Fix issues around multi-line headers

Always discard leading whitespace in a header value, even if it
is folded.

Pay attention to values of interesting headers (Connection,
Content-Length, etc.) even when they come on a continuation line.

Add a test case to check that requests and responses using only LF
to separate lines are handled correctly.

http_parser.c

@@ -281,6 +281,8 @@ enum state
   , s_header_field_start
   , s_header_field
   , s_header_value_discard_ws
+  , s_header_value_discard_ws_almost_done
+  , s_header_value_discard_lws
   , s_header_value_start
   , s_header_value
   , s_header_value_lws
@@ -1404,28 +1406,26 @@ size_t http_parser_execute (http_parser *parser,
 
       case s_header_value_discard_ws:
         if (ch == ' ' || ch == '\t') break;
-        /* FALLTHROUGH */
-
-      case s_header_value_start:
-      {
-        MARK(header_value);
-
-        parser->state = s_header_value;
-        parser->index = 0;
 
         if (ch == CR) {
-          parser->header_state = h_general;
-          parser->state = s_header_almost_done;
-          CALLBACK_DATA(header_value);
+          parser->state = s_header_value_discard_ws_almost_done;
           break;
         }
 
         if (ch == LF) {
-          parser->state = s_header_field_start;
-          CALLBACK_DATA(header_value);
+          parser->state = s_header_value_discard_lws;
           break;
         }
 
+        /* FALLTHROUGH */
+
+      case s_header_value_start:
+      {
+        MARK(header_value);
+
+        parser->state = s_header_value;
+        parser->index = 0;
+
         c = LOWER(ch);
 
         switch (parser->header_state) {
@@ -1573,7 +1573,17 @@ size_t http_parser_execute (http_parser *parser,
         STRICT_CHECK(ch != LF);
 
         parser->state = s_header_value_lws;
+        break;
+      }
 
+      case s_header_value_lws:
+      {
+        if (ch == ' ' || ch == '\t') {
+          parser->state = s_header_value_start;
+          goto reexecute_byte;
+        }
+
+        /* finished the header */
         switch (parser->header_state) {
           case h_connection_keep_alive:
             parser->flags |= F_CONNECTION_KEEP_ALIVE;
@@ -1588,17 +1598,29 @@ size_t http_parser_execute (http_parser *parser,
             break;
         }
 
+        parser->state = s_header_field_start;
+        goto reexecute_byte;
+      }
+
+      case s_header_value_discard_ws_almost_done:
+      {
+        STRICT_CHECK(ch != LF);
+        parser->state = s_header_value_discard_lws;
         break;
       }
 
-      case s_header_value_lws:
+      case s_header_value_discard_lws:
       {
-        if (ch == ' ' || ch == '\t')
-          parser->state = s_header_value_start;
-        else
+        if (ch == ' ' || ch == '\t') {
+          parser->state = s_header_value_discard_ws;
+          break;
+        } else {
+          /* header value was empty */
+          MARK(header_value);
           parser->state = s_header_field_start;
-
-        goto reexecute_byte;
+          CALLBACK_DATA_NOADVANCE(header_value);
+          goto reexecute_byte;
+        }
       }
 
       case s_headers_almost_done:

test.c

@@ -608,8 +608,14 @@ const struct message requests[] =
          "  mno \r\n"
          "\t \tqrs\r\n"
          "Line2: \t line2\t\r\n"
+         "Line3:\r\n"
+         " line3\r\n"
+         "Line4: \r\n"
+         " \r\n"
+         "Connection:\r\n"
+         " close\r\n"
          "\r\n"
-  ,.should_keep_alive= TRUE
+  ,.should_keep_alive= FALSE
   ,.message_complete_on_eof= FALSE
   ,.http_major= 1
   ,.http_minor= 1
@@ -618,9 +624,12 @@ const struct message requests[] =
   ,.fragment= ""
   ,.request_path= "/"
   ,.request_url= "/"
-  ,.num_headers= 2
+  ,.num_headers= 5
   ,.headers= { { "Line1", "abc\tdef ghi\t\tjkl  mno \t \tqrs" }
              , { "Line2", "line2\t" }
+             , { "Line3", "line3" }
+             , { "Line4", "" }
+             , { "Connection", "close" },
              }
   ,.body= ""
   }
@@ -904,6 +913,43 @@ const struct message requests[] =
   ,.body= ""
   }
 
+#define LINE_FOLDING_IN_HEADER_WITH_LF 34
+, {.name= "line folding in header value"
+  ,.type= HTTP_REQUEST
+  ,.raw= "GET / HTTP/1.1\n"
+         "Line1:   abc\n"
+         "\tdef\n"
+         " ghi\n"
+         "\t\tjkl\n"
+         "  mno \n"
+         "\t \tqrs\n"
+         "Line2: \t line2\t\n"
+         "Line3:\n"
+         " line3\n"
+         "Line4: \n"
+         " \n"
+         "Connection:\n"
+         " close\n"
+         "\n"
+  ,.should_keep_alive= FALSE
+  ,.message_complete_on_eof= FALSE
+  ,.http_major= 1
+  ,.http_minor= 1
+  ,.method= HTTP_GET
+  ,.query_string= ""
+  ,.fragment= ""
+  ,.request_path= "/"
+  ,.request_url= "/"
+  ,.num_headers= 5
+  ,.headers= { { "Line1", "abc\tdef ghi\t\tjkl  mno \t \tqrs" }
+             , { "Line2", "line2\t" }
+             , { "Line3", "line3" }
+             , { "Line4", "" }
+             , { "Connection", "close" },
+             }
+  ,.body= ""
+  }
+
 
 , {.name= NULL } /* sentinel */
 };