feat: use digest auth (#14)

* feat: switch to digest auth

* implement digest auth

* cargo fmt

* no lock

src/auth.rs

@@ -0,0 +1,209 @@
+use headers::HeaderValue;
+use lazy_static::lazy_static;
+use md5::Context;
+use std::{
+    collections::HashMap,
+    time::{SystemTime, UNIX_EPOCH},
+};
+use uuid::Uuid;
+
+use crate::BoxResult;
+
+const REALM: &str = "DUF";
+
+lazy_static! {
+    static ref NONCESTARTHASH: Context = {
+        let mut h = Context::new();
+        h.consume(Uuid::new_v4().as_bytes());
+        h.consume(std::process::id().to_be_bytes());
+        h
+    };
+}
+
+pub fn generate_www_auth(stale: bool) -> String {
+    let str_stale = if stale { "stale=true," } else { "" };
+    format!(
+        "Digest realm=\"{}\",nonce=\"{}\",{}qop=\"auth\",algorithm=\"MD5\"",
+        REALM,
+        create_nonce(),
+        str_stale
+    )
+}
+
+pub fn parse_auth(auth: &str) -> BoxResult<(String, String)> {
+    let p: Vec<&str> = auth.trim().split(':').collect();
+    let err = "Invalid auth value";
+    if p.len() != 2 {
+        return Err(err.into());
+    }
+    let user = p[0];
+    let pass = p[1];
+    let mut h = Context::new();
+    h.consume(format!("{}:{}:{}", user, REALM, pass).as_bytes());
+    Ok((user.to_owned(), format!("{:x}", h.compute())))
+}
+
+pub fn valid_digest(
+    header_value: &HeaderValue,
+    method: &str,
+    auth_user: &str,
+    auth_pass: &str,
+) -> Option<()> {
+    let digest_value = strip_prefix(header_value.as_bytes(), b"Digest ")?;
+    let user_vals = to_headermap(digest_value).ok()?;
+    if let (Some(username), Some(nonce), Some(user_response)) = (
+        user_vals
+            .get(b"username".as_ref())
+            .and_then(|b| std::str::from_utf8(*b).ok()),
+        user_vals.get(b"nonce".as_ref()),
+        user_vals.get(b"response".as_ref()),
+    ) {
+        match validate_nonce(nonce) {
+            Ok(true) => {}
+            _ => return None,
+        }
+        if auth_user != username {
+            return None;
+        }
+        let mut ha = Context::new();
+        ha.consume(method);
+        ha.consume(b":");
+        if let Some(uri) = user_vals.get(b"uri".as_ref()) {
+            ha.consume(uri);
+        }
+        let ha = format!("{:x}", ha.compute());
+        let mut correct_response = None;
+        if let Some(qop) = user_vals.get(b"qop".as_ref()) {
+            if qop == &b"auth".as_ref() || qop == &b"auth-int".as_ref() {
+                correct_response = Some({
+                    let mut c = Context::new();
+                    c.consume(&auth_pass);
+                    c.consume(b":");
+                    c.consume(nonce);
+                    c.consume(b":");
+                    if let Some(nc) = user_vals.get(b"nc".as_ref()) {
+                        c.consume(nc);
+                    }
+                    c.consume(b":");
+                    if let Some(cnonce) = user_vals.get(b"cnonce".as_ref()) {
+                        c.consume(cnonce);
+                    }
+                    c.consume(b":");
+                    c.consume(qop);
+                    c.consume(b":");
+                    c.consume(&*ha);
+                    format!("{:x}", c.compute())
+                });
+            }
+        }
+        let correct_response = match correct_response {
+            Some(r) => r,
+            None => {
+                let mut c = Context::new();
+                c.consume(&auth_pass);
+                c.consume(b":");
+                c.consume(nonce);
+                c.consume(b":");
+                c.consume(&*ha);
+                format!("{:x}", c.compute())
+            }
+        };
+        if correct_response.as_bytes() == *user_response {
+            // grant access
+            return Some(());
+        }
+    }
+    None
+}
+
+/// Check if a nonce is still valid.
+/// Return an error if it was never valid
+fn validate_nonce(nonce: &[u8]) -> Result<bool, ()> {
+    if nonce.len() != 34 {
+        return Err(());
+    }
+    //parse hex
+    if let Ok(n) = std::str::from_utf8(nonce) {
+        //get time
+        if let Ok(secs_nonce) = u32::from_str_radix(&n[..8], 16) {
+            //check time
+            let now = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
+            let secs_now = now.as_secs() as u32;
+
+            if let Some(dur) = secs_now.checked_sub(secs_nonce) {
+                //check hash
+                let mut h = NONCESTARTHASH.clone();
+                h.consume(secs_nonce.to_be_bytes());
+                let h = format!("{:x}", h.compute());
+                if h[..26] == n[8..34] {
+                    return Ok(dur < 300); // from the last 5min
+                                          //Authentication-Info ?
+                }
+            }
+        }
+    }
+    Err(())
+}
+
+fn strip_prefix<'a>(search: &'a [u8], prefix: &[u8]) -> Option<&'a [u8]> {
+    let l = prefix.len();
+    if search.len() < l {
+        return None;
+    }
+    if &search[..l] == prefix {
+        Some(&search[l..])
+    } else {
+        None
+    }
+}
+
+fn to_headermap(header: &[u8]) -> Result<HashMap<&[u8], &[u8]>, ()> {
+    let mut sep = Vec::new();
+    let mut asign = Vec::new();
+    let mut i: usize = 0;
+    let mut esc = false;
+    for c in header {
+        match (c, esc) {
+            (b'=', false) => asign.push(i),
+            (b',', false) => sep.push(i),
+            (b'"', false) => esc = true,
+            (b'"', true) => esc = false,
+            _ => {}
+        }
+        i += 1;
+    }
+    sep.push(i); // same len for both Vecs
+
+    i = 0;
+    let mut ret = HashMap::new();
+    for (&k, &a) in sep.iter().zip(asign.iter()) {
+        while header[i] == b' ' {
+            i += 1;
+        }
+        if a <= i || k <= 1 + a {
+            //keys and vals must contain one char
+            return Err(());
+        }
+        let key = &header[i..a];
+        let val = if header[1 + a] == b'"' && header[k - 1] == b'"' {
+            //escaped
+            &header[2 + a..k - 1]
+        } else {
+            //not escaped
+            &header[1 + a..k]
+        };
+        i = 1 + k;
+        ret.insert(key, val);
+    }
+    Ok(ret)
+}
+
+fn create_nonce() -> String {
+    let now = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
+    let secs = now.as_secs() as u32;
+    let mut h = NONCESTARTHASH.clone();
+    h.consume(secs.to_be_bytes());
+
+    let n = format!("{:08x}{:032x}", secs, h.compute());
+    n[..34].to_string()
+}