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lsmbr.c
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lsmbr.c
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/*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "pt-mbr-partnames.h"
#define VERSION 1
#define SUBVERSION 0
#define SECTOR_SIZE 512
#define RESET "\033[0m"
#define BLACK "\033[30m" /* Black */
#define RED "\033[31m" /* Red */
#define GREEN "\033[32m" /* Green */
#define YELLOW "\033[33m" /* Yellow */
#define BLUE "\033[34m" /* Blue */
#define MAGENTA "\033[35m" /* Magenta */
#define CYAN "\033[36m" /* Cyan */
#define WHITE "\033[37m" /* White */
#define BOLDBLACK "\033[1m\033[30m" /* Bold Black */
#define BOLDRED "\033[1m\033[31m" /* Bold Red */
#define BOLDGREEN "\033[1m\033[32m" /* Bold Green */
#define BOLDYELLOW "\033[1m\033[33m" /* Bold Yellow */
#define BOLDBLUE "\033[1m\033[34m" /* Bold Blue */
#define BOLDMAGENTA "\033[1m\033[35m" /* Bold Magenta */
#define BOLDCYAN "\033[1m\033[36m" /* Bold Cyan */
#define BOLDWHITE "\033[1m\033[37m" /* Bold White */
int is_gpt = 0;
struct _partition {
uint8_t status;
uint8_t chs_start[3];
uint8_t part_type;
uint8_t chs_end[3];
uint32_t lba_start;
uint32_t sectors;
};
void show_bytes(unsigned char* mbr, int length) {
for (size_t i = 0; i < length; i++) {
printf("%.2x ", mbr[i]);
if ((i + 1) % 16 == 0)
printf("\n");
}
printf("\n");
}
void check_file_validity(char* fd) {
if (!access(fd, F_OK) == 0) {
printf("File doesn't exist\n");
exit(EXIT_FAILURE);
}
if (!access(fd, R_OK) == 0) {
printf("No read permissions\n");
exit(EXIT_FAILURE);
}
}
void mbr_bootstrap(unsigned char* mbr, int length) {
printf("%sBootstrap code area%s", MAGENTA, RESET);
for (size_t i = 0; i < length; i++) {
if (mbr[i] != 0) {
printf("%s - disklabel type: DOS (or GPT for legacy BIOS)%s\n", GREEN, RESET);
break;
}
if (i == length - 1) {
printf("%s - disklabel type: GPT%s\n", GREEN, RESET);
is_gpt = 1;
}
}
show_bytes(mbr, length);
if (!is_gpt) {
printf("\n%sEnter 'y' to see raw binary: %s", GREEN, RESET);
char raw;
scanf("%c", &raw);
if (raw == 'y') {
write(STDOUT_FILENO, mbr, length);
printf("\n");
}
}
}
/* chs[3] in this order: head (8 bits), sector (6 bits), cylinder (10 bits) */
void show_chs_coords(uint8_t* chs, char* id) {
uint8_t sector = chs[1] & 0b00111111;
uint16_t cylinder = ((chs[1] & 0b11000000) << 2) | chs[2];
printf("%s head, sector, cylinder coordinates: ", id);
printf("%s%.2x, %.2x, %.2x%s\n", RED, chs[0], sector, cylinder, RESET);
}
void show_type(uint8_t id) {
char* type = "";
for (size_t i = 0; pt_types[i].type != 0; i++)
if (pt_types[i].id == id)
type = pt_types[i].type;
printf("Id: %s%x%s, type: %s\n", RED, id, RESET, type);
}
void partition_records(unsigned char* mbr, int part_length, int part_num) {
for (size_t i = 0; i < part_num; i++) {
struct _partition* p = (void *) (mbr + i * part_length);
printf("\n%s<Partition %ld>%s", BOLDYELLOW, i, RESET);
/* Sector coordinate can't be 0 */
if ((p->chs_start[1] & 0b00111111) == 0) {
printf(" - doesn't exist\n");
continue;
}
char *bootable = p->status == 0 ? " not" : "";
printf("\nBoot indicator: %s%.2x%s -%s bootable\n", RED, p->status, RESET, bootable);
show_chs_coords(p->chs_start, "Starting");
show_type(p->part_type);
show_chs_coords(p->chs_end, "Ending");
printf("Logical block address of first absolute sector in the partition: %s%.2x%s\n", RED, p->lba_start, RESET);
printf("Number of sectors in partition: %s%.2x%s\n", RED, p->sectors, RESET);
}
printf("\n");
}
void analyze(unsigned char* mbr) {
unsigned char magic_num[2];
magic_num[0] = 0x55; magic_num[1] = 0xaa;
if (strncmp((const char*) (mbr + 510), (const char*) magic_num, 2) != 0) {
printf("Not a MBR\n");
exit(EXIT_FAILURE);
}
mbr_bootstrap(mbr, 440);
printf("\n%sDisk identifier: %s", MAGENTA, RESET);
show_bytes((mbr+440), 4);
printf("%sUnknown: %s", MAGENTA, RESET);
show_bytes((mbr+444), 2);
partition_records((mbr+446), 16, 4);
printf("%sSignature: %s", MAGENTA, RESET);
show_bytes((mbr+510), 2);
}
int main(int argc, char *argv[]) {
unsigned char mbr[SECTOR_SIZE];
int fd;
if(argc == 2) {
check_file_validity(argv[1]);
fd = open(argv[1], O_RDONLY);
lseek(fd, 0, SEEK_SET); /* Offset 0 */
read(fd, mbr, SECTOR_SIZE);
printf("%sMBR analyzer, v%d.%d:%s\n", RED, VERSION, SUBVERSION, RESET);
analyze(mbr);
printf("\n%sEnter 'y' to see full MBR sector: %s", GREEN, RESET);
char full;
scanf(" %c", &full);
if (full == 'y')
show_bytes(mbr, SECTOR_SIZE);
} else {
printf("Incorrect usage: lsmbr <disk>\n");
}
}