Fix quality parse error in Accept-Encoding HTTP header (#2344)

CHANGES.md

@@ -4,10 +4,15 @@
 ### Added
 * Re-export actix-service `ServiceFactory` in `dev` module. [#2325]
 
-### Changes
+### Changed
 * Minimum supported Rust version (MSRV) is now 1.51.
+* Compress middleware will return 406 Not Acceptable when no content encoding is acceptable to the client. [#2344]
+
+### Fixed
+* Fix quality parse error in Accept-Encoding header. [#2344]
 
 [#2325]: https://github.com/actix/actix-web/pull/2325
+[#2344]: https://github.com/actix/actix-web/pull/2344
 
 
 ## 4.0.0-beta.8 - 2021-06-26

actix-http/CHANGES.md

@@ -1,22 +1,23 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
-### Changes
+### Changed
 * Minimum supported Rust version (MSRV) is now 1.51.
 
 ### Fixed
 * Remove slice creation pointing to potential uninitialized data on h1 encoder. [#2364]
 * Remove `Into<Error>` bound on `Encoder` body types. [#2375]
+* Fix quality parse error in Accept-Encoding header. [#2344]
 
 [#2364]: https://github.com/actix/actix-web/pull/2364
 [#2375]: https://github.com/actix/actix-web/pull/2375
+[#2344]: https://github.com/actix/actix-web/pull/2344
 
 
 ## 3.0.0-beta.8 - 2021-08-09
 ### Fixed
 * Potential HTTP request smuggling vulnerabilities. [RUSTSEC-2021-0081](https://github.com/rustsec/advisory-db/pull/977)
 
-
 ## 3.0.0-beta.8 - 2021-06-26
 ### Changed
 * Change compression algorithm features flags. [#2250]

actix-http/src/encoding/decoder.rs

@@ -1,6 +1,7 @@
 //! Stream decoders.
 
 use std::{
+    convert::TryFrom,
     future::Future,
     io::{self, Write as _},
     pin::Pin,
@@ -80,7 +81,7 @@ where
         let encoding = headers
             .get(&CONTENT_ENCODING)
             .and_then(|val| val.to_str().ok())
-            .map(ContentEncoding::from)
+            .and_then(|x| ContentEncoding::try_from(x).ok())
             .unwrap_or(ContentEncoding::Identity);
 
         Self::new(stream, encoding)

actix-http/src/header/shared/content_encoding.rs

@@ -1,4 +1,4 @@
-use std::{convert::Infallible, str::FromStr};
+use std::{convert::TryFrom, error, fmt, str::FromStr};
 
 use http::header::InvalidHeaderValue;
 
@@ -8,6 +8,20 @@ use crate::{
     HttpMessage,
 };
 
+/// Error return when a content encoding is unknown.
+///
+/// Example: 'compress'
+#[derive(Debug)]
+pub struct ContentEncodingParseError;
+
+impl fmt::Display for ContentEncodingParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Unsupported content encoding")
+    }
+}
+
+impl error::Error for ContentEncodingParseError {}
+
 /// Represents a supported content encoding.
 #[derive(Copy, Clone, PartialEq, Debug)]
 pub enum ContentEncoding {
@@ -37,7 +51,7 @@ impl ContentEncoding {
         matches!(self, ContentEncoding::Identity | ContentEncoding::Auto)
     }
 
-    /// Convert content encoding to string
+    /// Convert content encoding to string.
     #[inline]
     pub fn as_str(self) -> &'static str {
         match self {
@@ -48,18 +62,6 @@ impl ContentEncoding {
             ContentEncoding::Identity | ContentEncoding::Auto => "identity",
         }
     }
-
-    /// Default Q-factor (quality) value.
-    #[inline]
-    pub fn quality(self) -> f64 {
-        match self {
-            ContentEncoding::Br => 1.1,
-            ContentEncoding::Gzip => 1.0,
-            ContentEncoding::Deflate => 0.9,
-            ContentEncoding::Identity | ContentEncoding::Auto => 0.1,
-            ContentEncoding::Zstd => 0.0,
-        }
-    }
 }
 
