## 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
I've replaced all instances in the code of `os.path.abspath`
with `os.path.realpath`, as this does the same as `abspath`
plus resolving symlinks.
See also: https://stackoverflow.com/a/40311142
TLDR: Always rebuild/install packages when something changed when executing "pmbootstrap install/initfs/flash", more speed in dependency resolution.
---
pmbootstrap has already gotten some support for "timestamp based rebuilds", which modifies the logic for when packages should be rebuilt. It doesn't only consider packages outdated with old pkgver/pkgrel combinations, but also packages, where a source file has a newer timestamp, than the built package has.
I've found out, that this can lead to more rebuilds than expected. For example, when you check out the pmbootstrap git repository again into another folder, although you have already built packages. Then all files have the timestamp of the checkout, and the packages will appear to be outdated. While this is not largely a concern now, this will become a problem once we have a binary package repository, because then the packages from the binary repo will always seem to be outdated, if you just freshly checked out the repository.
To combat this, git gets asked if the files from the aport we're looking at are in sync with upstream, or not. Only when the files are not in sync with upstream and the timestamps of the sources are newer, a rebuild gets triggered from now on.
In case this logic should fail, I've added an option during "pmbootstrap init" where you can enable or disable the "timestamp based rebuilds" option.
In addition to that, this commit also works on fixing #120: packages do not get updated in "pmbootstrap install" after they have been rebuilt. For this to work, we specify all packages explicitly for abuild, instead of letting abuild do the resolving. This feature will also work with the "timestamp based rebuilds".
This commit also fixes the working_dir argument in pmb.helpers.run.user, which was simply ignored before.
Finally, the performance of the dependency resolution is faster again (when compared to the current version in master), because the parsed apkbuilds and finding the aport by pkgname gets cached during one pmbootstrap call (in args.cache, which also makes it easy to put fake data there in testcases).
The new dependency resolution code can output lots of verbose messages for debugging by specifying the `-v` parameter. The meaning of that changed, it used to output the file names where log messages come from, but no one seemed to use that anyway.
* automatically find the chroot binary on Debian, even if it is not
in the user's PATH
* don't use subprocess.run anymore (remove related testcase, that explicitly
checked for subprocess.run usage, and used recursive globbing, another
post 3.4 Python feature, for the checks. A similar case can be added in the
future, but right now it's more important to get Debian 3.4 working and all
PRs are reviewed anyway.)
* pytest fixtures: don't use the newer "yield" feature, as this is only
supported in a newer version of pytest, than provided on Debian Jessie
From manually testing, most stuff works in Debian Jessie. However, the
testsuite does not run through - creating an empty .tar.gz with Python
fails for some reason (this is done in test_apk_static.py).
Oliver Smith