decode securityIdentifier attribute as SID

README.md

@@ -18,6 +18,34 @@ CLI tool to query LDAP/AD servers
   * By default the first 1000 entries are shown, and it errors if there are more results
   * Use `--all` to show all results
 
+## Virtual attributes
+
+`ldaptool` supports constructing new values from existing attributes by adding a `:<postprocess>` suffix (which can be chained apart from the length limit).
+
+* Some suffixes support an argument as `:<postprocess>[<arg>]`.
+* A single integer as postprocess suffix limits the length of the value; it replaces the last character of the output with `…` if it cut something off.
+* Multi-valued attributes generate multiple virtual attrites; each value is processed individually. (The values are joined afterwards for table output if needed.)
+
+### DN handling
+
+DNs are decoded into lists of lists of `(name, value)` pairs (the inner list usually contains exactly one entry).
+Attributes with a `DC` name are considered part of the "domain", everything else belongs to the "path".
+(Usually a DN will start with path segments and end with domain segments.)
+The path is read from back to front.
+
+The following postprocess hooks are available:
+* `domain`: extracts the domain as DNS FQDN (`CN=Someone,OU=Dep1,DC=example,DC=com` becomes `example.com`)
+* `path`: extracts the non-domain parts without names and separates them by `/` (`CN=Someone,OU=Dep1,DC=example,DC=com` becomes `Dep1/Someone`)
+* `fullpath`: uses the `domain` as first segment in a path (`CN=Someone,OU=Dep1,DC=example,DC=com` becomes `example.com/Dep1/Someone`)
+* `dnslice`: extracts a "slice" from a DN (outer list only); the result is still in DN format.
+
+`path`, `fullpath` and `dnslice` take an optional index/slice as argument, written in python syntax.
+For `path` and `fullpath` this extracts only the given index/slice from the path (`fullpath` always includes the full FQDN as first segment), `dnslice` operates on the outer list of decoded (lists of) pairs:
+
+* `dn:dnslice[1:]` on `dn: CN=Someone,OU=Dep1,DC=example,DC=com` returns `OU=Dep1,DC=example,DC=com`
+* `dn:fullpath[:-1]` on `dn: CN=Someone,OU=Dep1,DC=example,DC=com` returns `example.com/Dep1`
+* `dn:path[-1]` on `dn: CN=Someone,OU=Dep1,DC=example,DC=com` returns `Someone`
+
 ## Authentication, Protocol, Ports
 
 `ldaptool` always uses TLS for password based authentication, and SASL GSS-API over non-TLS for Kerberos ones.

src/ldaptool/_utils/dninfo.py

@@ -33,19 +33,26 @@ class DNInfo:
     def domain(self) -> str:
         return ".".join(ava[1] for rdn in self.parts for ava in rdn if ava[0].lower() == "dc")
 
-    def _path(self, *, escape: typing.Callable[[str], str], sep: str) -> str:
+    def _path(self, *, escape: typing.Callable[[str], str], sep: str, selection: slice = slice(None)) -> str:
-        return sep.join(escape(ava[1]) for rdn in reversed(self.parts) for ava in rdn if ava[0].lower() != "dc")
+        rev_flattened = [ava[1] for rdn in reversed(self.parts) for ava in rdn if ava[0].lower() != "dc"]
+        return sep.join(value for value in rev_flattened[selection])
+
+    def sliced_path(self, selection: slice, /) -> str:
+        return self._path(escape=lambda value: _escape_backslash(value, special="/"), sep="/", selection=selection)
 
     @functools.cached_property
     def path(self) -> str:
-        return self._path(escape=lambda value: _escape_backslash(value, special="/"), sep="/")
+        return self.sliced_path(slice(None))
 
