feat: support downloading via token auth (#603)

src/auth.rs

@@ -2,11 +2,13 @@ use crate::{args::Args, server::Response, utils::unix_now};
 
 use anyhow::{anyhow, bail, Result};
 use base64::{engine::general_purpose::STANDARD, Engine as _};
+use ed25519_dalek::{ed25519::signature::SignerMut, Signature, SigningKey};
 use headers::HeaderValue;
 use hyper::{header::WWW_AUTHENTICATE, Method};
 use indexmap::IndexMap;
 use lazy_static::lazy_static;
 use md5::Context;
+use sha2::{Digest, Sha256};
 use std::{
     collections::HashMap,
     path::{Path, PathBuf},
@@ -14,7 +16,8 @@ use std::{
 use uuid::Uuid;
 
 const REALM: &str = "DUFS";
-const DIGEST_AUTH_TIMEOUT: u32 = 604800; // 7 days
+const DIGEST_AUTH_TIMEOUT: u32 = 60 * 60 * 24 * 7; // 7 days
+const TOKEN_EXPIRATION: u64 = 1000 * 60 * 60 * 24 * 3; // 3 days
 
 lazy_static! {
     static ref NONCESTARTHASH: Context = {
@@ -105,11 +108,21 @@ impl AccessControl {
         path: &str,
         method: &Method,
         authorization: Option<&HeaderValue>,
+        token: Option<&String>,
         guard_options: bool,
     ) -> (Option<String>, Option<AccessPaths>) {
         if self.users.is_empty() {
             return (None, Some(AccessPaths::new(AccessPerm::ReadWrite)));
         }
+
+        if method == Method::GET {
+            if let Some(token) = token {
+                if let Ok((user, ap)) = self.verifty_token(token, path) {
+                    return (Some(user), ap.guard(path, method));
+                }
+            }
+        }
+
         if let Some(authorization) = authorization {
             if let Some(user) = get_auth_user(authorization) {
                 if let Some((pass, ap)) = self.users.get(&user) {
@@ -135,6 +148,49 @@ impl AccessControl {
 
         (None, None)
     }
+
+    pub fn generate_token(&self, path: &str, user: &str) -> Result<String> {
+        let (pass, _) = self
+            .users
+            .get(user)
+            .ok_or_else(|| anyhow!("Not found user '{user}'"))?;
+        let exp = unix_now().as_millis() as u64 + TOKEN_EXPIRATION;
+        let message = format!("{path}:{exp}");
+        let mut signing_key = derive_secret_key(user, pass);
+        let sig = signing_key.sign(message.as_bytes()).to_bytes();
+
+        let mut raw = Vec::with_capacity(64 + 8 + user.len());
+        raw.extend_from_slice(&sig);
+        raw.extend_from_slice(&exp.to_be_bytes());
+        raw.extend_from_slice(user.as_bytes());
+
+        Ok(hex::encode(raw))
+    }
+
+    fn verifty_token<'a>(&'a self, token: &str, path: &str) -> Result<(String, &'a AccessPaths)> {
+        let raw = hex::decode(token)?;
+
+        let sig_bytes = &raw[..64];
+        let exp_bytes = &raw[64..72];
+        let user_bytes = &raw[72..];
+
+        let exp = u64::from_be_bytes(exp_bytes.try_into()?);
+        if unix_now().as_millis() as u64 > exp {
+            bail!("Token expired");
+        }
+
+        let user = std::str::from_utf8(user_bytes)?;
+        let (pass, ap) = self
+            .users
+            .get(user)
+            .ok_or_else(|| anyhow!("Not found user '{user}'"))?;
+
+        let sig = Signature::from_bytes(&<[u8; 64]>::try_from(sig_bytes)?);
+
+        let message = format!("{path}:{exp}");
+        derive_secret_key(user, pass).verify(message.as_bytes(), &sig)?;
+        Ok((user.to_string(), ap))
+    }
 }
 
 #[derive(Debug, Default, Clone, PartialEq, Eq)]
@@ -422,6 +478,13 @@ pub fn check_auth(
     }
 }
 
+fn derive_secret_key(user: &str, pass: &str) -> SigningKey {
+    let mut hasher = Sha256::new();
+    hasher.update(format!("{user}:{pass}").as_bytes());
+    let hash = hasher.finalize();
+    SigningKey::from_bytes(&hash.into())
+}
+
 /// Check if a nonce is still valid.
 /// Return an error if it was never valid
 fn validate_nonce(nonce: &[u8]) -> Result<bool> {
@@ -433,7 +496,7 @@ fn validate_nonce(nonce: &[u8]) -> Result<bool> {
         //get time
         if let Ok(secs_nonce) = u32::from_str_radix(&n[..8], 16) {
             //check time
-            let now = unix_now()?;
+            let now = unix_now();
             let secs_now = now.as_secs() as u32;
 
             if let Some(dur) = secs_now.checked_sub(secs_nonce) {
@@ -513,7 +576,7 @@ fn to_headermap(header: &[u8]) -> Result<HashMap<&[u8], &[u8]>, ()> {
 }
 
 fn create_nonce() -> Result<String> {
-    let now = unix_now()?;
+    let now = unix_now();
     let secs = now.as_secs() as u32;
     let mut h = NONCESTARTHASH.clone();
     h.consume(secs.to_be_bytes());