C parsing binary through recv - c

Question

I am Attempting to download a binary file(exe) from a php script. Been stuck for hours.
PHP Script:
header("Content-type: application/octet-stream");
header("Content-Disposition: filename=\"".$path_parts["basename"]."\"");
header("Content-length: $fsize");
header("Cache-control: private"); //use this to open files directly
while(!feof($fd)) {
$buffer = fread($fd, 1048);
echo $buffer;
}
C:
char update[1024] = {0};
FILE *fileo;
fileo = fopen("test.exe", "wb");
instruction = recv(s, update, 1024, 0);
int result =returnBody();//Removes headers
fwrite(body, sizeof(body),1,fileo);
memset(update, 0, 1024);
while ((instruction = recv(s, update, 1024, 0)) > 0)
{
fwrite(update, sizeof(update),1,fileo);
memset(update, 0, 1024);
}
fclose(fileo);
returnbody function:
int returnBody(){
for(int x = 0; x < strlen(message); x++)
{
if(message[x] == '\r')
{
if(message[x + 1] == '\n')
{
if(message[x + 2] == '\r')
{
if(message[x + 3] == '\n')
{
int y = x + 4;
body = (char *)realloc(body, ((strlen(message) - y) * sizeof(char)));
memset(body, 0, sizeof(body));
for(int b = 0; y < strlen(message); y++, b++){
body[b] = message[y];
}
return 1;
}
}
}
}
}
return 0;
}
I succeed in writing the file but it doesn't run. Gets an error, unsupported
16 bit application.
My Question is do I need to parse it as binary before I write it to the file?

Answer 1

As pointed in comments:
you can't use strlen when using binary data
you can't use sizeof when using pointers on array.
Lets see:
/* you should have some static variables to store data */
static void * body = NULL;
size_t body_size = 0;
/* extract body from message */
int returnBody(void *message, size_t message_size){
if (! message || message_size < 5)
{
return 0;
}
/* if your system doesn't have memmem function, see https://stackoverflow.com/a/52989329/1212012 */
void *data = memmem(message, message_size, "\r\n\r\n", 4);
if (data) {
/* header found */
/* data are four bytes after the \r\n\r\n sequence */
data += 4;
size_t header_size = data - message;
body_size = message_size - header_size;
void *p = realloc(body, body_size);
if (!p) {
perror("realloc");
return 0;
}
body = p;
memcpy(body, data, body_size);
return 1;
}
return 0;
}
And your reading writting function should be like:
char update[1024] = {0};
FILE *fileo;
fileo = fopen("test.exe", "wb");
/* you should test `fileo` here */
/* first read */
instruction = recv(s, update, sizeof update, 0);
/* set message and its size for */
int result =returnBody(udpate, instruction);//Removes headers
/* you should test `result` here */
fwrite(body, body_size, 1, fileo);
/* clearing update is not necessary */
/*memset(update, 0, sizeof update); */
while ((instruction = recv(s, update, sizeof update, 0)) > 0)
{
fwrite(update, instruction, 1, fileo);
//memset(update, 0, sizeof update);
}
fclose(fileo);