From 653c5d682fb23a57cb39255da0164636ddefb7ab Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom.smeding@gmail.com>
Date: Thu, 17 Sep 2020 23:57:46 +0200
Subject: rust: Proper authentication data generation

---
 rust/src/auth.rs | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 rust/src/auth.rs

(limited to 'rust/src/auth.rs')

diff --git a/rust/src/auth.rs b/rust/src/auth.rs
new file mode 100644
index 0000000..51b4820
--- /dev/null
+++ b/rust/src/auth.rs
@@ -0,0 +1,84 @@
+// use users::get_current_username;
+// use dirs::data_dir;
+use std::borrow::Borrow;
+use std::ops::Deref;
+use std::{fs, io};
+use std::path::{Path, PathBuf};
+use rand::{Rng, CryptoRng};
+use crate::error::{IntoIOError, IntoIOResult};
+
+pub struct User(String);
+pub struct Pass(String);
+
+impl Borrow<str> for User { fn borrow(&self) -> &str { &self.0 } }
+impl Borrow<str> for Pass { fn borrow(&self) -> &str { &self.0 } }
+
+impl Deref for User { type Target = str; fn deref(&self) -> &Self::Target { &self.0 } }
+impl Deref for Pass { type Target = str; fn deref(&self) -> &Self::Target { &self.0 } }
+
+static PASSWORD_FILE_SUBDIR: &str = "tomsg_client";  // ~/.local/share/PASSWORD_FILE_SUBDIR/...
+static PASSWORD_FILE_SUBDIR_HOME: &str = ".tomsg_client";  // ~/PASSWORD_FILE_SUBDIR_HOME/...
+static PASSWORD_FILE_NAME: &str = "password.txt";
+
+pub fn get_auth_info() -> io::Result<(User, Pass)> {
+    Ok((get_username()?, obtain_password()?))
+}
+
+fn get_username() -> io::Result<User> {
+    match users::get_current_username().map(|u| u.to_str().map(|u| u.to_string())) {
+        Some(Some(u)) => Ok(User(u)),
+        Some(None) => Err("Username not valid UTF-8".ioerr()),
+        None => Err("Cannot obtain username".ioerr()),
+    }
+}
+
+fn obtain_password() -> io::Result<Pass> {
+    let dir = storage_directory()?;
+    if let Ok(pass) = read_password(&dir) {
+        return Ok(pass);
+    }
+
+    let pass = generate_password();
+    write_password(&dir, &pass)
+        .map_err(|e| format!("Cannot write password to home directory: {}", e).ioerr())?;
+    Ok(pass)
+}
+
+fn read_password(data_dir: &Path) -> io::Result<Pass> {
+    fs::read(data_dir.join(PASSWORD_FILE_NAME))
+        .and_then(|mut v| {
+            // Trim final newline if there is one
+            if v.last() == Some(&b'\n') {
+                v.pop();
+            }
+            String::from_utf8(v).map(Pass).iores()
+        })
+}
+
+fn write_password(data_dir: &Path, pass: &Pass) -> io::Result<()> {
+    fs::create_dir_all(data_dir)?;
+    fs::write(data_dir.join(PASSWORD_FILE_NAME), pass.as_bytes())
+}
+
+fn storage_directory() -> io::Result<PathBuf> {
+    dirs::data_dir()
+        .map(|mut dir| { dir.push(PASSWORD_FILE_SUBDIR); dir })
+        .or_else(|| dirs::home_dir()
+                        .map(|mut dir| {
+                            dir.push(PASSWORD_FILE_SUBDIR_HOME); dir
+                        }))
+        .ok_or("Cannot determine home directory".ioerr())
+}
+
+fn generate_password() -> Pass {
+    Pass(secure_rng()
+            .sample_iter(rand::distributions::Alphanumeric)
+            .take(32)
+            .collect::<String>()
+    )
+}
+
+// Wrapper for thread_rng() that statically enforces that the generator is CryptoRng.
+fn secure_rng() -> impl Rng + CryptoRng {
+    rand::thread_rng()
+}
-- 
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