Merge pull request #9 from shadow-utils-rs/fix/1-7-critical-bugs

passwd: fix 7 critical bugs (#1-#7)

Cargo.toml

@@ -38,6 +38,9 @@ thiserror = "2"
 nix = { version = "0.29", features = ["user", "fs", "process", "signal", "term"] }
 libc = "0.2"
 
+# Security
+zeroize = "1"
+
 # Testing
 proptest = "1"
 tempfile = "3"

src/shadow-core/Cargo.toml

@@ -14,6 +14,7 @@ path = "src/lib.rs"
 libc = { workspace = true }
 nix = { workspace = true }
 thiserror = { workspace = true }
+zeroize = { workspace = true }
 
 [dev-dependencies]
 proptest = { workspace = true }

src/shadow-core/src/pam.rs

@@ -28,6 +28,8 @@ use std::io::{self, BufRead, Write};
 use std::os::unix::io::AsRawFd;
 use std::ptr;
 
+use zeroize::Zeroize;
+
 use crate::error::ShadowError;
 
 // ---------------------------------------------------------------------------
@@ -351,7 +353,13 @@ fn prompt_for_input(
     };
 
     match input {
-        Ok(line) => alloc_c_response(&line),
+        Ok(mut line) => {
+            let result = alloc_c_response(&line);
+            // Zeroize the Rust string so password data does not linger in
+            // process memory after being copied to the C-allocated response.
+            line.zeroize();
+            result
+        }
         Err(_) => Err(()),
     }
 }