Mongoose get cookie value when there is only one element

[hoathienvu8x]

Mongoose get cookie value when there is only one element

When I set the cookie value devel=y and send it to the server with the code

/* GET / HTTP/1.0\r\nhost:127.0.0.1:5000\r\nCookie: devel=y\r\n\r\n */
struct mg_http_message *hm = (struct mg_http_message *)ev_data;
struct mg_str *cookie = mg_http_get_header(hm, "Cookie");
if (cookie) {
  struct mg_str devel = mg_http_get_header_var(
    *cookie, mg_str_n("devel", 5)
  );
  /* -> devel.len == 0 (Cookie: devel=y) */
  /* -> devel.len == 1 (Cookie: devel=y; X-visitor-id=Zrdm9lQ0Y5Q0FFVTZJ) */
  printf(
    "Cookie: %.*s\ndevel: %.*s\n",
    (int)cookie->len, cookie->buf,
    (int)devel.len, devel.buf
  );
}

The result I get is as follows:

Cookie: devel=y
devel:

But the cookie value of devel is y

[scaprile]

Let's see if I manage to understand you
Cookies here are irrelevant, what you are doing is trying to parse a text with a function to parse HTTP headers, and you seem to have success when there is more than one element of what you think it is valid (thing that you don't say but I guess from the title and the parts you commented out in your code), congratulations, and fail when there is only one, I'm sorry.
You are using a function that was written to parse HTTP headers, not text. If you succeed, congratulations, if you don't succeed, I'm sorry. Use a function written to parse text, the function you're calling was not meant to be used like that.
Please see our documentation, and follow the guidelines in our tutorials.
We handle cookies in a lot of our examples, please see them.

[hoathienvu8x]

Thanks @scaprile for replying, first of all I'm sorry for my bad English, I wrote a test code to simulate this because mongoose also uses such method to give the result when I use type cast from ev_data the test source code is as follows:

#include <stdio.h>
#include "mongoose.h"

void test_cookie(const char *s, size_t slen) {
  struct mg_http_message hm;
  struct mg_str *cookie, v;

  if (mg_http_parse(s, slen, &hm) != (int) slen) {
    printf("---\%s\n---\n\nmg_http_parse() failed\n", s);
    return;
  }
  cookie  = mg_http_get_header(&hm, "Cookie");
  if (!cookie) {
    printf("Cookie is null\n");
    return;
  }
  v = mg_http_get_header_var(
    *cookie, mg_str_n("devel", 5)
  );
  printf(
    "Cookie: %.*s\ndevel: %.*s\n",
    (int)cookie->len, cookie->buf,
    (int)v.len, v.buf
  );
}

int main() {
  const char *s =
    "GET / HTTP/1.0\r\nhost:127.0.0.1:5000\r\n"
    "Cookie: devel=y\r\n\r\n";
  test_cookie(s, strlen(s));
  s = 
    "GET / HTTP/1.0\r\nhost:127.0.0.1:5000\r\nCookie: "
    "devel=y; X-visitor-id=Zrdm9lQ0Y5Q0FFVTZJ\r\n\r\n";
  test_cookie(s, strlen(s));
  return 0;
}

I think the code needs to be checked at line 927 of file src/http.c in function mg_http_get_header_var but I don't know what to check and fix when s.len with v.len

[hoathienvu8x]

oh I see, that means this part needs to define an additional function to handle getting cookies, not calling the mg_http_get_header_var function from Mongoose source code, right?

[scaprile]

Do you mean this ? https://mongoose.ws/documentation/#mg_http_get_header_var
I see you seem to be following that doc guidance and using the _var function as shown there, and it doesn't work for you when you have just one variable inside your cookie. Is your cookie correctly formatted ? I see just text, not proper formatting. I mean:

It is not my main field of expertise, but in our examples, all variables inside a cookie end with a semicolon

Set-Cookie: devel=y;\r\n\r\n

mongoose/tutorials/http/device-dashboard/net.c

Lines 78 to 98 in 0f1a3cf

	static void handle_login(struct mg_connection *c, struct user *u) {
	char cookie[256];
	const char *cookie_name = c->is_tls ? "secure_access_token" : "access_token";
	mg_snprintf(cookie, sizeof(cookie),
	"Set-Cookie: %s=%s; Path=/; "
	"%sHttpOnly; SameSite=Lax; Max-Age=%d\r\n",
	cookie_name, u->access_token,
	c->is_tls ? "Secure; " : "", 3600 * 24);
	mg_http_reply(c, 200, cookie, "{%m:%m}", MG_ESC("user"), MG_ESC(u->name));
	}
	static void handle_logout(struct mg_connection *c) {
	char cookie[256];
	const char *cookie_name = c->is_tls ? "secure_access_token" : "access_token";
	mg_snprintf(cookie, sizeof(cookie),
	"Set-Cookie: %s=; Path=/; "
	"Expires=Thu, 01 Jan 1970 00:00:00 UTC; "
	"%sHttpOnly; Max-Age=0; \r\n", cookie_name,
	c->is_tls ? "Secure; " : "");
	mg_http_reply(c, 200, cookie, "true\n");
	}

[scaprile]

Can you provide authoritative formatting references saying othyerwise ?

[hoathienvu8x]

Thanks @scaprile for the example

After reading the feedback I wrote a function to handle getting the cookie value, because using chrome devtools and calling document.cookie = 'devel=y'; caused the source code on the server side to be empty and this is the code I defined and got the value

#include <stdio.h>
#include "mongoose.h"

struct mg_str mg_http_get_cookie(struct mg_http_message *hm, struct mg_str name) {
  struct mg_str *cookie = mg_http_get_header(hm, "Cookie");
  if (cookie) {
    struct mg_str entry, k, v;
    while (mg_span(*cookie, &entry, cookie, ';')) {
      if (
        mg_span(entry, &k, &v, '=') && name.len == k.len &&
        strncasecmp(name.buf, k.buf, k.len) == 0 /* mg_ncasecmp(name.buf, k.buf, k.len) */
      ) {
        char buf[256];
        size_t n = mg_url_decode(v.buf, v.len, buf, sizeof(buf), 1);
        return mg_str_n(buf, n);
      }
    }
  }
  return mg_str_n(NULL, 0);
}

void test_cookie(const char *s, size_t slen) {
  struct mg_http_message hm;
  struct mg_str *cookie, v;

  if (mg_http_parse(s, slen, &hm) != (int) slen) {
    printf("---\%s\n---\n\nmg_http_parse() failed\n", s);
    return;
  }
  v = mg_http_get_cookie(
    &hm, mg_str_n("devel", 5)
  );
  printf("devel: %.*s (%ld)\n", (int)v.len, v.buf, v.len);
}

int main() {
  const char *s =
    "GET / HTTP/1.0\r\nhost:127.0.0.1:5000\r\n"
    "Cookie: devel=y\r\n\r\n";
  test_cookie(s, strlen(s));
  s = 
    "GET / HTTP/1.0\r\nhost:127.0.0.1:5000\r\nCookie: "
    "devel=y; X-visitor-id=Zrdm9lQ0Y5Q0FFVTZJ\r\n\r\n";
  test_cookie(s, strlen(s));
  return 0;
}

Thanks @scaprile for the support, thank you very much @scaprile

[hoathienvu8x]

I hope the mg_http_get_cookie function can handle cases like when I used document.cookie = 'devel=y' when the client sent it, the server did not receive the value when the cookie only had one element (This is something I did not expect until I sent the response and knew the cause)