-    @property
+    def sliced_full_path(self, selection: slice, /) -> str:
-    def full_path(self) -> str:
         domain = self.domain
-        path = self.path
+        path = self.sliced_path(selection)
         if not path:
             return self.domain
         if not domain:
             return self.path
         return f"{domain}/{path}"
+
+    @property
+    def full_path(self) -> str:
+        return self.sliced_full_path(slice(None))

src/ldaptool/decode/_decoder.py

@@ -101,7 +101,7 @@ class Attribute:
                 return
 
     def _try_decode(self, args: Arguments) -> None:
-        if self.name in ("objectSid",):
+        if self.name in ("objectSid","securityIdentifier"):
             self._try_decode_sid()
         elif self.name in ("msExchMailboxGuid", "objectGUID"):
             self._try_decode_uuid()

src/ldaptool/decode/_postprocess.py

@@ -2,6 +2,9 @@ from __future__ import annotations
 
 import abc
 import dataclasses
+import typing
+
+import ldap.dn
 
 from ldaptool._utils.dninfo import DNInfo
 
@@ -14,6 +17,27 @@ class Step(abc.ABC):
         ...
 
 
+def _args_to_slice(args: str) -> slice:
+    args = args.strip()
+    if not args:
+        return slice(None)
+    params: list[typing.Optional[int]] = []
+    for arg in args.split(":"):
+        arg = arg.strip()
+        if arg:
+            params.append(int(arg))
+        else:
+            params.append(None)
+    if len(params) == 1:
+        assert isinstance(params[0], int)
+        ndx = params[0]
+        if ndx == -1:
+            return slice(ndx, None)  # from last element to end - still exactly one element
+        # this doesn't work for ndx == -1: slice(-1, 0) is always empty. otherwise it should return [ndx:][:1].
+        return slice(ndx, ndx + 1)
+    return slice(*params)
+
+
 @dataclasses.dataclass(slots=True)
 class MaxLength(Step):
     limit: int
@@ -26,6 +50,10 @@ class MaxLength(Step):
 
 @dataclasses.dataclass(slots=True)
 class DNDomain(Step):
+    def __init__(self, args: str) -> None:
+        if args:
+            raise ValueError(":domain doesn't support an argument")
+
     def step(self, value: str) -> str:
         try:
             dninfo = DNInfo(dn=value)
@@ -37,30 +65,57 @@ class DNDomain(Step):
 
 @dataclasses.dataclass(slots=True)
 class DNPath(Step):
+    path_slice: slice
+
+    def __init__(self, args: str) -> None:
+        self.path_slice = _args_to_slice(args)
+
     def step(self, value: str) -> str:
         try:
             dninfo = DNInfo(dn=value)
         except Exception:
             # not a valid DN -> no processing
             return value
-        return dninfo.path
+        return dninfo.sliced_path(self.path_slice)
 
 
 @dataclasses.dataclass(slots=True)
 class DNFullPath(Step):
+    path_slice: slice
+
+    def __init__(self, args: str) -> None:
+        self.path_slice = _args_to_slice(args)
+
     def step(self, value: str) -> str:
         try:
             dninfo = DNInfo(dn=value)
         except Exception:
             # not a valid DN -> no processing
             return value
-        return dninfo.full_path
+        return dninfo.sliced_full_path(self.path_slice)
 
 
-_STEPS = {
+@dataclasses.dataclass(slots=True)
-    "domain": DNDomain(),
+class DNSlice(Step):
-    "path": DNPath(),
+    slice: slice
-    "fullpath": DNFullPath(),
+
+    def __init__(self, args: str) -> None:
+        self.slice = _args_to_slice(args)
+
+    def step(self, value: str) -> str:
+        try:
+            dninfo = DNInfo(dn=value)
+        except Exception:
+            # not a valid DN -> no processing
+            return value
+        return ldap.dn.dn2str(dninfo.parts[self.slice])  # type: ignore
+
+
+_STEPS: dict[str, typing.Callable[[str], Step]] = {
+    "domain": DNDomain,
+    "path": DNPath,
+    "fullpath": DNFullPath,
+    "dnslice": DNSlice,
 }
 
