scripts/insert-sys-cert.c

   1 /* Write the contents of the <certfile> into kernel symbol system_extra_cert
   2  *
   3  * Copyright (C) IBM Corporation, 2015
   4  *
   5  * Author: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>
   6  *
   7  * This software may be used and distributed according to the terms
   8  * of the GNU General Public License, incorporated herein by reference.
   9  *
  10  * Usage: insert-sys-cert [-s <System.map>] -b <vmlinux> -c <certfile>
  11  *                        [-s <System.map>] -z <bzImage> -c <certfile>
  12  */
  13
  14 #define _GNU_SOURCE
  15 #include <stdio.h>
  16 #include <ctype.h>
  17 #include <string.h>
  18 #include <limits.h>
  19 #include <stdbool.h>
  20 #include <errno.h>
  21 #include <stdlib.h>
  22 #include <stdarg.h>
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <sys/mman.h>
  26 #include <fcntl.h>
  27 #include <unistd.h>
  28 #include <elf.h>
  29
  30 #define CERT_SYM  "system_extra_cert"
  31 #define USED_SYM  "system_extra_cert_used"
  32 #define LSIZE_SYM "system_certificate_list_size"
  33
  34 #define info(format, args...) fprintf(stderr, "INFO:    " format, ## args)
  35 #define warn(format, args...) fprintf(stdout, "WARNING: " format, ## args)
  36 #define  err(format, args...) fprintf(stderr, "ERROR:   " format, ## args)
  37
  38 #if UINTPTR_MAX == 0xffffffff
  39 #define CURRENT_ELFCLASS ELFCLASS32
  40 #define Elf_Ehdr        Elf32_Ehdr
  41 #define Elf_Shdr        Elf32_Shdr
  42 #define Elf_Sym         Elf32_Sym
  43 #else
  44 #define CURRENT_ELFCLASS ELFCLASS64
  45 #define Elf_Ehdr        Elf64_Ehdr
  46 #define Elf_Shdr        Elf64_Shdr
  47 #define Elf_Sym         Elf64_Sym
  48 #endif
  49
  50 static unsigned char endianness(void)
  51 {
  52         uint16_t two_byte = 0x00FF;
  53         uint8_t low_address = *((uint8_t *)&two_byte);
  54
  55         if (low_address == 0)
  56                 return ELFDATA2MSB;
  57         else
  58                 return ELFDATA2LSB;
  59 }
  60
  61 struct sym {
  62         char *name;
  63         unsigned long address;
  64         unsigned long offset;
  65         void *content;
  66         int size;
  67 };
  68
  69 static unsigned long get_offset_from_address(Elf_Ehdr *hdr, unsigned long addr)
  70 {
  71         Elf_Shdr *x;
  72         unsigned int i, num_sections;
  73
  74         x = (void *)hdr + hdr->e_shoff;
  75         if (hdr->e_shnum == SHN_UNDEF)
  76                 num_sections = x[0].sh_size;
  77         else
  78                 num_sections = hdr->e_shnum;
  79
  80         for (i = 1; i < num_sections; i++) {
  81                 unsigned long start = x[i].sh_addr;
  82                 unsigned long end = start + x[i].sh_size;
  83                 unsigned long offset = x[i].sh_offset;
  84
  85                 if (addr >= start && addr <= end)
  86                         return addr - start + offset;
  87         }
  88         return 0;
  89 }
  90
  91
  92 #define LINE_SIZE 100
  93
  94 static void get_symbol_from_map(Elf_Ehdr *hdr, FILE *f, char *name,
  95                                 struct sym *s)
  96 {
  97         char l[LINE_SIZE];
  98         char *w, *p, *n;
  99
 100         s->size = 0;
 101         s->address = 0;
 102         s->offset = 0;
 103         if (fseek(f, 0, SEEK_SET) != 0) {
 104                 perror("File seek failed");
 105                 exit(EXIT_FAILURE);
 106         }
 107         while (fgets(l, LINE_SIZE, f)) {
 108                 p = strchr(l, '\n');
 109                 if (!p) {
 110                         err("Missing line ending.\n");
 111                         return;
 112                 }
 113                 n = strstr(l, name);
 114                 if (n)
 115                         break;
 116         }
 117         if (!n) {
 118                 err("Unable to find symbol: %s\n", name);
 119                 return;
