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h0mbre/vuln.c

Created Jun 14, 2020
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/mman.h>
struct ORIGINAL_FILE {
char * data;
size_t length;
};
struct ORIGINAL_FILE get_bytes(char* fileName) {
FILE *filePtr;
char* buffer;
long fileLen;
filePtr = fopen(fileName, "rb");
if (!filePtr) {
printf("[>] Unable to open %s\n", fileName);
exit(-1);
}
if (fseek(filePtr, 0, SEEK_END)) {
printf("[>] fseek() failed, wtf?\n");
exit(-1);
}
fileLen = ftell(filePtr);
if (fileLen == -1) {
printf("[>] ftell() failed, wtf?\n");
exit(-1);
}
errno = 0;
rewind(filePtr);
if (errno) {
printf("[>] rewind() failed, wtf?\n");
exit(-1);
}
long trueSize = fileLen * sizeof(char);
printf("[>] %s is %ld bytes.\n", fileName, trueSize);
buffer = (char *)malloc(fileLen * sizeof(char));
fread(buffer, fileLen, 1, filePtr);
fclose(filePtr);
struct ORIGINAL_FILE original_file;
original_file.data = buffer;
original_file.length = trueSize;
return original_file;
}
void check_one(char* buffer, int check) {
if (buffer[check] == '\x6c') {
return;
}
else {
printf("[>] Check 1 failed.\n");
exit(-1);
}
}
void check_two(char* buffer, int check) {
if (buffer[check] == '\x57') {
return;
}
else {
printf("[>] Check 2 failed.\n");
exit(-1);
}
}
void check_three(char* buffer, int check) {
if (buffer[check] == '\x21') {
return;
}
else {
printf("[>] Check 3 failed.\n");
exit(-1);
}
}
void vuln(char* buffer, size_t length) {
printf("[>] Passed all checks!\n");
char vulnBuff[20];
memcpy(vulnBuff, buffer, length);
}
int main(int argc, char *argv[]) {
/*
if (argc < 2 || argc > 2) {
printf("[>] Usage: vuln example.txt\n");
exit(-1);
}
char *filename = argv[1];
*/
char *filename = "Canon_40D.jpg";
printf("[>] Analyzing file: %s.\n", filename);
struct ORIGINAL_FILE original_file = get_bytes(filename);
int checkNum1 = (int)(original_file.length * .33);
printf("[>] Check 1 no.: %d\n", checkNum1);
int checkNum2 = (int)(original_file.length * .5);
printf("[>] Check 2 no.: %d\n", checkNum2);
int checkNum3 = (int)(original_file.length * .67);
printf("[>] Check 3 no.: %d\n", checkNum3);
check_one(original_file.data, checkNum1);
check_two(original_file.data, checkNum2);
check_three(original_file.data, checkNum3);
vuln(original_file.data, original_file.length);
return 0;
}
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