Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 19 Oct 2012 15:04:03 -0700 | Subject | Re: RFC: sign the modules at install time |
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On Fri, Oct 19, 2012 at 12:58 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > Tssk. I fixed it up, and now it works-for-me(tm), but some perl person > probably really should try to make that sign-file and x509keyid merge. > My fix made the thing even slower, doing two extra "wc -c" invocations > since it can't do "${#..}" expansion due to the locale problem.
Hmm. I haven't seen this breakage personally yet, but looking more at Rusty's last changes I'm pretty sure my fixes are potentially not sufficient.
In particular, this line from Rusty's sign-file script simplification makes me worry:
KEYID="`perl $keyid_script $x509 keyid`"
and the problem is that the 'keyid' is a binary blob.
And I'm pretty damn sure that assigning random binary data to shell variables is going to break eventually. In particular, I tested NUL characters, and bash is not happy about doing things like
a="`echo -en '\000'`"
and 'a' ends up empty, not containing a one-byte string containing a NUL character. Not to mention that even if the shell were to handle this correctly, if you do
echo -n "$a"
then even *if* the shell remembered that 'a' contains one NUL character, when it then executes the 'echo' binary, that will certainly not be able to handle it. With a built-in 'echo' it _could_ work, with an external one it fundamentally could not. NUL is special, and terminates strings at execve(). You cannot have NUL bytes in arguments.
Of course, I don't know the rules for x509 key id blobs. Maybe they aren't allowed to contain NUL anyway?
Possible solutions:
- Linus is a worry-wart, and key id's never contain NUL.
- somebody with the appropriate perl-fu does the perl conversion, and keeps it all in perl.
- somebody with (slightly less) perl-fu makes the x509 keyid_script return a quoted string, so that we can save that *quoted* version for the shell interatction (perhaps in a similar format that we now use for the "prologue" variable, ie just a list of hex bytes)
otherwise we need to go back to putting the binary blob in a file (which shell won't corrupt).
Rusty, David?
Linus
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