Chromium start-up script doesn't accept argument values with spaces in $CHROMIUM_FLAGS, cause is lack of quotes

[Iuri Chaer]

You can't have arguments with spaces inside CHROMIUM_FLAGS, whatever comes after the first space is going to be interpreted as an URL by the actual chromium binary. Easy repro:

1. Set user's CHROMIUM_FLAGS with an argument containing spaces, eg:
$ echo 'CHROMIUM_FLAGS=--user-agent="A B C"' > .chromium-browser.init

2. Run chromium:
$ /usr/bin/chromium-browser

3. See 2 extra open tabs, one trying to open URL 'B', the other 'C'.

The cause for this funny behavior is the lack of quotes around $CHROMIUM_FLAGS in the script installed in /usr/bin/chromium-browser -- it calls $LIBDIR/$APPNAME $CHROMIUM_FLAGS "$@" by the end of the script. I've tried working around it but couldn't, no amount of escaping and extra quotes seems to help if it's called like that.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "Patch adding quotes to /usr/bin/chromium-browser" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Chad Miller (cmiller)]

I don' think this patch does what you expect.

Try with more than one value in the variable.

CHROMIUM_FLAGS='--user-data-dir=/tmp/cr --user-agent="A B C"'

[Iuri Chaer (iuri-chaer)]

I noticed that last night =( so sad how often I seem to be surprised by how shell expansion works.

Best I could come up with was transform CHROMIUM_FLAGS into an array and use "${CHROMIUM_FLAGS[@]}" in the calls instead. Sorry for the failed patch attempt.

[Chad Miller (cmiller)]

I agree that it's tricky.

The two solutions I can think of is your idea of an array, and assumption
that the variable should go through two levels of interpretation.

The way that makes current scripts and files still work is the latter. It
would go like this:

If there is a special character in the output, it must be quoted or
escaped. Then, special characters must be escaped again.

So, instead of

CHROMIUM_FLAGS="--foo --bar=one\ two"

it would be

CHROMIUM_FLAGS="--foo --bar=one\\\ two"

So, you should be able to

CHROMIUM_FLAGS="--user-agent=Mozilla\\\ 9.0\\\ not\\\ really
--user-data-dir=/path/with/a\\\ space"

On first interpretation, those backslash-character values are interpreted:
backslashbackslash becomes a backslash, and backslashspace becomes a space.

On second interpretation, the one that runs the program, backslashspace is
a space, but not a space that separates parameters. A literal space.

It's not pretty, I know.

On Tue, Nov 10, 2015 at 8:59 AM, Iuri Chaer <email address hidden> wrote:

> I noticed that last night =( so sad how often I seem to be surprised by
> how shell expansion works.
>
> Best I could come up with was transform CHROMIUM_FLAGS into an array and
> use "${CHROMIUM_FLAGS[@]}" in the calls instead. Sorry for the failed
> patch attempt.
>
> --
> You received this bug notification because you are a bug assignee.
> https://bugs.launchpad.net/bugs/1514484
>
> Title:
> Chromium start-up script doesn't accept argument values with spaces in
> $CHROMIUM_FLAGS, cause is lack of quotes
>
> Status in chromium-browser package in Ubuntu:
> Confirmed
>
> Bug description:
> You can't have arguments with spaces inside CHROMIUM_FLAGS, whatever
> comes after the first space is going to be interpreted as an URL by
> the actual chromium binary. Easy repro:
>
> 1. Set user's CHROMIUM_FLAGS with an argument containing spaces, eg:
> $ echo 'CHROMIUM_FLAGS=--user-agent="A B C"' > .chromium-browser.init
>
> 2. Run chromium:
> $ /usr/bin/chromium-browser
>
> 3. See 2 extra open tabs, one trying to open URL 'B', the other 'C'.
>
> The cause for this funny behavior is the lack of quotes around
> $CHROMIUM_FLAGS in the script installed in /usr/bin/chromium-browser
> -- it calls $LIBDIR/$APPNAME $CHROMIUM_FLAGS "$@" by the end of the
> script. I've tried working around it but couldn't, no amount of
> escaping and extra quotes seems to help if it's called like that.
>
> To manage notifications about this bug go to:
>
> https://bugs.launchpad.net/ubuntu/+source/chromium-browser/+bug/1514484/+subscriptions
>

[Iuri Chaer (iuri-chaer)]

Uh, I've tried that, but it keeps splitting the argument values no matter how many slashes I add (they end up interpreted as part of the URL -- for instance, instead of "B" chromium gives me "B/" in the address bar). I've been trying to understand what bash is doing, but it's really eluding me.

[Miyuki Taniguchi (miyuki)]

 Space characters in chromium flags seem to be always parsed even if they are escaped. (Of course, it must be a bug.)

 When splitting all flags in $CHROMIUM_FLAGS by newline and running chromium after IFS=$'\n' , it works.
(And do not escape spaces. like --user-agent=foo bar , not --user-agent="foo bar" or --user-agent=foo\ bar .)

[Nathan Teodosio (nteodosio)]

When a string is put in a shell variable, white-space loses its syntactical information.

Merely quoting $CHROMIUM_FLAGS in the launcher won't do, since we rely on word splitting to split arguments, as noted in #3.

The launcher has a #!/bin/sh shebang, so it's meant as a POSIX compliant shell script. As such, we don't have access to arrays, which are a Korn shell extension, _except_ for the argument list, which can be used as one.

So I see two reasonable options here, and both are backwards-compatible, i.e., won't upset users who are fine with the current state of CHROMIUM_FLAGS.

>> OPTION 1 (already works in the current state of things) <<

Leave the launcher alone and instead instruct the user to abandon CHROMIUM_FLAGS and take advantage of the argument list by writing this ~/.chromium-browser.init:

  set -- --enable-logging=stderr --user-agent='A B C' "$@"

>> OPTION 2 <<

Make these changes in the launcher:

  #!/bin/sh -> #!/bin/bash
  CHROMIUM_FLAGS -> "${CHROMIUM_FLAGS[@]}"

Then ~/.chromium-browser.init would allow for arrays whose elements can contain spaces:

  CHROMIUM_FLAGS=(--enable-logging=stderr --user-agent="A B C")

[Nathan Teodosio (nteodosio)]

My proposed fix to Chromium start-up script wasn't foolproof. One can naturally also export CHROMIUM_FLAGS instead of defining it in ~/chromium.init.

Passing arguments via a variable is a bad idea if one wants both to be reliable with odd input (i.e. accept arguments with spaces (as in the bug report), newlines etc.) and also to be portable, accepting the variable as environment or by sourcing it from a script such as ~/chromium.init.

It's no coincidence that all programs — correct me if I'm wrong — that do allow that kind of thing either don't offer arguments with spaces (less) or allow only one argument per variable (quilt, git, reportbug).

So I'm reverting it and changing the script to detect if CHROMIUM_FLAGS is being used and has any space, then warn on stderr that it will fail for arguments that contain space.