ui: merge into a single module

libagent/device/ui.py

@@ -0,0 +1,123 @@
+"""UIs for PIN/passphrase entry."""
+
+import logging
+import os
+import subprocess
+
+from ..gpg import agent
+
+log = logging.getLogger(__name__)
+
+
+class UI(object):
+    """UI for PIN/passphrase entry (for TREZOR devices)."""
+
+    def __init__(self, device_type, config=None):
+        """C-tor."""
+        default_pinentry = 'pinentry'  # by default, use GnuPG pinentry tool
+        if config is None:
+            config = {}
+        self.pin_entry_binary = config.get('pin_entry_binary',
+                                           default_pinentry)
+        self.passphrase_entry_binary = config.get('passphrase_entry_binary',
+                                                  default_pinentry)
+        self.options_getter = create_default_options_getter()
+        self.device_name = device_type.__name__
+
+    def get_pin(self):
+        """Ask the user for (scrambled) PIN."""
+        description = (
+            'Use the numeric keypad to describe number positions.\n'
+            'The layout is:\n'
+            '    7 8 9\n'
+            '    4 5 6\n'
+            '    1 2 3')
+        return interact(
+            title='{} PIN'.format(self.device_name),
+            prompt='PIN:',
+            description=description,
+            binary=self.pin_entry_binary,
+            options=self.options_getter())
+
+    def get_passphrase(self):
+        """Ask the user for passphrase."""
+        return interact(
+            title='{} passphrase'.format(self.device_name),
+            prompt='Passphrase:',
+            description=None,
+            binary=self.passphrase_entry_binary,
+            options=self.options_getter())
+
+
+def create_default_options_getter():
+    """Return current TTY and DISPLAY settings for GnuPG pinentry."""
+    options = []
+    try:
+        ttyname = subprocess.check_output(args=['tty']).strip()
+        options.append(b'ttyname=' + ttyname)
+    except subprocess.CalledProcessError as e:
+        log.warning('no TTY found: %s', e)
+
+    display = os.environ.get('DISPLAY')
+    if display is not None:
+        options.append('display={}'.format(display).encode('ascii'))
+    else:
+        log.warning('DISPLAY not defined')
+
+    log.info('using %s for pinentry options', options)
+    return lambda: options
+
+
+def write(p, line):
+    """Send and flush a single line to the subprocess' stdin."""
+    log.debug('%s <- %r', p.args, line)
+    p.stdin.write(line)
+    p.stdin.flush()
+
+
+def expect(p, prefixes):
+    """Read a line and return it without required prefix."""
+    resp = p.stdout.readline()
+    log.debug('%s -> %r', p.args, resp)
+    for prefix in prefixes:
+        if resp.startswith(prefix):
+            return resp[len(prefix):]
+    raise ValueError('Unexpected response: {}'.format(resp))
+
+
+def interact(title, description, prompt, binary, options):
+    """Use GPG pinentry program to interact with the user."""
+    p = subprocess.Popen(args=[binary],
+                         stdin=subprocess.PIPE,
+                         stdout=subprocess.PIPE,
+                         env=os.environ)
+    expect(p, [b'OK'])
+
+    title = agent.serialize(title.encode('ascii'))
+    write(p, b'SETTITLE ' + title + b'\n')
+    expect(p, [b'OK'])
+
+    if description:
+        description = agent.serialize(description.encode('ascii'))
+        write(p, b'SETDESC ' + description + b'\n')
+        expect(p, [b'OK'])
+
+    if prompt:
+        prompt = agent.serialize(prompt.encode('ascii'))
+        write(p, b'SETPROMPT ' + prompt + b'\n')
+        expect(p, [b'OK'])
+
+    log.debug('setting %d options', len(options))
+    for opt in options:
+        write(p, b'OPTION ' + opt + b'\n')
+        expect(p, [b'OK', b'ERR'])
+
+    write(p, b'GETPIN\n')
+    pin = expect(p, [b'OK', b'D '])
+
+    p.communicate()  # close stdin and wait for the process to exit
+    exit_code = p.wait()
+    if exit_code:
+        raise subprocess.CalledProcessError(exit_code, binary)
+
+    return pin.decode('ascii').strip()