more robust chunked response parsing (fixes #2554)

handle chunked parts across multiple reads

fixes https://redmine.lighttpd.net/issues/2554
where Happstack performs multiple writes to send HTTP chunked header,
HTTP chunked body, and CRLF ending HTTP chunked body

supercedes #8

handle additional chunked case of split CR and LF
reference
  https://github.com/lighttpd/weighttp/pull/9/files#r52358620
  thx stbuehler

detect CR not followed by LF (error)

handle NIL in chunked stream
(should not occur in HTTP headers or chunked header,
 but could occur in chunked body)

x-ref:
  "weighttp closing connection too early(?)"
  https://redmine.lighttpd.net/issues/2554

github: closes #8, closes #9

src/client.c

@@ -337,6 +337,11 @@ static uint8_t client_parse(Client *client, int size) {
 				status_code += *str - '0';
 			}
 
+			// look for next \r\n
+			end = memchr(end, '\r', client->buffer_offset);
+			if (!end || *(end+1) != '\n')
+				return (!end || *(end+1) == '\0') && client->buffer_offset < 1024 ? 1 : 0;
+
 			if (status_code >= 200 && status_code < 300) {
 				client->worker->stats.req_2xx++;
 				client->status_success = 1;
@@ -352,19 +357,14 @@ static uint8_t client_parse(Client *client, int size) {
 				return 0;
 			}
 
-			// look for next \r\n
-			end = strchr(end, '\r');
-			if (!end || *(end+1) != '\n')
-				return 0;
-
 			client->parser_offset = end + 2 - client->buffer;
 			client->parser_state = PARSER_HEADER;
 		case PARSER_HEADER:
 			//printf("parse (HEADER)\n");
 			/* look for Content-Length and Connection header */
-			while (NULL != (end = strchr(&client->buffer[client->parser_offset], '\r'))) {
+			while (NULL != (end = memchr(&client->buffer[client->parser_offset], '\r', client->buffer_offset - client->parser_offset))) {
 				if (*(end+1) != '\n')
-					return 0;
+					return *(end+1) == '\0' && client->buffer_offset - client->parser_offset < 1024 ? 1 : 0;
 
 				if (end == &client->buffer[client->parser_offset]) {
 					/* body reached */
@@ -449,25 +449,33 @@ static uint8_t client_parse(Client *client, int size) {
 						else if (*str >= 'a' && *str <= 'z')
 							client->chunk_size += 10 + *str - 'a';
 						else
-							return 0;
+							return 0; /*(src < end checked above)*/
 					}
 
-					str = strstr(str, "\r\n");
-					if (!str)
-						return 0;
+					if (str[0] != '\r') {
+						str = memchr(str, '\r', end-str);
+						if (!str) {
+							client->chunk_size = -1;
+							return size < 1024 ? 1 : 0;
+						}
+					}
+					if (str[1] != '\n') {
+						client->chunk_size = -1;
+						return str+1 == end ? 1 : 0;
+					}
 					str += 2;
 
 					//printf("---------- chunk size: %"PRIi64", %d read, %d offset, data: '%s'\n", client->chunk_size, size, client->parser_offset, str);
 
+					size -= str - &client->buffer[client->parser_offset];
+					client->parser_offset = str - client->buffer;
+
 					if (client->chunk_size == 0) {
 						/* chunk of size 0 marks end of content body */
 						client->state = CLIENT_END;
 						client->success = client->status_success ? 1 : 0;
 						return 1;
 					}
-
-					size -= str - &client->buffer[client->parser_offset];
-					client->parser_offset = str - client->buffer;
 				}
 
 				/* consume chunk till chunk_size is reached */
@@ -482,6 +490,9 @@ static uint8_t client_parse(Client *client, int size) {
 				//printf("---------- chunk consuming: %d, received: %"PRIi64" of %"PRIi64", offset: %d\n", consume_max, client->chunk_received, client->chunk_size, client->parser_offset);
 
 				if (client->chunk_received == client->chunk_size) {
+					if (size - consume_max < 2)
+						return 1;
+
 					if (client->buffer[client->parser_offset] != '\r' || client->buffer[client->parser_offset+1] != '\n')
 						return 0;