 impl Default for ContentEncoding {
@@ -69,31 +71,33 @@ impl Default for ContentEncoding {
 }
 
 impl FromStr for ContentEncoding {
-    type Err = Infallible;
+    type Err = ContentEncodingParseError;
 
     fn from_str(val: &str) -> Result<Self, Self::Err> {
-        Ok(Self::from(val))
-    }
-}
-
-impl From<&str> for ContentEncoding {
-    fn from(val: &str) -> ContentEncoding {
         let val = val.trim();
 
         if val.eq_ignore_ascii_case("br") {
-            ContentEncoding::Br
+            Ok(ContentEncoding::Br)
         } else if val.eq_ignore_ascii_case("gzip") {
-            ContentEncoding::Gzip
+            Ok(ContentEncoding::Gzip)
         } else if val.eq_ignore_ascii_case("deflate") {
-            ContentEncoding::Deflate
+            Ok(ContentEncoding::Deflate)
         } else if val.eq_ignore_ascii_case("zstd") {
-            ContentEncoding::Zstd
+            Ok(ContentEncoding::Zstd)
         } else {
-            ContentEncoding::default()
+            Err(ContentEncodingParseError)
         }
     }
 }
 
+impl TryFrom<&str> for ContentEncoding {
+    type Error = ContentEncodingParseError;
+
+    fn try_from(val: &str) -> Result<Self, Self::Error> {
+        val.parse()
+    }
+}
+
 impl IntoHeaderValue for ContentEncoding {
     type Error = InvalidHeaderValue;
 

actix-http/src/header/shared/quality_item.rs

@@ -1,11 +1,14 @@
 use std::{
     cmp,
     convert::{TryFrom, TryInto},
-    fmt, str,
+    fmt,
+    str::{self, FromStr},
 };
 
 use derive_more::{Display, Error};
 
+use crate::error::ParseError;
+
 const MAX_QUALITY: u16 = 1000;
 const MAX_FLOAT_QUALITY: f32 = 1.0;
 
@@ -113,12 +116,12 @@ impl<T: fmt::Display> fmt::Display for QualityItem<T> {
     }
 }
 
-impl<T: str::FromStr> str::FromStr for QualityItem<T> {
+impl<T: FromStr> FromStr for QualityItem<T> {
-    type Err = crate::error::ParseError;
+    type Err = ParseError;
 
-    fn from_str(qitem_str: &str) -> Result<QualityItem<T>, crate::error::ParseError> {
+    fn from_str(qitem_str: &str) -> Result<Self, Self::Err> {
         if !qitem_str.is_ascii() {
-            return Err(crate::error::ParseError::Header);
+            return Err(ParseError::Header);
         }
 
         // Set defaults used if parsing fails.
@@ -139,7 +142,7 @@ impl<T: str::FromStr> str::FromStr for QualityItem<T> {
             if parts[0].len() < 2 {
                 // Can't possibly be an attribute since an attribute needs at least a name followed
                 // by an equals sign. And bare identifiers are forbidden.
-                return Err(crate::error::ParseError::Header);
+                return Err(ParseError::Header);
             }
 
             let start = &parts[0][0..2];
@@ -148,25 +151,21 @@ impl<T: str::FromStr> str::FromStr for QualityItem<T> {
                 let q_val = &parts[0][2..];
                 if q_val.len() > 5 {
                     // longer than 5 indicates an over-precise q-factor
-                    return Err(crate::error::ParseError::Header);
+                    return Err(ParseError::Header);
                 }
 
-                let q_value = q_val
+                let q_value = q_val.parse::<f32>().map_err(|_| ParseError::Header)?;
-                    .parse::<f32>()
-                    .map_err(|_| crate::error::ParseError::Header)?;
 
                 if (0f32..=1f32).contains(&q_value) {
                     quality = q_value;
                     raw_item = parts[1];
                 } else {
-                    return Err(crate::error::ParseError::Header);
+                    return Err(ParseError::Header);
                 }
             }
         }
 