 120         }
 121         w = strchr(l, ' ');
 122         if (!w)
 123                 return;
 124
 125         *w = '\0';
 126         s->address = strtoul(l, NULL, 16);
 127         if (s->address == 0)
 128                 return;
 129         s->offset = get_offset_from_address(hdr, s->address);
 130         s->name = name;
 131         s->content = (void *)hdr + s->offset;
 132 }
 133
 134 static Elf_Sym *find_elf_symbol(Elf_Ehdr *hdr, Elf_Shdr *symtab, char *name)
 135 {
 136         Elf_Sym *sym, *symtab_start;
 137         char *strtab, *symname;
 138         unsigned int link;
 139         Elf_Shdr *x;
 140         int i, n;
 141
 142         x = (void *)hdr + hdr->e_shoff;
 143         link = symtab->sh_link;
 144         symtab_start = (void *)hdr + symtab->sh_offset;
 145         n = symtab->sh_size / symtab->sh_entsize;
 146         strtab = (void *)hdr + x[link].sh_offset;
 147
 148         for (i = 0; i < n; i++) {
 149                 sym = &symtab_start[i];
 150                 symname = strtab + sym->st_name;
 151                 if (strcmp(symname, name) == 0)
 152                         return sym;
 153         }
 154         err("Unable to find symbol: %s\n", name);
 155         return NULL;
 156 }
 157
 158 static void get_symbol_from_table(Elf_Ehdr *hdr, Elf_Shdr *symtab,
 159                                   char *name, struct sym *s)
 160 {
 161         Elf_Shdr *sec;
 162         int secndx;
 163         Elf_Sym *elf_sym;
 164         Elf_Shdr *x;
 165
 166         x = (void *)hdr + hdr->e_shoff;
 167         s->size = 0;
 168         s->address = 0;
 169         s->offset = 0;
 170         elf_sym = find_elf_symbol(hdr, symtab, name);
 171         if (!elf_sym)
 172                 return;
 173         secndx = elf_sym->st_shndx;
 174         if (!secndx)
 175                 return;
 176         sec = &x[secndx];
 177         s->size = elf_sym->st_size;
 178         s->address = elf_sym->st_value;
 179         s->offset = s->address - sec->sh_addr
 180                                + sec->sh_offset;
 181         s->name = name;
 182         s->content = (void *)hdr + s->offset;
 183 }
 184
 185 static Elf_Shdr *get_symbol_table(Elf_Ehdr *hdr)
 186 {
 187         Elf_Shdr *x;
 188         unsigned int i, num_sections;
 189
 190         x = (void *)hdr + hdr->e_shoff;
 191         if (hdr->e_shnum == SHN_UNDEF)
 192                 num_sections = x[0].sh_size;
 193         else
 194                 num_sections = hdr->e_shnum;
 195
 196         for (i = 1; i < num_sections; i++)
 197                 if (x[i].sh_type == SHT_SYMTAB)
 198                         return &x[i];
 199         return NULL;
 200 }
 201
 202 static void *map_file(char *file_name, int *size)
 203 {
 204         struct stat st;
 205         void *map;
 206         int fd;
 207
 208         fd = open(file_name, O_RDWR);
 209         if (fd < 0) {
 210                 perror(file_name);
 211                 return NULL;
 212         }
 213         if (fstat(fd, &st)) {
 214                 perror("Could not determine file size");
 215                 close(fd);
 216                 return NULL;
 217         }
 218         *size = st.st_size;
 219         map = mmap(NULL, *size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 220         if (map == MAP_FAILED) {
 221                 perror("Mapping to memory failed");
 222                 close(fd);
 223                 return NULL;
 224         }
 225         close(fd);
 226         return map;
 227 }
 228
 229 static char *read_file(char *file_name, int *size)
 230 {
 231         struct stat st;
 232         char *buf;
 233         int fd;
 234
 235         fd = open(file_name, O_RDONLY);
 236         if (fd < 0) {
 237                 perror(file_name);
 238                 return NULL;
 239         }
 240         if (fstat(fd, &st)) {
 241                 perror("Could not determine file size");
