[Bug 1218674] Re: clickpreload doesn't work on armhf

[Loïc Minier]

So the reason fopen64 SEGV is because libselinux actually fopened
/proc/filesystems before libclickpreload's init had run, hence
libclickpreload's fopen64 wrapper would try calling a still NULL
libc_fopen64.

I did an ugly workaround in fopen64 for now to discuss the nicest
approach with Colin, see attached patch.

With the patch, I could click install a .click from a protected dir.

** Summary changed:

- Need to make .click world readable before passing to click install
+ clickpreload doesn't work on armhf

** Patch added: "fopen64.patch"
   https://bugs.launchpad.net/ubuntu/+source/click/+bug/1218674/+attachment/3794542/+files/fopen64.patch

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Title:
  clickpreload doesn't work on armhf

Status in “click” package in Ubuntu:
  New

Bug description:
  Hi,

  TLDR; download-manager only allows downloads to be readable by phablet
  (of course root can too), so that clickpkg user can't read them.

  Installing Click packages from appstore (click scope) in Ubuntu Touch
  images is unreliable.

  I couldn't figure exactly which conditions trigger this, but "pkcon
  install-local some.click" works, and then installation from the scope
  works, however if I install straight from the scope it doens't work.

  I've straced packagekit doing this and spotted some click traceback being written to a .crash which ends with:
  Traceback:
   Traceback (most recent call last):
     File "/usr/bin/click", line 84, in <module>
       sys.exit(main())
     File "/usr/bin/click", line 79, in main
       mod.run(args)
     File "/usr/lib/python3/dist-packages/click/commands/install.py", line 41, in run
       installer.install(package_path, user=options.user)
     File "/usr/lib/python3/dist-packages/click/install.py", line 264, in install
       env=env, **kwargs)
     File "/usr/lib/python3.3/subprocess.py", line 544, in check_call
       raise CalledProcessError(retcode, cmd)
   subprocess.CalledProcessError: Command '['dpkg', '--force-not-root', '--instdir', '/opt/click.ubuntu.com/ar.com.beuno.hello-world/0.6', '--admindir', '/opt/click.ubuntu.com/ar.com.beuno.hello-world/0.6/.click', '--path-exclude', '*/.click/*', '--log', '/opt/click.ubuntu.com/.click/log', '--no-triggers', '--install', '/home/phablet/.local/share/download_manager/{97d4efcf-34bc-4919-a9b4-a1006890128e}/ar.com.beuno.hello-world-0.6.click']' returned non-zero exit status 1

  Which suggests dpkg failing; which I found in the strace started as follows:
  4519  execve("/usr/bin/dpkg", ["dpkg", "--force-not-root", "--instdir", "/opt/click.ubuntu.com/ar.com.beu"..., "--admindir", "/opt/click.ubuntu.com/ar.com.beu"..., "--path-exclude", "*/.click/*", "--log", "/opt/click.ubuntu.com/.click/log", "--no-triggers", "--install", "/home/phablet/.local/share/downl"...], [/* 7 vars */] <unfinished ...>

  then running dpkg-split:
  4520  execve("/usr/bin/dpkg-split", ["dpkg-split", "-Qao", "/opt/click.ubuntu.com/ar.com.beu"..., "/home/phablet/.local/share/downl"...], [/* 8 vars */]) = 0

  but failing to open the package:
  4520  open("/home/phablet/.local/share/download_manager/{8ec430e5-a192-493a-bdb6-478fffcb7ab1}/ar.com.beuno.hello-world-0.6.click", O_RDONLY|O_LARGEFILE) = -1 EACCES (Permission denied)
  4520  write(2, "dpkg-split: error: unable to rea"..., 183) = 183

  Immediately before, one can see:
  4520  geteuid32()                       = 106

  which was set when launching dpkg:
  4519  setresgid32(107, 107, 107)        = 0
  4519  setresuid32(106, 106, 106)        = 0
  4519  getresuid32([106], [106], [106])  = 0
  4519  getresgid32([107], [107], [107])  = 0

  Indeed, click install had switched to the clickpkg user:
  clickpkg:x:106:107::/nonexistent:/bin/false

  So the problem is that .clicks may only be read by phablet user or
  root, but not by clickpkg.

  Cheers,

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