the log wrapper in C/C++ accepts formats

rust-backend/src/lib.rs

@@ -7,6 +7,7 @@
 use std::ffi::CStr;
 use std::os::raw::c_char;
 use std::panic::{catch_unwind, AssertUnwindSafe};
+use std::env;
 
 mod auth;
 mod logging;
@@ -15,14 +16,19 @@ mod error;
 #[no_mangle]
 pub extern "C" fn rust_init_logging(log_path: *const c_char) {
     let _ = catch_unwind(AssertUnwindSafe(|| {
-        let path = unsafe {
-            if log_path.is_null() {
-                "/var/log/pam_rust_backend.log"
-            } else {
-                CStr::from_ptr(log_path).to_str().unwrap_or("/var/log/pam_rust_backend.log")
+        let env_path = env::var("PAM_RUST_LOG_PATH").ok().and_then(|s| if s.is_empty() { None } else { Some(s) });
+        let path = if let Some(p) = env_path {
+            p
+        } else {
+            unsafe {
+                if log_path.is_null() {
+                    "/var/log/pam_rust_backend.log".to_string()
+                } else {
+                    CStr::from_ptr(log_path).to_str().unwrap_or("/var/log/pam_rust_backend.log").to_string()
+                }
             }
         };
-        logging::init_logger(path);
+        logging::init_logger(&path);
     }));
 }