[Bug 1747711] Re: file mis-identifies modern executables as application/x-sharedlib

[Brian Murray]

It is also an issue on bionic:

 $ schroot -u root -c bionic-amd64
(bionic-amd64)root at impulse:/tmp# echo "int main() { return 0; }" > foo.c
(bionic-amd64)root at impulse:/tmp# gcc -o foo foo.c
(bionic-amd64)root at impulse:/tmp# file foo
foo: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=5222fe7f5f12ee8d286b84f93c981cab98ad382a, not stripped

But not on xenial:

 $ schroot -u root -c xenial-amd64
(xenial-amd64)root at impulse:/tmp# echo "int main() { return 0; }" > foo.c
(xenial-amd64)root at impulse:/tmp# gcc -o foo foo.c
(xenial-amd64)root at impulse:/tmp# file foo
foo: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=5a079b5be569b3e0527b9685f1c7811fb193d37c, not stripped

Using gcc from xenial and file from bionic though the file is identified
as an executable so I don't think its file.

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Title:
  file mis-identifies modern executables as application/x-sharedlib

Status in file package in Ubuntu:
  New

Bug description:
  file doesn't recognize modern PIE (Position Independent Executable)
  x86 executables as such, reporting them as “application/x-sharedlib”.
  Consequently, only non-PIE executables can be opened in graphical file
  managers such as nautilus. This may cause a minor (?) security risk if
  a commonly-published workaround is attempted.

  Expected behaviour:

      $ echo "int main() { return 0; }" > foo.c
      $ gcc -o foo foo.c
      $ file foo
      foo: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=6e7749f995a89a53f74ec29d3c16fcf3f56be90f, not stripped
      $ file --mime-type foo
      foo: application/x-executable

  Actual behaviour:

      $ echo "int main() { return 0; }" > foo.c
      $ gcc -o foo foo.c
      $ file foo
      foo: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=6e7749f995a89a53f74ec29d3c16fcf3f56be90f, not stripped
      $ file --mime-type foo
      foo: application/x-sharedlib

  Workaround (unsafe?):

      $ echo "int main() { return 0; }" > foo.c
      $ gcc -o foo-nopie foo.c -no-pie
      $ file foo-nopie
      foo-nopie: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=3eb8c581f43c19997e3c828f5a9730dbdc794470, not stripped
      $ file --mime-type foo-nopie
      foo-nopie: application/x-executable

  gcc now defaults to building with PIE enabled for security reasons.

  Also affects: nautilus (and likely other graphical file managers like
  those on Lubuntu) - because nautilus uses mime-type to determine if a
  file is executable, double-click to run a program no longer works.

  Also noted on: Gnome Bugs -
  https://bugzilla.gnome.org/show_bug.cgi?id=737849 (2014) - before PIE
  became the default build option.

  This may be an upstream issue. This may not affect architectures
  outside x86.*

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: file 1:5.32-1
  ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13
  Uname: Linux 4.13.0-32-generic x86_64
  ApportVersion: 2.20.7-0ubuntu3.7
  Architecture: amd64
  CurrentDesktop: GNOME
  Date: Tue Feb  6 11:21:20 2018
  InstallationDate: Installed on 2017-05-11 (270 days ago)
  InstallationMedia: Ubuntu-GNOME 17.04 "Zesty Zapus" - Release amd64 (20170412)
  SourcePackage: file
  UpgradeStatus: Upgraded to artful on 2017-10-21 (108 days ago)

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