Check that GnuPG key import was successful.

[isislovecruft]

Rather than checking the GnuPG process exit code, a more robust way to
handle determining whether or not a GnuPG process behaved as was
intended is to check GnuPG's status-fd output. 0

In the case of key import, the particular status-fd flag we're looking
for is IMPORT_OK followed by a "reason", then the expected
fingerprint. 1 Because the "reason"s are integers which may be ORed,
and we are never expecting private keys to be within the file, we can
assume the reason to be [0, 15] inclusive.

While it's not strictly necessary to hardcode Erinn's key fingerprint
within the code because the keyfiles are safely distributed along with
the source code, doing so adds a simple defense-in-depth mechanism for
the unlikely case that a user's torbrowser-launcher package/source
download was compromised. As such, and because it was a trivial
addition which will also assist with checking that a signature was made
by the key with the expected fingerprint 2, I've gone ahead and added
a common.fingerprints dictionary whose keys match the names of the
common.paths keyfile for their respective key (i.e. the fingerprint
for common.paths['erinn_key'] is stored at
common.fingerprints['erinn_key']) in order to facilitate extensibility
in the event that torbrowser-launcher should add new keyfiles in the
future. This may be removed, if undesirable.

• ADD common.gnupg_import_ok_pattern, a compiled regex for
  determining if a key import was successful.
• ADD new class attribute, common.Common.fingerprints for storing
  fingerprints.
• ADD new method, common.Common.import_key_and_check_status(), which
  imports a GnuPG key, and then checks that the key was successfully
  imported.
• CHANGE common.Common.import_keys() method to make adding
  new/additional keys easier.
• FIXES check gpg exit code after gpg key import #137

[isislovecruft]

Ah, someone should also check if this works on Windows. Sometimes parts of the Python subprocess module hate on Windows users.

[micahflee]

Thank you @isislovecruft! Sorry for taking so long, reviewing and merging now.

[micahflee]

If I delete all of the TBL files (rm -r ~/.local/share/torbrowser/ ~/.cache/torbrowser/ ~/.config/torbrowser/) and then run torbrowser-launcher for the first time, I get this:

Creating GnuPG homedir /home/micah/.local/share/torbrowser/gnupg_homedir
Importing keys
Could not import key with fingerprint: 8738A680B84B3031A630F2DB416F061063FEE659.
Not all keys were imported successfully!

However the key does indeed get imported successfully, and it verifies the signature successfully after downloading TBB.

If I run torbrowser-launcher a second time I get:

Importing keys
Successfully imported all keys.

It looks like when I run it just after deleting all of the TBL files, this is the output:

gpg: keyring `/home/micah/.local/share/torbrowser/gnupg_homedir/secring.gpg' created
gpg: keyring `/home/micah/.local/share/torbrowser/gnupg_homedir/pubring.gpg' created
gpg: /home/micah/.local/share/torbrowser/gnupg_homedir/trustdb.gpg: trustdb created
gpg: key 63FEE659: public key "Erinn Clark <erinn@torproject.org>" imported
[GNUPG:] IMPORTED 416F061063FEE659 Erinn Clark <erinn@torproject.org>
[GNUPG:] IMPORT_OK 1 8738A680B84B3031A630F2DB416F061063FEE659
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
[GNUPG:] IMPORT_RES 1 0 1 1 0 0 0 0 0 0 0 0 0 0

And when I run it a second time, this is the output:

[GNUPG:] IMPORT_OK 0 8738A680B84B3031A630F2DB416F061063FEE659
gpg: key 63FEE659: "Erinn Clark <erinn@torproject.org>" not changed
gpg: Total number processed: 1
gpg:              unchanged: 1
[GNUPG:] IMPORT_RES 1 0 0 0 1 0 0 0 0 0 0 0 0 0

I think the regex is only checking the first line of output, not the first "[GNUPG:]" line.

[micahflee]

A year and a half late merging a pull request is better than never, right?