-        let item = raw_item
+        let item = raw_item.parse::<T>().map_err(|_| ParseError::Header)?;
-            .parse::<T>()
-            .map_err(|_| crate::error::ParseError::Header)?;
 
         // we already checked above that the quality is within range
         Ok(QualityItem::new(item, Quality::from_f32(quality)))
@@ -224,7 +223,7 @@ mod tests {
         }
     }
 
-    impl str::FromStr for Encoding {
+    impl FromStr for Encoding {
         type Err = crate::error::ParseError;
         fn from_str(s: &str) -> Result<Encoding, crate::error::ParseError> {
             use Encoding::*;

src/middleware/compress.rs

@@ -2,10 +2,10 @@
 
 use std::{
     cmp,
+    convert::TryFrom,
     future::Future,
     marker::PhantomData,
     pin::Pin,
-    str::FromStr,
     task::{Context, Poll},
 };
 
@@ -13,16 +13,18 @@ use actix_http::{
     body::{MessageBody, ResponseBody},
     encoding::Encoder,
     http::header::{ContentEncoding, ACCEPT_ENCODING},
+    StatusCode,
 };
 use actix_service::{Service, Transform};
-use actix_utils::future::{ok, Ready};
+use actix_utils::future::{ok, Either, Ready};
 use futures_core::ready;
+use once_cell::sync::Lazy;
 use pin_project::pin_project;
 
 use crate::{
     dev::BodyEncoding,
     service::{ServiceRequest, ServiceResponse},
-    Error,
+    Error, HttpResponse,
 };
 
 /// Middleware for compressing response payloads.
@@ -78,34 +80,78 @@ pub struct CompressMiddleware<S> {
     encoding: ContentEncoding,
 }
 
+static SUPPORTED_ALGORITHM_NAMES: Lazy<String> = Lazy::new(|| {
+    let mut encoding = vec![];
+
+    #[cfg(feature = "compress-brotli")]
+    {
+        encoding.push("br");
+    }
+
+    #[cfg(feature = "compress-gzip")]
+    {
+        encoding.push("gzip");
+        encoding.push("deflate");
+    }
+
+    #[cfg(feature = "compress-zstd")]
+    encoding.push("zstd");
+
+    assert!(
+        !encoding.is_empty(),
+        "encoding can not be empty unless __compress feature has been explicitly enabled by itself"
+    );
+
+    encoding.join(", ")
+});
+
 impl<S, B> Service<ServiceRequest> for CompressMiddleware<S>
 where
-    B: MessageBody,
     S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
+    B: MessageBody,
 {
     type Response = ServiceResponse<ResponseBody<Encoder<B>>>;
     type Error = Error;
-    type Future = CompressResponse<S, B>;
+    type Future = Either<CompressResponse<S, B>, Ready<Result<Self::Response, Self::Error>>>;
 
     actix_service::forward_ready!(service);
 
     #[allow(clippy::borrow_interior_mutable_const)]
     fn call(&self, req: ServiceRequest) -> Self::Future {
         // negotiate content-encoding
-        let encoding = if let Some(val) = req.headers().get(&ACCEPT_ENCODING) {
+        let encoding_result = req
-            if let Ok(enc) = val.to_str() {
+            .headers()
-                AcceptEncoding::parse(enc, self.encoding)
+            .get(&ACCEPT_ENCODING)
-            } else {
+            .and_then(|val| val.to_str().ok())
-                ContentEncoding::Identity
+            .map(|enc| AcceptEncoding::try_parse(enc, self.encoding));
-            }
-        } else {
-            ContentEncoding::Identity
-        };
 
