/* Sebastian Büttner <sebastian.buettner@iem.thm.de>
 * GNU GPLv3
 */

#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>

#define READ_FD pipefd[0]
#define WRITE_FD pipefd[1]
#define PHP "php"
#define BUFFER_SIZE 0x200

int main(int argc, char *argv[])
{
    pid_t child_pid;
    int pipefd[2], fd, bytes_read, total_bytes_read, bytes_to_read,
        bytes_executed, total_bytes_executed,
        stop = 0, match = 1;
    char *filename;
    char buffer_read[BUFFER_SIZE], buffer_execute[BUFFER_SIZE];

    if (argc < 2) {
        dprintf(STDERR_FILENO, "Usage: phpce file\n");
        return 1;
    }
    filename = argv[1];

    if (pipe(pipefd) < 0) {
        perror("Unable to create pipe");
        return 1;
    }

    if (fcntl(pipefd[0], F_SETFD, FD_CLOEXEC) == -1) {
        perror("fcntl()");
        return 1;
    }

    switch (child_pid = fork()) {
        case 0:
            /* Child */
            close(READ_FD);
            dup2(WRITE_FD, STDOUT_FILENO);
            close(WRITE_FD);
            execlp(PHP, PHP, "-f", filename, NULL);
            break;

        default:
            /* Parent */
            close(WRITE_FD);
            if ((fd = open(filename, O_RDONLY)) < 0) {
                perror("Unable to open file for reading");
                kill(child_pid, SIGKILL);
                return 1;
            }

            total_bytes_read = 0;
            total_bytes_executed = 0;
            while (!stop) {
                /* Read a chunk from the php process */
                if ((bytes_executed = read(READ_FD, buffer_execute, BUFFER_SIZE)) > 0)
                {
                    total_bytes_executed += bytes_executed;
                    /* Read as many bytes as we got through the pipe in last invocation */
                    bytes_to_read = bytes_executed;
                    do {
                        if ((bytes_read = read(fd, buffer_read, bytes_to_read)) > 0)
                        {
                            total_bytes_read += bytes_read;
                            bytes_to_read -= bytes_read;
                        } else
                        {
                            /* End of file */
                            stop = 1;
                            break;
                        }
                    } while (bytes_to_read);

                    /* Compare both chunks */
                    if (memcmp(buffer_execute, buffer_read, bytes_executed) == 0)
                        continue;

                    /* Outputs do not match! */
                    match = 0;
                    break;
                } else if (bytes_executed == 0) {
                    break;
                }
            }
            kill(child_pid, SIGKILL);
            break;

        case -1:
            /* Fatal */
            perror("Unable to fork");
            break;
    }

    if (!match)
        dprintf(STDERR_FILENO, "Mismatch detected near offset %*X (%d bytes chunk)!\n",
                total_bytes_executed-bytes_executed, bytes_executed);

    return match == 0;
}