From 7365f0c5758954ea29b3e34648baca4b9876e624 Mon Sep 17 00:00:00 2001
From: Tomasz Kramkowski <tomasz@kramkow.ski>
Date: Sun, 29 Jan 2023 17:26:42 +0000
Subject: Remove dependency on pam-bindings

---
 Cargo.toml |  1 -
 src/lib.rs | 20 ++++++++++----------
 src/pam.rs | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 11 deletions(-)
 create mode 100644 src/pam.rs

diff --git a/Cargo.toml b/Cargo.toml
index 9b5594d..060453e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,4 +14,3 @@ crate-type = ["cdylib"]
 [dependencies]
 cap-std = "1.0.4"
 libc = "0.2.139"
-pam-bindings = "0.1.1"
diff --git a/src/lib.rs b/src/lib.rs
index c104a23..3fd0630 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,11 +1,12 @@
 // Copyright (C) 2023  Tomasz Kramkowski <tomasz@kramkow.ski>
 // SPDX-License-Identifier: MIT
 
+mod pam;
 mod passwd;
 
 use cap_std::fs::{Dir, OpenOptions};
-use pam::module::PamHandle;
-use std::ffi::{c_char, c_int, CString};
+use pam::PAMHandle;
+use std::ffi::{c_char, c_int, CStr};
 use std::io::{ErrorKind, Write};
 use std::panic;
 use std::path::Path;
@@ -31,9 +32,8 @@ impl From<std::io::Error> for SessionError {
     }
 }
 
-fn open_session(h: &PamHandle, mountpoint: &str) -> Result<(), SessionError> {
-    let user = h.get_user(None).or(Err(SessionError))?;
-    let user = CString::new(user).or(Err(SessionError))?;
+fn open_session(h: &PAMHandle, mountpoint: &str) -> Result<(), SessionError> {
+    let user = h.get_user::<CStr>(None).or(Err(SessionError))?;
     let uid = passwd::get_uid_by_name(&user).ok_or(SessionError)?;
     let uid = uid.to_string();
     let d = Dir::open_ambient_dir(mountpoint, cap_std::ambient_authority())?;
@@ -52,23 +52,23 @@ const CG_MOUNT: &str = "/sys/fs/cgroup";
 
 #[no_mangle]
 pub extern "C" fn pam_sm_open_session(
-    h: &mut PamHandle,
+    h: &mut PAMHandle,
     _flags: c_int,
     _argc: c_int,
     _argv: *const *const c_char,
 ) -> c_int {
     match panic::catch_unwind(|| open_session(h, CG_MOUNT)) {
-        Ok(Ok(())) => 0,
-        _ => 14,
+        Ok(Ok(())) => pam::SUCCESS,
+        _ => pam::SESSION_ERR,
     }
 }
 
 #[no_mangle]
 pub extern "C" fn pam_sm_close_session(
-    _h: &mut PamHandle,
+    _h: &mut PAMHandle,
     _flags: c_int,
     _argc: c_int,
     _argv: *const *const c_char,
 ) -> c_int {
-    0
+    pam::SUCCESS
 }
diff --git a/src/pam.rs b/src/pam.rs
new file mode 100644
index 0000000..17e4590
--- /dev/null
+++ b/src/pam.rs
@@ -0,0 +1,39 @@
+use core::marker::{PhantomData, PhantomPinned};
+use std::ffi::{c_char, c_int, CStr, CString};
+
+#[repr(C)]
+pub struct PAMHandle {
+    _data: [u8; 0],
+    _marker: PhantomData<(*mut u8, PhantomPinned)>,
+}
+
+pub const SUCCESS: c_int = 0;
+pub const SESSION_ERR: c_int = 14;
+
+extern "C" {
+    fn pam_get_user(
+        pamh: *const PAMHandle,
+        user: &*const c_char,
+        prompt: *const c_char,
+    ) -> c_int;
+}
+
+impl PAMHandle {
+    pub fn get_user<S: AsRef<CStr> + ?Sized>(
+        &self,
+        prompt: Option<&S>,
+    ) -> Result<CString, c_int> {
+        let ptr: *const c_char = std::ptr::null_mut();
+        let prompt = match prompt {
+            Some(prompt) => prompt.as_ref().as_ptr(),
+            None => core::ptr::null(),
+        };
+        match unsafe { pam_get_user(self, &ptr, prompt) } {
+            SUCCESS if !ptr.is_null() => {
+                let cstr = unsafe { CStr::from_ptr(ptr) };
+                Ok(CString::from(cstr))
+            }
+            e => Err(e),
+        }
+    }
+}
-- 
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