 
@@ -78,19 +133,63 @@ class PostProcess:
         return value
 
 
-def parse_steps(steps: list[str]) -> PostProcess:
+def parse_steps(steps: str) -> PostProcess:
-    max_len = 0
+    result: list[Step] = []
-    try:
+
-        max_len = int(steps[-1])
+    cur_id_start = 0
-        steps.pop()
+    cur_args_start = -1
-    except ValueError:
+    current_id = ""
-        pass
+    current_args = ""
-    result = []
+    count_brackets = 0
-    for step in steps:
+    step_done = False
-        step_i = _STEPS.get(step, None)
+
+    def handle_step() -> None:
+        nonlocal cur_id_start, cur_args_start, current_id, current_args, step_done
+        assert step_done
+
+        step_i = _STEPS.get(current_id, None)
         if step_i is None:
-            raise InvalidStep(f"Unknown post-processing step {step!r}")
+            try:
-        result.append(step_i)
+                max_len = int(current_id)
-    if max_len:
+                result.append(MaxLength(max_len))
-        result.append(MaxLength(max_len))
+            except ValueError:
+                raise InvalidStep(f"Unknown post-processing step {current_id!r}")
+        else:
+            result.append(step_i(current_args))
+
+        cur_id_start = pos + 1
+        cur_args_start = -1
+        current_id = ""
+        current_args = ""
+        step_done = False
+
+    for pos, char in enumerate(steps):
+        if step_done:
+            if char != ":":
+                raise InvalidStep(f"Require : after step, found {char!r} at pos {pos}")
+            handle_step()
+        elif char == "[":
+            if count_brackets == 0:
+                # end of identifier
+                current_id = steps[cur_id_start:pos]
+                cur_args_start = pos + 1
+            count_brackets += 1
+        elif char == "]":
+            count_brackets -= 1
+            if count_brackets == 0:
+                current_args = steps[cur_args_start:pos]
+                step_done = True
+        elif count_brackets:
+            continue
+        elif not char.isalnum():
+            raise InvalidStep(f"Expecting either alphanumeric, ':' or '[', got {char!r} at {pos}")
+
+    if not step_done:
+        current_id = steps[cur_id_start:]
+        if current_id:
+            step_done = True
+
+    if step_done:
+        handle_step()
+
     return PostProcess(result)

src/ldaptool/decode/arguments.py

@@ -57,20 +57,20 @@ class Arguments(argclasses.BaseArguments):
             self.columns_keys.append(column)
 
             if column == "dndomain":
-                self.post_process.setdefault("dn", {})[column] = _postprocess.parse_steps(["domain"])
+                self.post_process.setdefault("dn", {})[column] = _postprocess.parse_steps("domain")
                 attributes_set.add("dn")
             elif column == "dnpath":
-                self.post_process.setdefault("dn", {})[column] = _postprocess.parse_steps(["path"])
+                self.post_process.setdefault("dn", {})[column] = _postprocess.parse_steps("path")
                 attributes_set.add("dn")
             elif column == "dnfullpath":
-                self.post_process.setdefault("dn", {})[column] = _postprocess.parse_steps(["fullpath"])
+                self.post_process.setdefault("dn", {})[column] = _postprocess.parse_steps("fullpath")
                 attributes_set.add("dn")
             else:
-                step_names = column.split(":")
+                col_parts = column.split(":", maxsplit=1)
-                attributes_set.add(step_names[0])
+                attributes_set.add(col_parts[0])
-                if len(step_names) > 1:
+                if len(col_parts) == 2:
-                    source = step_names.pop(0)
+                    source, steps = col_parts
-                    self.post_process.setdefault(source, {})[column] = _postprocess.parse_steps(step_names)
+                    self.post_process.setdefault(source, {})[column] = _postprocess.parse_steps(steps)
 
         if all_attributes:
             self.attributes = []