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Groups > linux.debian.bugs.dist > #1070808
| From | Guilhem Moulin <guilhem@debian.org> |
|---|---|
| Newsgroups | linux.debian.bugs.dist |
| Subject | Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files |
| Date | 2021-09-11 22:00 +0200 |
| Message-ID | <CWhkl-6KM-5@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <CWecO-4Y6-15@gated-at.bofh.it> <CWfBT-5Wx-5@gated-at.bofh.it> <CWg4W-660-5@gated-at.bofh.it> <w224W-65h-15@gated-at.bofh.it> <CWg4W-660-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
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On Sat, 11 Sep 2021 at 20:26:57 +0200, Christoph Anton Mitterer wrote: > On Sat, 2021-09-11 at 20:06 +0200, Guilhem Moulin wrote: >> So either I misremembered testing >> this at the time, or something changed meanwhile :-) I'd argue that >> ‘\’ >> is a special character which per documentation “needs to be escaped >> using octal sequences”, so both ‘\n’ and ‘\xHH’ yield unspecified >> behavior, but I guess that can be made explicit. > > Maybe the easiest is simply to write e.g.: > Every field of crypttab is unescaped using printf(1)’s “%b” conversion > specification, which unescapes the \-escapes (\n, \t, \0num, etc.) as > provided by the echo utility. > > Than we're always automatically on the safe side. The use of `printf %b` to decode escape sequences is an internal implementation detail; documenting it would tie our hands for implementation changes… Also there is no guaranty that /bin/sh is dash; don't forget that we also run at initramfs stage where /bin/sh is typically `busybox ash` (but again no guaranty, it can be dash, bash, klibc's sh, or anything else) for which `printf %b` *does* decode \xHH. In my view overspecifying is all but ideal here. >> We assume that unprivileged users do not have write access to >> /etc/crypttab (actually, $TABFILE), keyscripts, or initramfs hook/ >> scripts. Otherwise one can replace askpass with `mail >> me@example.net`, >> append ‘keyscript=gimme_your_password’ to crypttab entries, or simply >> ship compromised executables in the initramfs image. > > I'd still suggest to document that (and not just assume it silently)... > otherwise some smartypants admins might thinkt it's ok to allow users > to just append entries to crypttab in some way they think it would be > secure. Do we warn users not to make /usr/bin, /root or /etc/ld.so.conf writable by unprivileged users? :-) Or not to remove the sticky bit on /tmp? -- Guilhem.
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Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-09 01:00 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-09 01:30 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-09 02:00 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 02:00 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 02:10 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-11 03:20 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 17:20 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-11 18:00 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 18:40 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 20:00 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-27 03:10 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-27 03:40 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-27 17:30 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-27 18:30 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-27 18:50 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-27 19:30 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-27 21:20 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-11 18:10 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 18:40 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-11 20:10 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 20:40 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-11 22:00 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Christoph Anton Mitterer <calestyo@scientia.net> - 2021-09-11 22:10 +0200
Bug#901795: cryptsetup-initramfs: please provide documented shell functions to validate/sanitize cryptroot entries in 3rd party hook files Guilhem Moulin <guilhem@debian.org> - 2021-09-11 22:20 +0200
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