system password storages

should fix github issue #14

setup.py

@@ -25,5 +25,6 @@ setup(
     entry_points={
         'console_scripts': ['vdirsyncer = vdirsyncer.cli:main']
     },
-    install_requires=['argvard', 'requests', 'lxml']
+    install_requires=['argvard', 'requests', 'lxml'],
+    extras_require={'keyring': ['keyring']}
 )

vdirsyncer/storage/http.py

@@ -12,7 +12,7 @@ import requests
 import urlparse
 import hashlib
 from .base import Storage, Item
-from vdirsyncer.utils import expand_path
+from vdirsyncer.utils import expand_path, get_password
 
 
 def split_collection(text):
@@ -81,6 +81,9 @@ class HttpStorageBase(Storage):
         '''
         super(HttpStorageBase, self).__init__(**kwargs)
 
+        if username and not password:
+            password = get_password(username, url)
+
         self._settings = {
             'verify': prepare_verify(verify),
             'auth': prepare_auth(auth, username, password)

vdirsyncer/utils.py

@@ -9,6 +9,7 @@
 
 import os
 
+import vdirsyncer.log
 
 def expand_path(p):
     p = os.path.expanduser(p)
@@ -39,3 +40,78 @@ def parse_options(items):
         except ValueError:
             pass
         yield key, value
+
+
+def get_password(username, resource):
+    """tries to access saved password or asks user for it
+
+    will try the following in this order:
+        1. read password from netrc (and only the password, username
+           in netrc will be ignored)
+        2. read password from keyring (keyring needs to be installed)
+        3a ask user for the password
+         b save in keyring if installed and user agrees
+
+    :param username: user's name on the server
+    :type username: str/unicode
+    :param resource: a resource to which the user has access via password,
+                     it will be shortened to just the hostname. It is assumed
+                     that each unique username/hostname combination only ever
+                     uses the same password.
+    :type resource: str/unicode
+    :return: password
+    :rtype: str/unicode
+
+
+    """
+    import getpass
+    from netrc import netrc
+    try:
+        from urlparse import urlsplit
+    except ImportError:
+        from urllib.parse import urlsplit
+
+    sync_logger = vdirsyncer.log.get('sync')
+
+    # XXX is it save to asume that a password is always the same for
+    # any given (hostname, username) combination?
+    hostname = urlsplit(resource).hostname
+
+    # netrc
+    try:
+        auths = netrc().authenticators(hostname)
+        # auths = (user, password)
+    except IOError:
+        pass
+    else:
+        sync_logger.debug("Read password for user {0} on {1} in .netrc".format(
+            auths[0], hostname))
+        return auths[1]
+
+    # keyring
+    try:
+        import keyring
+    except ImportError:
+        keyring = None
+    else:
+        password = keyring.get_password(
+            'vdirsyncer:' + hostname, username)
+        if password is not None:
+            sync_logger.debug("Got password for user {0}@{1} from keyring".format(
+                username, hostname))
+            return password
+
+    if password is None:
+        prompt = 'Server password {0}@{1}: '.format(username, hostname)
+        password = getpass.getpass(prompt=prompt)
+
+    if keyring:
+        answer = 'x'
+        while answer.lower() not in ['', 'y', 'n']:
+            prompt = 'Save this password in the keyring? [y/N] '
+            answer = raw_input(prompt)
+        if answer.lower() == 'y':
+            password = keyring.set_password(
+                'vdirsyncer:' + hostname, username, password)
+
+    return password