Add pass authenticator

CHANGELOG.md

@@ -25,6 +25,7 @@ ambiguous situations.
 ### Added
 - Download of page descriptions
 - Forum download support
+- `pass` authenticator
 
 ### Changed
 - Add `cpp` extension to default `link_regex` of IPD crawler

CONFIG.md

@@ -223,6 +223,23 @@ is stored in the keyring.
 - `keyring_name`: The service name PFERD uses for storing credentials. (Default:
   `PFERD`)
 
+### The `pass` authenticator
+
+This authenticator queries the [`pass` password manager][3] for a username and
+password. It tries to be mostly compatible with [browserpass][4] and
+[passff][5], so see those links for an overview of the format. If PFERD fails
+to load your password, you can use the `--explain` flag to see why.
+
+- `passname`: The name of the password to use (Required)
+- `username_prefixes`: A comma-separated list of username line prefixes
+  (Default: `login,username,user`)
+- `password_prefixes`: A comma-separated list of password line prefixes
+  (Default: `password,pass,secret`)
+
+[3]: <https://www.passwordstore.org/> "Pass: The Standard Unix Password Manager"
+[4]: <https://github.com/browserpass/browserpass-extension#organizing-password-store> "Organizing password store"
+[5]: <https://github.com/passff/passff#multi-line-format> "Multi-line format"
+
 ### The `tfa` authenticator
 
 This authenticator prompts the user on the console for a two-factor
@@ -316,7 +333,7 @@ is a regular expression and `TARGET` an f-string based template. If a path
 matches `SOURCE`, the output path is created using `TARGET` as template.
 `SOURCE` is automatically anchored.
 
-`TARGET` uses Python's [format string syntax][3]. The *n*-th capturing group can
+`TARGET` uses Python's [format string syntax][6]. The *n*-th capturing group can
 be referred to as `{g<n>}` (e.g. `{g3}`). `{g0}` refers to the original path.
 If capturing group *n*'s contents are a valid integer, the integer value is
 available as `{i<n>}` (e.g. `{i3}`). If capturing group *n*'s contents are a
@@ -337,7 +354,7 @@ Example: `f(oo+)/be?ar -re-> B{g1.upper()}H/fear`
 - Converts `fooooo/bear` into `BOOOOOH/fear`
 - Converts `foo/bar/baz` into `BOOH/fear/baz`
 
-[3]: <https://docs.python.org/3/library/string.html#format-string-syntax> "Format String Syntax"
+[6]: <https://docs.python.org/3/library/string.html#format-string-syntax> "Format String Syntax"
 
 ### The `-name-re->` arrow
 

PFERD/auth/__init__.py

@@ -5,6 +5,7 @@ from ..config import Config
 from .authenticator import Authenticator, AuthError, AuthLoadError, AuthSection  # noqa: F401
 from .credential_file import CredentialFileAuthenticator, CredentialFileAuthSection
 from .keyring import KeyringAuthenticator, KeyringAuthSection
+from .pass_ import PassAuthenticator, PassAuthSection
 from .simple import SimpleAuthenticator, SimpleAuthSection
 from .tfa import TfaAuthenticator
 
@@ -19,6 +20,8 @@ AUTHENTICATORS: Dict[str, AuthConstructor] = {
         CredentialFileAuthenticator(n, CredentialFileAuthSection(s), c),
     "keyring": lambda n, s, c:
         KeyringAuthenticator(n, KeyringAuthSection(s)),
+    "pass": lambda n, s, c:
+        PassAuthenticator(n, PassAuthSection(s)),
     "simple": lambda n, s, c:
         SimpleAuthenticator(n, SimpleAuthSection(s)),
     "tfa": lambda n, s, c:

PFERD/auth/pass_.py

@@ -0,0 +1,98 @@
+import re
+import subprocess
+from typing import List, Tuple
+
+from ..logging import log
+from .authenticator import Authenticator, AuthError, AuthSection
+
+
+class PassAuthSection(AuthSection):
+    def passname(self) -> str:
+        if (value := self.s.get("passname")) is None:
+            self.missing_value("passname")
+        return value
+
+    def username_prefixes(self) -> List[str]:
+        value = self.s.get("username_prefixes", "login,username,user")
+        return [prefix.lower() for prefix in value.split(",")]
+
+    def password_prefixes(self) -> List[str]:
+        value = self.s.get("password_prefixes", "password,pass,secret")
+        return [prefix.lower() for prefix in value.split(",")]
+
+
+class PassAuthenticator(Authenticator):
+    PREFIXED_LINE_RE = r"([a-zA-Z]+):\s?(.*)"  # to be used with fullmatch
+
+    def __init__(self, name: str, section: PassAuthSection) -> None:
+        super().__init__(name)
+
+        self._passname = section.passname()
+        self._username_prefixes = section.username_prefixes()
+        self._password_prefixes = section.password_prefixes()
+
+    async def credentials(self) -> Tuple[str, str]:
+        log.explain_topic("Obtaining credentials from pass")
+
+        try:
+            log.explain(f"Calling 'pass show {self._passname}'")
+            result = subprocess.check_output(["pass", "show", self._passname], text=True)
+        except subprocess.CalledProcessError as e:
+            raise AuthError(f"Failed to get password info from {self._passname}: {e}")
+
+        prefixed = {}
+        unprefixed = []
+        for line in result.strip().splitlines():
+            if match := re.fullmatch(self.PREFIXED_LINE_RE, line):
+                prefix = match.group(1).lower()
+                value = match.group(2)
+                log.explain(f"Found prefixed line {line!r} with prefix {prefix!r}, value {value!r}")
+                if prefix in prefixed:
+                    raise AuthError(f"Prefix {prefix} specified multiple times")
+                prefixed[prefix] = value
+            else:
+                log.explain(f"Found unprefixed line {line!r}")
+                unprefixed.append(line)
+
+        username = None
+        for prefix in self._username_prefixes:
+            log.explain(f"Looking for username at prefix {prefix!r}")
+            if prefix in prefixed:
+                username = prefixed[prefix]
+                log.explain(f"Found username {username!r}")
+                break
+
+        password = None
+        for prefix in self._password_prefixes:
+            log.explain(f"Looking for password at prefix {prefix!r}")
+            if prefix in prefixed:
+                password = prefixed[prefix]
+                log.explain(f"Found password {password!r}")
+                break
+
+        if password is None and username is None:
+            log.explain("No username and password found so far")
+            log.explain("Using first unprefixed line as password")
+            log.explain("Using second unprefixed line as username")
+        elif password is None:
+            log.explain("No password found so far")
+            log.explain("Using first unprefixed line as password")
+        elif username is None:
+            log.explain("No username found so far")
+            log.explain("Using first unprefixed line as username")
+
+        if password is None:
+            if not unprefixed:
+                log.explain("Not enough unprefixed lines left")
+                raise AuthError("Password could not be determined")
+            password = unprefixed.pop(0)
+            log.explain(f"Found password {password!r}")
+
+        if username is None:
+            if not unprefixed:
+                log.explain("Not enough unprefixed lines left")
+                raise AuthError("Username could not be determined")
+            username = unprefixed.pop(0)
+            log.explain(f"Found username {username!r}")
+
+        return username, password