Improve Transfer-Encoding handling (squid-cache#702)

Reject messages containing Transfer-Encoding header with coding other
than chunked or identity. Squid does not support other codings.

For simplicity and security sake, also reject messages where
Transfer-Encoding contains unnecessary complex values that are
technically equivalent to "chunked" or "identity" (e.g., ",,chunked" or
"identity, chunked").

RFC 7230 formally deprecated and removed identity coding, but it is
still used by some agents.

src/HttpHeader.cc

@@ -174,6 +174,7 @@ HttpHeader::operator =(const HttpHeader &other)
         update(&other); // will update the mask as well
         len = other.len;
         conflictingContentLength_ = other.conflictingContentLength_;
+        teUnsupported_ = other.teUnsupported_;
     }
     return *this;
 }
@@ -222,6 +223,7 @@ HttpHeader::clean()
     httpHeaderMaskInit(&mask, 0);
     len = 0;
     conflictingContentLength_ = false;
+    teUnsupported_ = false;
     PROF_stop(HttpHeaderClean);
 }
 
@@ -471,11 +473,23 @@ HttpHeader::parse(const char *header_start, size_t hdrLen)
                Raw("header", header_start, hdrLen));
     }
 
-    if (chunked()) {
+    String rawTe;
+    if (getByIdIfPresent(Http::HdrType::TRANSFER_ENCODING, &rawTe)) {
         // RFC 2616 section 4.4: ignore Content-Length with Transfer-Encoding
         // RFC 7230 section 3.3.3 #3: Transfer-Encoding overwrites Content-Length
         delById(Http::HdrType::CONTENT_LENGTH);
         // and clen state becomes irrelevant
+
+        if (rawTe == "chunked") {
+            ; // leave header present for chunked() method
+        } else if (rawTe == "identity") { // deprecated. no coding
+            delById(Http::HdrType::TRANSFER_ENCODING);
+        } else {
+            // This also rejects multiple encodings until we support them properly.
+            debugs(55, warnOnError, "WARNING: unsupported Transfer-Encoding used by client: " << rawTe);
+            teUnsupported_ = true;
+        }
+
     } else if (clen.sawBad) {
         // ensure our callers do not accidentally see bad Content-Length values
         delById(Http::HdrType::CONTENT_LENGTH);

src/HttpHeader.h

@@ -140,7 +140,13 @@ class HttpHeader
     int hasListMember(Http::HdrType id, const char *member, const char separator) const;
     int hasByNameListMember(const char *name, const char *member, const char separator) const;
     void removeHopByHopEntries();
-    inline bool chunked() const; ///< whether message uses chunked Transfer-Encoding
+
+    /// whether the message uses chunked Transfer-Encoding
+    /// optimized implementation relies on us rejecting/removing other codings
+    bool chunked() const { return has(Http::HdrType::TRANSFER_ENCODING); }
+
+    /// whether message used an unsupported and/or invalid Transfer-Encoding
+    bool unsupportedTe() const { return teUnsupported_; }
 
     /* protected, do not use these, use interface functions instead */
     std::vector<HttpHeaderEntry *> entries;     /**< parsed fields in raw format */
@@ -158,6 +164,9 @@ class HttpHeader
 private:
     HttpHeaderEntry *findLastEntry(Http::HdrType id) const;
     bool conflictingContentLength_; ///< found different Content-Length fields
+    /// unsupported encoding, unnecessary syntax characters, and/or
+    /// invalid field-value found in Transfer-Encoding header
+    bool teUnsupported_ = false;
 };
 
 int httpHeaderParseQuotedString(const char *start, const int len, String *val);
@@ -167,13 +176,6 @@ SBuf httpHeaderQuoteString(const char *raw);
 
 void httpHeaderCalcMask(HttpHeaderMask * mask, Http::HdrType http_hdr_type_enums[], size_t count);
 
-inline bool
-HttpHeader::chunked() const
-{
-    return has(Http::HdrType::TRANSFER_ENCODING) &&
-           hasListMember(Http::HdrType::TRANSFER_ENCODING, "chunked", ',');
-}
-
 void httpHeaderInitModule(void);
 
 #endif /* SQUID_HTTPHEADER_H */

src/client_side.cc

@@ -1600,9 +1600,7 @@ void
 clientProcessRequest(ConnStateData *conn, const Http1::RequestParserPointer &hp, Http::Stream *context)
 {
     ClientHttpRequest *http = context->http;
-    bool chunked = false;
     bool mustReplyToOptions = false;
-    bool unsupportedTe = false;
     bool expectBody = false;
 
     // We already have the request parsed and checked, so we
@@ -1659,13 +1657,7 @@ clientProcessRequest(ConnStateData *conn, const Http1::RequestParserPointer &hp,
         request->http_ver.minor = http_ver.minor;
     }
 
-    if (request->header.chunked()) {
-        chunked = true;
-    } else if (request->header.has(Http::HdrType::TRANSFER_ENCODING)) {
-        const String te = request->header.getList(Http::HdrType::TRANSFER_ENCODING);
-        // HTTP/1.1 requires chunking to be the last encoding if there is one
-        unsupportedTe = te.size() && te != "identity";
-    } // else implied identity coding
+    const auto unsupportedTe = request->header.unsupportedTe();
 
     mustReplyToOptions = (request->method == Http::METHOD_OPTIONS) &&
                          (request->header.getInt64(Http::HdrType::MAX_FORWARDS) == 0);
@@ -1682,6 +1674,7 @@ clientProcessRequest(ConnStateData *conn, const Http1::RequestParserPointer &hp,
         return;
     }
 
+    const auto chunked = request->header.chunked();
     if (!chunked && !clientIsContentLengthValid(request.getRaw())) {
         clientStreamNode *node = context->getClientReplyContext();
         clientReplyContext *repContext = dynamic_cast<clientReplyContext *>(node->data.getRaw());

src/http.cc

@@ -1292,6 +1292,9 @@ HttpStateData::continueAfterParsingHeader()
             } else if (vrep->header.conflictingContentLength()) {
                 fwd->dontRetry(true);
                 error = ERR_INVALID_RESP;
+            } else if (vrep->header.unsupportedTe()) {
+                fwd->dontRetry(true);
+                error = ERR_INVALID_RESP;
             } else {
                 return true; // done parsing, got reply, and no error
             }