Skip trailer fields after the last chunk, and answer 400 to a bare LF in them

src/ChunkedEncoding.h

@@ -203,6 +203,7 @@ namespace uWS {
                     if (chunkSize(state) == 0) {
                         // Start of line: \r means final empty line, else it's a trailer header
                         if (c == '\r') state = (state & ~STATE_SIZE_MASK) | 1;
+                        else if (c == '\n') { state = STATE_IS_ERROR; return std::nullopt; }
                         else state = (state & ~STATE_SIZE_MASK) | 2;
                     } else if (chunkSize(state) == 1) {
                         // Expecting \n of final empty line
@@ -215,6 +216,7 @@ namespace uWS {
                     } else if (chunkSize(state) == 2) {
                         // Inside trailer header, wait for \r
                         if (c == '\r') state = (state & ~STATE_SIZE_MASK) | 3;
+                        else if (c == '\n') { state = STATE_IS_ERROR; return std::nullopt; }
                     } else if (chunkSize(state) == 3) {
                         // Expecting \n to terminate the header line
                         if (c == '\n') state = (state & ~STATE_SIZE_MASK) | 0;

src/HttpParser.h

@@ -610,7 +610,7 @@ struct HttpParser {
                 if (!CONSUME_MINIMALLY) {
                     /* Go ahead and parse it (todo: better heuristics for emitting FIN to the app level) */
                     std::string_view dataToConsume(data, length);
-                    for (auto chunk : uWS::ChunkIterator(&dataToConsume, &remainingStreamingBytes)) {
+                    for (auto chunk : uWS::ChunkIterator(&dataToConsume, &remainingStreamingBytes, true)) {
                         dataHandler(user, chunk, chunk.length() ? UINT64_MAX : 0);
                     }
                     if (isParsingInvalidChunkedEncoding(remainingStreamingBytes)) {
@@ -672,7 +672,7 @@ struct HttpParser {
             /* It's either chunked or with a content-length */
             if (isParsingChunkedEncoding(remainingStreamingBytes)) {
                 std::string_view dataToConsume(data, length);
-                for (auto chunk : uWS::ChunkIterator(&dataToConsume, &remainingStreamingBytes)) {
+                for (auto chunk : uWS::ChunkIterator(&dataToConsume, &remainingStreamingBytes, true)) {
                     /* If we got the zero size chunk, maxRemainingBodyLength is 0, else it is practically infinity */
                     dataHandler(user, chunk, chunk.length() ? UINT64_MAX : 0);
                 }
@@ -730,7 +730,7 @@ struct HttpParser {
                     /* It's either chunked or with a content-length */
                     if (isParsingChunkedEncoding(remainingStreamingBytes)) {
                         std::string_view dataToConsume(data, length);
-                        for (auto chunk : uWS::ChunkIterator(&dataToConsume, &remainingStreamingBytes)) {
+                        for (auto chunk : uWS::ChunkIterator(&dataToConsume, &remainingStreamingBytes, true)) {
                             dataHandler(user, chunk, chunk.length() ? UINT64_MAX : 0);
                         }
                         if (isParsingInvalidChunkedEncoding(remainingStreamingBytes)) {

tests/HttpParser.cpp

@@ -36,6 +36,41 @@ int main() {
 
     std::cout << "HTTP DONE" << std::endl;
 
+    /* RFC 9112 7.1.2: trailer fields after the last chunk are skipped and the next request still parses.
+     * A bare LF there is a 400, else the next request would be read as a trailer field */
+    struct {
+        const char *trailer;
+        bool accept;
+    } trailerCases[] = {
+        {"X-Checksum: abc\r\n\r\n", true},
+        {"\n", false},
+        {"X-Checksum: abc\n\r\n", false},
+    };
+
+    for (auto &c : trailerCases) {
+        std::string req = std::string("POST / HTTP/1.1\r\nHost: 127.0.0.1\r\nTransfer-Encoding: chunked\r\n\r\n5\r\nhello\r\n0\r\n") + c.trailer
+                          + "GET / HTTP/1.1\r\nHost: 127.0.0.1\r\n\r\n";
+        unsigned int length = (unsigned int) req.size();
+        req.append(32, 'E');
+
+        int requests = 0;
+        void *trailerUser = (void *) 13;
+        uWS::HttpParser trailerParser;
+        auto [trailerErr, trailerReturned] = trailerParser.consumePostPadded(req.data(), length, trailerUser, nullptr, [&requests](void *s, uWS::HttpRequest *) -> void * {
+            requests++;
+            return s;
+        }, [](void *s, std::string_view, bool) -> void * {
+            return s;
+        });
+
+        bool ok = c.accept ? (trailerReturned == trailerUser && requests == 2) : trailerReturned != trailerUser;
+        if (!ok) {
+            std::cerr << "Trailer \"" << c.trailer << "\" expected " << (c.accept ? "accept" : "400")
+                      << ", got err=" << trailerErr << " requests=" << requests << std::endl;
+            return 1;
+        }
+    }
+
     /* Issue 1941: accept Transfer-Encoding when the final coding is chunked (case-insensitive). */
     struct {
         const char *te;