[lwip-devel] [PATCH lwip-contrib] httpd_raw: fix detection of Content-Length header

[Michael Heimpold]

HTTP headers are case-insensitive, so using strnstr to find the Content-Length
header fails with browsers which use other case variants that the one defined
in the code.

To get this work correctly, we need a strncasestr function which might not
be available on some platforms. Thus, we need to define one ourself, upon
user request. Use existing code as much as possible for this.

Signed-off-by: Michael Heimpold <address@hidden>
---

Hi,

I found this tiny bug, when using this great project for the first time.
Thank you all for all your hard work.

Since this is my first contribution, please tell me, whether this is
the correct way to submit bugfixes and/or how to improve this submission :)

Best regards,
Michael

 apps/httpserver_raw/httpd.c |   37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/apps/httpserver_raw/httpd.c b/apps/httpserver_raw/httpd.c
index d0c3420..3ebdc67 100644
--- a/apps/httpserver_raw/httpd.c
+++ b/apps/httpserver_raw/httpd.c
@@ -143,6 +143,11 @@
 #define LWIP_HTTPD_STRNSTR_PRIVATE          1
 #endif
 
+/** Set this to 1 on platforms where strncasestr is not available */
+#ifndef LWIP_HTTPD_STRNCASESTR_PRIVATE
+#define LWIP_HTTPD_STRNCASESTR_PRIVATE      1
+#endif
+
 /** Set this to one to show error pages when parsing a request fails instead
     of simply closing the connection. */
 #ifndef LWIP_HTTPD_SUPPORT_EXTSTATUS
@@ -431,10 +436,12 @@ int g_iNumCGIs;
 static struct http_state *http_connections;
 #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
 
-#if LWIP_HTTPD_STRNSTR_PRIVATE
-/** Like strstr but does not need 'buffer' to be NULL-terminated */
+#if LWIP_HTTPD_STRNSTR_PRIVATE || LWIP_HTTPD_STRNCASESTR_PRIVATE
+/** Typedef to simplify the last argument type for following function */
+typedef int (*strncmp_func_t)(const char *s1, const char *s2, size_t n);
+
 static char*
-strnstr(const char* buffer, const char* token, size_t n)
+__lwip_strnxstr(const char* buffer, const char* token, size_t n, 
strncmp_func_t cmpfunc)
 {
   const char* p;
   int tokenlen = (int)strlen(token);
@@ -442,12 +449,30 @@ strnstr(const char* buffer, const char* token, size_t n)
     return (char *)buffer;
   }
   for (p = buffer; *p && (p + tokenlen <= buffer + n); p++) {
-    if ((*p == *token) && (strncmp(p, token, tokenlen) == 0)) {
+    if ((*p == *token) && (cmpfunc(p, token, tokenlen) == 0)) {
       return (char *)p;
     }
   }
   return NULL;
-} 
+}
+
+#if LWIP_HTTPD_STRNSTR_PRIVATE
+/** Like strstr but does not need 'buffer' to be NULL-terminated */
+static inline char*
+strnstr(const char* buffer, const char* token, size_t n)
+{
+  return __lwip_strnxstr(buffer, token, n, strncmp);
+}
+#endif /* LWIP_HTTPD_STRNSTR_PRIVATE */
+
+#if LWIP_HTTPD_STRNCASESTR_PRIVATE
+/** Like strcasestr but does not need 'buffer' to be NULL-terminated */
+static inline char*
+strncasestr(const char* buffer, const char* token, size_t n)
+{
+  return __lwip_strnxstr(buffer, token, n, strncasecmp);
+}
+#endif /* LWIP_HTTPD_STRNCASESTR_PRIVATE */
 #endif /* LWIP_HTTPD_STRNSTR_PRIVATE */
 
 #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
@@ -1753,7 +1778,7 @@ http_post_request(struct pbuf *inp, struct http_state *hs,
 #define HTTP_HDR_CONTENT_LEN                "Content-Length: "
 #define HTTP_HDR_CONTENT_LEN_LEN            16
 #define HTTP_HDR_CONTENT_LEN_DIGIT_MAX_LEN  10
-    char *scontent_len = strnstr(uri_end + 1, HTTP_HDR_CONTENT_LEN, crlfcrlf - 
(uri_end + 1));
+    char *scontent_len = strncasestr(uri_end + 1, HTTP_HDR_CONTENT_LEN, 
crlfcrlf - (uri_end + 1));
     if (scontent_len != NULL) {
       char *scontent_len_end = strnstr(scontent_len + 
HTTP_HDR_CONTENT_LEN_LEN, CRLF, HTTP_HDR_CONTENT_LEN_DIGIT_MAX_LEN);
       if (scontent_len_end != NULL) {
-- 
1.7.10.4