#define _GNU_SOURCE

#include <stdio.h>

#include <ctype.h>

#include <string.h>

#include <limits.h>

#include <stdbool.h>

#include <errno.h>

#include <stdlib.h>

#include <stdarg.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/mman.h>

#include <fcntl.h>

#include <unistd.h>

#include <elf.h>

#define CERT_SYM "system_extra_cert"

#define USED_SYM "system_extra_cert_used"

#define LSIZE_SYM "system_certificate_list_size"

#define info(format, args...) fprintf(stderr, "INFO: " format, ## args)

#define warn(format, args...) fprintf(stdout, "WARNING: " format, ## args)

#define err(format, args...) fprintf(stderr, "ERROR: " format, ## args)

#if UINTPTR_MAX == 0xffffffff

#define CURRENT_ELFCLASS ELFCLASS32

#define Elf_Ehdr Elf32_Ehdr

#define Elf_Shdr Elf32_Shdr

#define Elf_Sym Elf32_Sym

#define CURRENT_ELFCLASS ELFCLASS64

#define Elf_Ehdr Elf64_Ehdr

#define Elf_Shdr Elf64_Shdr

#define Elf_Sym Elf64_Sym

static unsigned char endianness(void)

{

uint16_t two_byte = 0x00FF;

uint8_t low_address = *((uint8_t *)&two_byte);

if (low_address == 0)

return ELFDATA2MSB;

else

return ELFDATA2LSB;

}

struct sym {

};

static unsigned long get_offset_from_address(Elf_Ehdr *hdr, unsigned long addr)

{

Elf_Shdr *x;

unsigned int i, num_sections;

x = (void *)hdr + hdr->e_shoff;

if (hdr->e_shnum == SHN_UNDEF)

num_sections = x[0].sh_size;

else

num_sections = hdr->e_shnum;

for (i = 1; i < num_sections; i++) {

unsigned long start = x[i].sh_addr;

unsigned long end = start + x[i].sh_size;

unsigned long offset = x[i].sh_offset;

if (addr >= start && addr <= end)

return addr - start + offset;

}

return 0;

}

#define LINE_SIZE 100

static void get_symbol_from_map(Elf_Ehdr *hdr, FILE *f, char *name,

struct sym *s)

{

char l[LINE_SIZE];

char *w, *p, *n;

s->size = 0;

s->address = 0;

s->offset = 0;

if (fseek(f, 0, SEEK_SET) != 0) {

perror("File seek failed");

exit(EXIT_FAILURE);

}

while (fgets(l, LINE_SIZE, f)) {

p = strchr(l, '\n');

if (!p) {

err("Missing line ending.\n");

return;

}

n = strstr(l, name);

if (n)

break;

}

if (!n) {

err("Unable to find symbol: %s\n", name);

return;

}

w = strchr(l, ' ');

if (!w)

return;

*w = '\0';

s->address = strtoul(l, NULL, 16);

if (s->address == 0)

return;

s->offset = get_offset_from_address(hdr, s->address);

s->name = name;

s->content = (void *)hdr + s->offset;

}

static Elf_Sym *find_elf_symbol(Elf_Ehdr *hdr, Elf_Shdr *symtab, char *name)

{

Elf_Sym *sym, *symtab_start;

char *strtab, *symname;

unsigned int link;

Elf_Shdr *x;

int i, n;

x = (void *)hdr + hdr->e_shoff;

link = symtab->sh_link;

symtab_start = (void *)hdr + symtab->sh_offset;

n = symtab->sh_size / symtab->sh_entsize;

strtab = (void *)hdr + x[link].sh_offset;

for (i = 0; i < n; i++) {

sym = &symtab_start[i];

symname = strtab + sym->st_name;

if (strcmp(symname, name) == 0)

return sym;

}

err("Unable to find symbol: %s\n", name);

return NULL;

}

static void get_symbol_from_table(Elf_Ehdr *hdr, Elf_Shdr *symtab,

char *name, struct sym *s)

{

Elf_Shdr *sec;

int secndx;

Elf_Sym *elf_sym;

Elf_Shdr *x;

x = (void *)hdr + hdr->e_shoff;

s->size = 0;

s->address = 0;

s->offset = 0;

elf_sym = find_elf_symbol(hdr, symtab, name);

if (!elf_sym)

return;

secndx = elf_sym->st_shndx;

if (!secndx)

return;

sec = &x[secndx];

s->size = elf_sym->st_size;

s->address = elf_sym->st_value;

s->offset = s->address - sec->sh_addr

+ sec->sh_offset;

s->name = name;

s->content = (void *)hdr + s->offset;

}

static Elf_Shdr *get_symbol_table(Elf_Ehdr *hdr)

{

Elf_Shdr *x;

unsigned int i, num_sections;

x = (void *)hdr + hdr->e_shoff;

if (hdr->e_shnum == SHN_UNDEF)

num_sections = x[0].sh_size;

else

num_sections = hdr->e_shnum;

for (i = 1; i < num_sections; i++)

if (x[i].sh_type == SHT_SYMTAB)

return &x[i];

return NULL;

}

static void *map_file(char *file_name, int *size)

{

struct stat st;

void *map;

int fd;

fd = open(file_name, O_RDWR);

if (fd < 0) {

perror(file_name);

return NULL;

}

if (fstat(fd, &st)) {

perror("Could not determine file size");

close(fd);

return NULL;

