From d52f295326caa93b0580b458cbcd7974dcc76791 Mon Sep 17 00:00:00 2001
From: Roman Zeyde <roman.zeyde@gmail.com>
Date: Thu, 2 Nov 2017 17:10:09 +0200
Subject: [PATCH] gpg: use shutil.which() for Python 3

---
 libagent/gpg/__init__.py |  3 +--
 libagent/gpg/keyring.py  | 20 +++++++++++---------
 libagent/util.py         | 11 +++++++++++
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/libagent/gpg/__init__.py b/libagent/gpg/__init__.py
index 0a10e21..24f2523 100644
--- a/libagent/gpg/__init__.py
+++ b/libagent/gpg/__init__.py
@@ -129,8 +129,7 @@ def run_init(device_type, args):
     check_call(['mkdir', '-p', homedir])
     check_call(['chmod', '700', homedir])
 
-    agent_path = check_output(['which', '{}-gpg-agent'.format(device_name)])
-    agent_path = agent_path.strip()
+    agent_path = util.which('{}-gpg-agent'.format(device_name))
 
     # Prepare GPG configuration file
     with open(os.path.join(homedir, 'gpg.conf'), 'w') as f:
diff --git a/libagent/gpg/keyring.py b/libagent/gpg/keyring.py
index 76c8090..cd73d99 100644
--- a/libagent/gpg/keyring.py
+++ b/libagent/gpg/keyring.py
@@ -16,10 +16,11 @@ log = logging.getLogger(__name__)
 
 def get_agent_sock_path(env=None, sp=subprocess):
     """Parse gpgconf output to find out GPG agent UNIX socket path."""
-    output = sp.check_output(['gpgconf', '--list-dirs'], env=env)
+    args = [util.which('gpgconf'), '--list-dirs']
+    output = sp.check_output(args=args, env=env)
     lines = output.strip().split(b'\n')
     dirs = dict(line.split(b':', 1) for line in lines)
-    log.debug('gpgconf --list-dirs: %s', dirs)
+    log.debug('%s: %s', args, dirs)
     return dirs[b'agent-socket']
 
 
@@ -179,22 +180,23 @@ def sign_digest(sock, keygrip, digest, sp=subprocess, environ=None):
 
 def get_gnupg_components(sp=subprocess):
     """Parse GnuPG components' paths."""
-    output = sp.check_output(['gpgconf', '--list-components'])
+    output = sp.check_output([util.which('gpgconf'), '--list-components'])
     components = dict(re.findall('(.*):.*:(.*)', output.decode('ascii')))
     log.debug('gpgconf --list-components: %s', components)
     return components
 
 
+@util.memoize
 def get_gnupg_binary(sp=subprocess):
     """Starting GnuPG 2.2.x, the default installation uses `gpg`."""
     return get_gnupg_components(sp=sp)['gpg']
 
 
-def gpg_command(args, env=None, sp=subprocess):
+def gpg_command(args, env=None):
     """Prepare common GPG command line arguments."""
     if env is None:
         env = os.environ
-    cmd = [get_gnupg_binary(sp=sp)]
+    cmd = [get_gnupg_binary()]
     homedir = env.get('GNUPGHOME')
     if homedir:
         cmd.extend(['--homedir', homedir])
@@ -203,14 +205,14 @@ def gpg_command(args, env=None, sp=subprocess):
 
 def get_keygrip(user_id, sp=subprocess):
     """Get a keygrip of the primary GPG key of the specified user."""
-    args = gpg_command(['--list-keys', '--with-keygrip', user_id], sp=sp)
+    args = gpg_command(['--list-keys', '--with-keygrip', user_id])
     output = sp.check_output(args).decode('ascii')
     return re.findall(r'Keygrip = (\w+)', output)[0]
 
 
 def gpg_version(sp=subprocess):
     """Get a keygrip of the primary GPG key of the specified user."""
-    args = gpg_command(['--version'], sp=sp)
+    args = gpg_command(['--version'])
     output = sp.check_output(args)
     line = output.split(b'\n')[0]  # b'gpg (GnuPG) 2.1.11'
     return line.split(b' ')[-1]  # b'2.1.11'
@@ -218,7 +220,7 @@ def gpg_version(sp=subprocess):
 
 def export_public_key(user_id, env=None, sp=subprocess):
     """Export GPG public key for specified `user_id`."""
-    args = gpg_command(['--export', user_id], sp=sp)
+    args = gpg_command(['--export', user_id])
     result = sp.check_output(args=args, env=env)
     if not result:
         log.error('could not find public key %r in local GPG keyring', user_id)
@@ -228,7 +230,7 @@ def export_public_key(user_id, env=None, sp=subprocess):
 
 def export_public_keys(env=None, sp=subprocess):
     """Export all GPG public keys."""
-    args = gpg_command(['--export'], sp=sp)
+    args = gpg_command(['--export'])
     result = sp.check_output(args=args, env=env)
     if not result:
         raise KeyError('No GPG public keys found at env: {!r}'.format(env))
diff --git a/libagent/util.py b/libagent/util.py
index c10b0b6..82e60ee 100644
--- a/libagent/util.py
+++ b/libagent/util.py
@@ -4,6 +4,7 @@ import contextlib
 import functools
 import io
 import logging
+import shutil
 import struct
 
 log = logging.getLogger(__name__)
@@ -213,3 +214,13 @@ def memoize(func):
             return result
 
     return wrapper
+
+
+@memoize
+def which(cmd):
+    """Return full path to specified command, or raise OSError if missing."""
+    full_path = shutil.which(cmd)
+    if full_path is None:
+        raise OSError('Cannot find {!r} in $PATH'.format(cmd))
+    log.debug('which %r => %r', cmd, full_path)
+    return full_path