用c写的web应用程序的笔测试

Question

我需要对IT学校项目进行笔试。这是执行登录的代码。任何人都可以解释我如何绕过这段代码。

#include <stdio.h>
#include "utils.h"
#include <string.h>
#include <stdlib.h>

void main()
{
size_t length = 0;
char * line = NULL;
char user_name[35];
char attempt_password[35];
char tokenbuffer[64];
char tokenbuffer2[64];
char * method;
char password_from_db[64];
FILE * f;

method = getenv("REQUEST_METHOD");
if(strcmp(method, "POST") == 0)
{
    getline(&line, &length, stdin);
}
else
{
    line = getenv("QUERY_STRING");
}
strcpy(user_name, post_value(line, "user_name"));
strcpy(attempt_password, post_value(line, "password"));

if (strstr(user_name, "&") != NULL)
    strstr(user_name, "&")[0] = 0;

if (strstr(attempt_password, "&") != NULL)
    strstr(attempt_password, "&")[0] = 0;

if (strstr(attempt_password, "\n") != NULL)
    strstr(attempt_password, "\n")[0] = 0;

sprintf(tokenbuffer, "../../db/pass_%s", user_name);
f = fopen(tokenbuffer, "r");
if (f != NULL)
{
    getline(&line, &length, f);
    strcpy(password_from_db, line);

    if (strncmp(attempt_password, password_from_db, strlen(attempt_password)) == 0)
    {
        hexify_string(user_name, tokenbuffer);
        printf("Set-cookie: access_token=%s; Path=/;\n", tokenbuffer);
        redirect("/cgi-bin/show/landing");
        headers();

        printf("access_token=%s\n", tokenbuffer);
    }
    else
    {
        headers();
        printf("Wrong!\n");
    }
}
else
{
    headers();
    printf("User not into existing\n");
}
}

这里可以使用什么样的注射攻击。请解释一下，我是新手。提前致谢