}

*size = st.st_size;

map = mmap(NULL, *size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

if (map == MAP_FAILED) {

perror("Mapping to memory failed");

close(fd);

return NULL;

}

close(fd);

return map;

}

static char *read_file(char *file_name, int *size)

{

struct stat st;

char *buf;

int fd;

fd = open(file_name, O_RDONLY);

if (fd < 0) {

perror(file_name);

return NULL;

}

if (fstat(fd, &st)) {

perror("Could not determine file size");

close(fd);

return NULL;

}

*size = st.st_size;

buf = malloc(*size);

if (!buf) {

perror("Allocating memory failed");

close(fd);

return NULL;

}

if (read(fd, buf, *size) != *size) {

perror("File read failed");

close(fd);

return NULL;

}

close(fd);

return buf;

}

static void print_sym(Elf_Ehdr *hdr, struct sym *s)

{

info("sym: %s\n", s->name);

info("addr: 0x%lx\n", s->address);

info("size: %d\n", s->size);

info("offset: 0x%lx\n", (unsigned long)s->offset);

}

static void print_usage(char *e)

{

printf("Usage %s [-s <System.map>] -b <vmlinux> -c <certfile>\n", e);

}

int main(int argc, char **argv)

{

char *system_map_file = NULL;

char *vmlinux_file = NULL;

char *cert_file = NULL;

int vmlinux_size;

int cert_size;

Elf_Ehdr *hdr;

char *cert;

FILE *system_map;

unsigned long *lsize;

int *used;

int opt;

Elf_Shdr *symtab = NULL;

struct sym cert_sym, lsize_sym, used_sym;

while ((opt = getopt(argc, argv, "b:c:s:")) != -1) {

switch (opt) {

case 's':

system_map_file = optarg;

break;

case 'b':

vmlinux_file = optarg;

break;

case 'c':

cert_file = optarg;

break;

default:

break;

}

}

if (!vmlinux_file || !cert_file) {

print_usage(argv[0]);

exit(EXIT_FAILURE);

}

cert = read_file(cert_file, &cert_size);

if (!cert)

exit(EXIT_FAILURE);

hdr = map_file(vmlinux_file, &vmlinux_size);

if (!hdr)

exit(EXIT_FAILURE);

if (vmlinux_size < sizeof(*hdr)) {

err("Invalid ELF file.\n");

exit(EXIT_FAILURE);

}

if ((hdr->e_ident[EI_MAG0] != ELFMAG0) ||

(hdr->e_ident[EI_MAG1] != ELFMAG1) ||

(hdr->e_ident[EI_MAG2] != ELFMAG2) ||

(hdr->e_ident[EI_MAG3] != ELFMAG3)) {

err("Invalid ELF magic.\n");

exit(EXIT_FAILURE);

}

if (hdr->e_ident[EI_CLASS] != CURRENT_ELFCLASS) {

err("ELF class mismatch.\n");

exit(EXIT_FAILURE);

}

if (hdr->e_ident[EI_DATA] != endianness()) {

err("ELF endian mismatch.\n");

exit(EXIT_FAILURE);

}

if (hdr->e_shoff > vmlinux_size) {

err("Could not find section header.\n");

exit(EXIT_FAILURE);

}

symtab = get_symbol_table(hdr);

if (!symtab) {

warn("Could not find the symbol table.\n");

if (!system_map_file) {

err("Please provide a System.map file.\n");

print_usage(argv[0]);

exit(EXIT_FAILURE);

}

system_map = fopen(system_map_file, "r");

if (!system_map) {

perror(system_map_file);

exit(EXIT_FAILURE);

}

get_symbol_from_map(hdr, system_map, CERT_SYM, &cert_sym);

get_symbol_from_map(hdr, system_map, USED_SYM, &used_sym);

get_symbol_from_map(hdr, system_map, LSIZE_SYM, &lsize_sym);

cert_sym.size = used_sym.address - cert_sym.address;

} else {

info("Symbol table found.\n");

if (system_map_file)

warn("System.map is ignored.\n");

get_symbol_from_table(hdr, symtab, CERT_SYM, &cert_sym);

get_symbol_from_table(hdr, symtab, USED_SYM, &used_sym);

get_symbol_from_table(hdr, symtab, LSIZE_SYM, &lsize_sym);

}

if (!cert_sym.offset || !lsize_sym.offset || !used_sym.offset)

exit(EXIT_FAILURE);

print_sym(hdr, &cert_sym);

print_sym(hdr, &used_sym);

print_sym(hdr, &lsize_sym);

lsize = (unsigned long *)lsize_sym.content;

used = (int *)used_sym.content;

if (cert_sym.size < cert_size) {

err("Certificate is larger than the reserved area!\n");

exit(EXIT_FAILURE);

}

/* If the existing cert is the same, don't overwrite */

if (cert_size == *used &&

strncmp(cert_sym.content, cert, cert_size) == 0) {

warn("Certificate was already inserted.\n");

exit(EXIT_SUCCESS);

}

if (*used > 0)

warn("Replacing previously inserted certificate.\n");

memcpy(cert_sym.content, cert, cert_size);

if (cert_size < cert_sym.size)

memset(cert_sym.content + cert_size,

0, cert_sym.size - cert_size);

*lsize = *lsize + cert_size - *used;

*used = cert_size;

info("Inserted the contents of %s into %lx.\n", cert_file,

cert_sym.address);

info("Used %d bytes out of %d bytes reserved.\n", *used,

cert_sym.size);

exit(EXIT_SUCCESS);

}