them to `pmb.chroot.user()`
* Describe parameters of the command execution functions
* `pmbootstrap -v` writes the exact command to the log that was
executed (in addition to the simplified form we always write down for
readability)
* `test_shell_escape.py`: verify that the command passed by reference
has not been modified, add a new test for strings with spaces, add
tests for new function `pmb.helpers.run.flat_cmd()`
* Remove obsolete commend in `pmb.chroot.distccd` about environment
variables, because we don't use any there anymore
* Add `TERM=xterm` to default environment variables in the chroot,
so running ncurses applications like `menuconfig` and `nano` works out of
the box
2018-03-10 22:58:39 +00:00
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Run a command inside a chroot as "user". We always use the BusyBox
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implementation of 'su', because other implementations may override the PATH
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environment variable (#1071).
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:param env: dict of environment variables to be passed to the command, e.g.
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{"JOBS": "5"}
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2018-07-14 01:13:28 +00:00
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:param auto_init: automatically initialize the chroot
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See pmb.helpers.run_core.core() for a detailed description of all other
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arguments and the return value.
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2017-05-26 20:08:45 +00:00
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"""
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2018-10-25 05:18:43 +00:00
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if "HOME" not in env:
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env["HOME"] = "/home/pmos"
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Properly escape commands in pmb.chroot.user() (#1316)
## Introduction
In #1302 we noticed that `pmb.chroot.user()` does not escape commands
properly: When passing one string with spaces, it would pass them as
two strings to the chroot. The use case is passing a description with
a space inside to `newapkbuild` with `pmboostrap newapkbuild`.
This is not a security issue, as we don't pass strings from untrusted
input to this function.
## Functions for running commands in pmbootstrap
To put the rest of the description in context: We have four high level
functions that run commands:
* `pmb.helpers.run.user()`
* `pmb.helpers.run.root()`
* `pmb.chroot.root()`
* `pmb.chroot.user()`
In addition, one low level function that the others invoke:
* `pmb.helpers.run.core()`
## Flawed test case
The issue described above did not get detected for so long, because we
have a test case in place since day one, which verifies that all of the
functions above escape everything properly:
* `test/test_shell_escape.py`
So the test case ran a given command through all these functions, and
compared the result each time. However, `pmb.chroot.root()`
modified the command variable (passed by reference) and did the
escaping already, which means `pmb.chroot.user()` running directly
afterwards only returns the right output when *not* doing any escaping.
Without questioning the accuracy of the test case, I've escaped
commands and environment variables with `shlex.quote()` *before*
passing them to `pmb.chroot.user()`. In retrospective this does not
make sense at all and is reverted with this commit.
## Environment variables
By coincidence, we have only passed custom environment variables to
`pmb.chroot.user()`, never to the other high level functions. This only
worked, because we did not do any escaping and the passed line gets
executed as shell command:
```
$ MYENV=test echo test2
test 2
```
If it was properly escaped as one shell command:
```
$ 'MYENV=test echo test2'
sh: MYENV=test echo test2: not found
```
So doing that clearly doesn't work anymore. I have added a new `env`
parameter to `pmb.chroot.user()` (and to all other high level functions
for consistency), where environment variables can be passed as a
dictionary. Then the function knows what to do and we end up with
properly escaped commands and environment variables.
## Details
* Add new `env` parameter to all high level command execution functions
* New `pmb.helpers.run.flat_cmd()` function, that takes a command as
list and environment variables as dict, and creates a properly escaped
flat string from the input.
* Use that function for proper escaping in all high level exec funcs
* Don't escape commands *before* passing them to `pmb.chroot.user()`
* Describe parameters of the command execution functions
* `pmbootstrap -v` writes the exact command to the log that was
executed (in addition to the simplified form we always write down for
readability)
* `test_shell_escape.py`: verify that the command passed by reference
has not been modified, add a new test for strings with spaces, add
tests for new function `pmb.helpers.run.flat_cmd()`
* Remove obsolete commend in `pmb.chroot.distccd` about environment
variables, because we don't use any there anymore
* Add `TERM=xterm` to default environment variables in the chroot,
so running ncurses applications like `menuconfig` and `nano` works out of
the box
2018-03-10 22:58:39 +00:00
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flat_cmd = pmb.helpers.run.flat_cmd(cmd, env=env)
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cmd = ["busybox", "su", "pmos", "-c", flat_cmd]
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2018-07-14 01:13:28 +00:00
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return pmb.chroot.root(args, cmd, suffix, working_dir, output,
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output_return, check, {}, auto_init)
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2017-10-12 20:08:10 +00:00
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def exists(args, username, suffix="native"):
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"""
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Checks if username exists in the system
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:param username: User name
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:returns: bool
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"""
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output = pmb.chroot.root(args, ["getent", "passwd", username],
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2018-07-14 01:13:28 +00:00
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suffix, output_return=True, check=False)
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return len(output) > 0
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