From 6b89e0dcb0d3a513d548fb38c08d4b66a353f364 Mon Sep 17 00:00:00 2001
From: Tomasz Kramkowski <tomasz@kramkow.ski>
Date: Mon, 30 Jan 2023 13:33:22 +0000
Subject: Basic pam_syslog error reporting

---
 src/lib.rs    | 34 ++++++++++++++++++++++++++++++----
 src/pam.rs    |  7 +++++++
 src/syslog.rs | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 85 insertions(+), 4 deletions(-)
 create mode 100644 src/syslog.rs

diff --git a/src/lib.rs b/src/lib.rs
index 3ffbb69..42a9c1b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,14 +3,16 @@
 
 mod pam;
 mod passwd;
+mod syslog;
 
 use cap_std::fs::{Dir, OpenOptions};
 use pam::PAMHandle;
-use std::ffi::{c_char, c_int, CStr};
+use std::ffi::{c_char, c_int, CStr, CString};
 use std::io::{ErrorKind, Write};
 use std::panic;
 use std::path::Path;
 use std::process;
+use syslog::{Facility, Level, Priority};
 
 fn create_and_open_dir<P: AsRef<Path> + ?Sized>(
     d: &Dir,
@@ -32,10 +34,34 @@ impl From<std::io::Error> for SessionError {
     }
 }
 
+const PRIORITY: Priority = Priority {
+    level: Level::Debug,
+    facility: Facility::Auth,
+};
+
 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 user = match h.get_user::<CStr>(None) {
+        Ok(user) => user,
+        Err(e) => {
+            if let Ok(message) =
+                CString::new(format!("Failure to get username: {e}"))
+            {
+                h.syslog(PRIORITY, &message);
+            }
+            return Err(SessionError);
+        }
+    };
+    let uid = match passwd::get_uid_by_name(&user) {
+        Some(uid) => uid.to_string(),
+        None => {
+            if let Ok(message) =
+                CString::new(format!("Failure to map user {user:?} to passwd entry"))
+            {
+                h.syslog(PRIORITY, &message);
+            }
+            return Err(SessionError);
+        }
+    };
     let d = Dir::open_ambient_dir(mountpoint, cap_std::ambient_authority())?;
     let d = create_and_open_dir(&d, "user")?;
     let d = create_and_open_dir(&d, &uid)?;
diff --git a/src/pam.rs b/src/pam.rs
index 81d543e..7905a92 100644
--- a/src/pam.rs
+++ b/src/pam.rs
@@ -1,3 +1,4 @@
+use crate::syslog::Priority;
 use core::marker::{PhantomData, PhantomPinned};
 use std::ffi::{c_char, c_int, CStr, CString};
 
@@ -17,6 +18,7 @@ extern "C" {
         user: &*const c_char,
         prompt: *const c_char,
     ) -> c_int;
+    fn pam_syslog(pamh: *const PAMHandle, priority: c_int, fmt: *const c_char, ...);
 }
 
 impl PAMHandle {
@@ -37,4 +39,9 @@ impl PAMHandle {
             e => Err(e),
         }
     }
+    pub fn syslog<S: AsRef<CStr> + ?Sized>(&self, priority: Priority, entry: &S) {
+        let Ok(fmt) = CString::new("%s") else { return };
+        let entry = entry.as_ref();
+        unsafe { pam_syslog(self, priority.into(), fmt.as_ptr(), entry.as_ptr()) }
+    }
 }
diff --git a/src/syslog.rs b/src/syslog.rs
new file mode 100644
index 0000000..65c8283
--- /dev/null
+++ b/src/syslog.rs
@@ -0,0 +1,48 @@
+use std::ffi::c_int;
+
+#[rustfmt::skip]
+pub enum Level {
+    Emergency = 0,
+    Alert     = 1,
+    Critical  = 2,
+    Error     = 3,
+    Warning   = 4,
+    Notice    = 5,
+    Info      = 6,
+    Debug     = 7,
+}
+
+#[rustfmt::skip]
+pub enum Facility {
+    Kernel   =  0 << 3,
+    User     =  1 << 3,
+    Mail     =  2 << 3,
+    Daemon   =  3 << 3,
+    Auth     =  4 << 3,
+    Syslog   =  5 << 3,
+    Lpr      =  6 << 3,
+    News     =  7 << 3,
+    Uucp     =  8 << 3,
+    Cron     =  9 << 3,
+    AuthPriv = 10 << 3,
+    Ftp      = 11 << 3,
+    Local0   = 12 << 3,
+    Local1   = 13 << 3,
+    Local2   = 14 << 3,
+    Local3   = 15 << 3,
+    Local4   = 16 << 3,
+    Local5   = 17 << 3,
+    Local6   = 18 << 3,
+    Local7   = 19 << 3,
+}
+
+pub struct Priority {
+    pub level: Level,
+    pub facility: Facility,
+}
+
+impl Into<c_int> for Priority {
+    fn into(self) -> c_int {
+        self.level as c_int | self.facility as c_int
+    }
+}
-- 
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