-        CompressResponse {
+        match encoding_result {
-            encoding,
+            // Missing header => fallback to identity
-            fut: self.service.call(req),
+            None => Either::left(CompressResponse {
-            _phantom: PhantomData,
+                encoding: ContentEncoding::Identity,
+                fut: self.service.call(req),
+                _phantom: PhantomData,
+            }),
+
+            // Valid encoding
+            Some(Ok(encoding)) => Either::left(CompressResponse {
+                encoding,
+                fut: self.service.call(req),
+                _phantom: PhantomData,
+            }),
+
+            // There is an HTTP header but we cannot match what client as asked for
+            Some(Err(_)) => {
+                let res = HttpResponse::with_body(
+                    StatusCode::NOT_ACCEPTABLE,
+                    SUPPORTED_ALGORITHM_NAMES.as_str(),
+                );
+                let enc = ContentEncoding::Identity;
+
+                Either::right(ok(req.into_response(res.map_body(move |head, body| {
+                    Encoder::response(enc, head, ResponseBody::Other(body.into()))
+                }))))
+            }
         }
     }
 }
@@ -114,7 +160,6 @@ where
 pub struct CompressResponse<S, B>
 where
     S: Service<ServiceRequest>,
-    B: MessageBody,
 {
     #[pin]
     fut: S::Future,
@@ -151,6 +196,7 @@ where
 
 struct AcceptEncoding {
     encoding: ContentEncoding,
+    // TODO: use Quality or QualityItem<ContentEncoding>
     quality: f64,
 }
 
@@ -177,26 +223,56 @@ impl PartialOrd for AcceptEncoding {
 
 impl PartialEq for AcceptEncoding {
     fn eq(&self, other: &AcceptEncoding) -> bool {
-        self.quality == other.quality
+        self.encoding == other.encoding && self.quality == other.quality
     }
 }
 
+/// Parse q-factor from quality strings.
+///
+/// If parse fail, then fallback to default value which is 1.
+/// More details available here: <https://developer.mozilla.org/en-US/docs/Glossary/Quality_values>
+fn parse_quality(parts: &[&str]) -> f64 {
+    for part in parts {
+        if part.trim().starts_with("q=") {
+            return part[2..].parse().unwrap_or(1.0);
+        }
+    }
+
+    1.0
+}
+
+#[derive(Debug, PartialEq, Eq)]
+enum AcceptEncodingError {
+    /// This error occurs when client only support compressed response and server do not have any
+    /// algorithm that match client accepted algorithms.
+    CompressionAlgorithmMismatch,
+}
+
 impl AcceptEncoding {
     fn new(tag: &str) -> Option<AcceptEncoding> {
         let parts: Vec<&str> = tag.split(';').collect();
         let encoding = match parts.len() {
             0 => return None,
-            _ => ContentEncoding::from(parts[0]),
+            _ => match ContentEncoding::try_from(parts[0]) {
-        };
+                Err(_) => return None,
-        let quality = match parts.len() {
+                Ok(x) => x,
-            1 => encoding.quality(),
+            },
-            _ => f64::from_str(parts[1]).unwrap_or(0.0),
         };
+
+        let quality = parse_quality(&parts[1..]);
+        if quality <= 0.0 || quality > 1.0 {
+            return None;
+        }
+
         Some(AcceptEncoding { encoding, quality })
     }
 
-    /// Parse a raw Accept-Encoding header value into an ordered list.
+    /// Parse a raw Accept-Encoding header value into an ordered list then return the best match
-    pub fn parse(raw: &str, encoding: ContentEncoding) -> ContentEncoding {
+    /// based on middleware configuration.
+    pub fn try_parse(
+        raw: &str,
+        encoding: ContentEncoding,
+    ) -> Result<ContentEncoding, AcceptEncodingError> {
         let mut encodings = raw
             .replace(' ', "")
             .split(',')
@@ -206,13 +282,90 @@ impl AcceptEncoding {
         encodings.sort();
 
         for enc in encodings {
-            if encoding == ContentEncoding::Auto {
+            if encoding == ContentEncoding::Auto || encoding == enc.encoding {
-                return enc.encoding;
+                return Ok(enc.encoding);
-            } else if encoding == enc.encoding {
-                return encoding;
             }
         }
 
