python bindings: add a minimal README

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] ##
 ### Fixes ###
+- python bindings: add a minimal README for PyPI.
+
 - python bindings: actually export `PROC_ROOT`.
 
 ## [0.1.1] - 2024-10-01 ##

contrib/bindings/python/README.md

@@ -0,0 +1,85 @@
+## python-pathrs ##
+
+This is a basic Python wrapper around [libpathrs][libpathrs], a safe path
+resolution library for Linux. For more details about the security protections
+provided by [libpathrs][libpathrs], [see the main README][libpathrs-readme].
+
+In order to use this library, you need to have `libpathrs.so` installed on your
+system.
+
+### Examples ###
+
+libpathrs allows you to operate on a container root filesystem safely, without
+worrying about an attacker swapping components and tricking you into operating
+on host files.
+
+```python
+import pathrs
+
+# Get a handle to the root filesystem.
+with pathrs.Root("/path/to/rootfs") as root:
+    # Get an O_PATH handle to a path we want to operate on.
+    with root.resolve("/etc/passwd") as passwd:
+        # Upgrade the handle to one you can do regular IO on.
+        with root.reopen("r") as f:
+            for line in f:
+                print(line.rstrip("\n"))
+```
+
+Aside from just opening files, libpathrs also allows you to do most common
+filesystem operations:
+
+```python
+import pathrs
+
+# <fcntl.h>
+RENAME_EXCHANGE = 0x2
+
+with pathrs.Root("/path/to/rootfs") as root:
+    # symlink
+    root.symlink("foo", "bar") # foo -> bar
+    # link
+    root.hardlink("a", "b") # a -> b
+    # rename(at2)
+    root.rename("foo", "b", flags=RENAME_EXCHANGE) # foo <-> b
+    # open(O_CREAT)
+    with root.creat("newfile", "w+") as f:
+        f.write("Some contents.")
+```
+
+It also supports operations like `mkdir -p` and `rm -f`, which are a little
+tricky to implement safely.
+
+```python
+import pathrs
+
+with pathrs.Root("/path/to/rootfs") as root:
+    # rm -r
+    root.remove_all("/tmp/foo")
+    # mkdir -p
+    root.mkdir_all("/tmp/foo/bar/baz/bing/boop", 0o755)
+```
+
+In addition, libpathrs provides a safe `procfs` API, to allow for privileged
+programs to operate on `/proc` in a way that detects a maliciously-configured
+mount table. This is a somewhat esoteric requirement, but privileged processes
+that have to operate in untrusted mount namespaces need to handle this
+properly or risk serious security issues.
+
+```python
+import pathrs
+
+# readlink("/proc/thread-self/fd/0")
+stdin_path = pathrs.proc_readlink(pathrs.PROC_THREAD_SELF, "fd/0")
+
+# readlink("/proc/self/exe")
+exe_path = pathrs.proc_readlink(pathrs.PROC_SELF, "exe")
+
+# Read data from /proc/cpuinfo.
+with pathrs.proc_open(pathrs.PROC_ROOT, "cpuinfo", "r") as cpuinfo:
+    for line in cpuinfo:
+        print(line.rstrip("\n"))
+```
+
+[libpathrs]: /~https://github.com/openSUSE/libpathrs
+[libpathrs-readme]: /~https://github.com/openSUSE/libpathrs/blob/main/README.md

contrib/bindings/python/pyproject.toml

@@ -29,6 +29,7 @@ name = "pathrs"
 # TODO: Figure out a way to keep this version up-to-date with Cargo.toml.
 version = "0.1.1+dev"
 description = "Python bindings for libpathrs, a safe path resolution library for Linux."
+readme = "README.md"
 keywords = ["libpathrs", "pathrs"]
 license = { file = "COPYING.APACHE-2.0" }
 authors = [
@@ -57,3 +58,4 @@ dependencies = [
 [project.urls]
 Homepage = "/~https://github.com/openSUSE/libpathrs"
 Repository = "/~https://github.com/openSUSE/libpathrs"
+Documentation = "https://docs.rs/pathrs"