-        ContentEncoding::Identity
+        // Special case if user cannot accept uncompressed data.
+        // See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding
+        // TODO: account for whitespace
+        if raw.contains("*;q=0") || raw.contains("identity;q=0") {
+            return Err(AcceptEncodingError::CompressionAlgorithmMismatch);
+        }
+
+        Ok(ContentEncoding::Identity)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    macro_rules! assert_parse_eq {
+        ($raw:expr, $result:expr) => {
+            assert_eq!(
+                AcceptEncoding::try_parse($raw, ContentEncoding::Auto),
+                Ok($result)
+            );
+        };
+    }
+
+    macro_rules! assert_parse_fail {
+        ($raw:expr) => {
+            assert!(AcceptEncoding::try_parse($raw, ContentEncoding::Auto).is_err());
+        };
+    }
+
+    #[test]
+    fn test_parse_encoding() {
+        // Test simple case
+        assert_parse_eq!("br", ContentEncoding::Br);
+        assert_parse_eq!("gzip", ContentEncoding::Gzip);
+        assert_parse_eq!("deflate", ContentEncoding::Deflate);
+        assert_parse_eq!("zstd", ContentEncoding::Zstd);
+
+        // Test space, trim, missing values
+        assert_parse_eq!("br,,,,", ContentEncoding::Br);
+        assert_parse_eq!("gzip  ,   br,   zstd", ContentEncoding::Gzip);
+
+        // Test float number parsing
+        assert_parse_eq!("br;q=1  ,", ContentEncoding::Br);
+        assert_parse_eq!("br;q=1.0  ,   br", ContentEncoding::Br);
+
+        // Test wildcard
+        assert_parse_eq!("*", ContentEncoding::Identity);
+        assert_parse_eq!("*;q=1.0", ContentEncoding::Identity);
+    }
+
+    #[test]
+    fn test_parse_encoding_qfactor_ordering() {
+        assert_parse_eq!("gzip, br, zstd", ContentEncoding::Gzip);
+        assert_parse_eq!("zstd, br, gzip", ContentEncoding::Zstd);
+
+        assert_parse_eq!("gzip;q=0.4, br;q=0.6", ContentEncoding::Br);
+        assert_parse_eq!("gzip;q=0.8, br;q=0.4", ContentEncoding::Gzip);
+    }
+
+    #[test]
+    fn test_parse_encoding_qfactor_invalid() {
+        // Out of range
+        assert_parse_eq!("gzip;q=-5.0", ContentEncoding::Identity);
+        assert_parse_eq!("gzip;q=5.0", ContentEncoding::Identity);
+
+        // Disabled
+        assert_parse_eq!("gzip;q=0", ContentEncoding::Identity);
+    }
+
+    #[test]
+    fn test_parse_compression_required() {
+        // Check we fallback to identity if there is an unsupported compression algorithm
+        assert_parse_eq!("compress", ContentEncoding::Identity);
+
+        // User do not want any compression
+        assert_parse_fail!("compress, identity;q=0");
+        assert_parse_fail!("compress, identity;q=0.0");
+        assert_parse_fail!("compress, *;q=0");
+        assert_parse_fail!("compress, *;q=0.0");
     }
 }

tests/test_server.rs

@@ -1077,3 +1077,22 @@ async fn test_data_drop() {
 
     assert_eq!(num.load(Ordering::SeqCst), 0);
 }
+
+#[actix_rt::test]
+async fn test_accept_encoding_no_match() {
+    let srv = actix_test::start_with(actix_test::config().h1(), || {
+        App::new()
+            .wrap(Compress::default())
+            .service(web::resource("/").route(web::to(move || HttpResponse::Ok().finish())))
+    });
+
+    let response = srv
+        .get("/")
+        .append_header((ACCEPT_ENCODING, "compress, identity;q=0"))
+        .no_decompress()
+        .send()
+        .await
+        .unwrap();
+
+    assert_eq!(response.status().as_u16(), 406);
+}