 242                 close(fd);
 243                 return NULL;
 244         }
 245         *size = st.st_size;
 246         buf = malloc(*size);
 247         if (!buf) {
 248                 perror("Allocating memory failed");
 249                 close(fd);
 250                 return NULL;
 251         }
 252         if (read(fd, buf, *size) != *size) {
 253                 perror("File read failed");
 254                 close(fd);
 255                 return NULL;
 256         }
 257         close(fd);
 258         return buf;
 259 }
 260
 261 static void get_payload_info(char *bzimage, int *offset, int *size)
 262 {
 263         unsigned int system_offset;
 264         unsigned char setup_sectors;
 265
 266         setup_sectors = bzimage[0x1f1] + 1;
 267         system_offset = setup_sectors * 512;
 268         *offset = system_offset + *((int*)&bzimage[0x248]);
 269         *size = *((int*)&bzimage[0x24c]);
 270 }
 271
 272 static void update_payload_info(char* bzimage, int new_size)
 273 {
 274         int offset, size;
 275         get_payload_info(bzimage, &offset, &size);
 276         *((int*)&bzimage[0x24c]) = new_size;
 277         if (new_size < size)
 278                 memset(bzimage + offset + new_size, 0, size - new_size);
 279 }
 280
 281 struct zipper {
 282         unsigned char pattern[10];
 283         int length;
 284         char *command;
 285         char *compress;
 286 };
 287
 288 struct zipper zippers[] = {
 289         {{0x7F,'E','L','F'}, 4, "cat", "cat"},
 290         {{0x1F,0x8B}, 2, "gunzip", "gzip -n -f -9"},
 291         {{0xFD,'7','z','X','Z',0}, 6, "unxz", "xz"},
 292         {{'B','Z','h'},3, "bunzip2", "bzip2 -9"},
 293         {{0xFF,'L','Z','M','A',0}, 6, "unlzma", "lzma -9"},
 294         {{0xD3,'L','Z','O',0,'\r','\n',0x20,'\n'}, 9, "lzop -d", "lzop -9"}
 295 };
 296
 297 static struct zipper* get_zipper(char *p) {
 298         int i;
 299         for (i = 0; i < sizeof(zippers)/sizeof(struct zipper); i++) {
 300                 if (memcmp(p, zippers[i].pattern, zippers[i].length) == 0)
 301                         return &zippers[i];
 302         }
 303         return NULL;
 304 }
 305
 306 /*
 307  * This only works for x86 bzImage
 308  */
 309 static void extract_vmlinux(char *bzimage, int bzimage_size,
 310                         char **file, struct zipper **zipper)
 311 {
 312         int r;
 313         char src[15] = "vmlinux-XXXXXX";
 314         char dest[15] = "vmlinux-XXXXXX";
 315         char cmd[100];
 316         int src_fd, dest_fd;
 317         int offset, size;
 318         struct zipper *z;
 319
 320         /* TODO: verify that bzImage is supported */
 321
 322         get_payload_info(bzimage, &offset, &size);
 323         z = get_zipper(bzimage + offset);
 324         if (z == NULL) {
 325                 err("Unable to determine the compression of vmlinux\n");
 326                 return;
 327         }
 328
 329         src_fd = mkstemp(src);
 330         if (src_fd == -1) {
 331                 perror("Could not create temp file");
 332                 return;
 333         }
 334
 335         r = write(src_fd, bzimage + offset, size);
 336         if (r != size) {
 337                 perror("Could not write vmlinux");
 338                 return;
 339         }
 340         dest_fd = mkstemp(dest);
 341         if (dest_fd == -1) {
 342                 perror("Could not create temp file");
 343                 return;
 344         }
 345
 346         snprintf(cmd, sizeof(cmd), "%s <%s >%s", z->command, src, dest);
 347         info("Executing: %s\n", cmd);
 348         r = system(cmd);
 349         if (r!=0)
 350                 warn("Possible errors when extracting\n");
 351
 352         r = remove(src);
 353         if (r!=0)
 354                 perror(src);
 355
 356         *file = strdup(dest);
 357         *zipper = z;
 358 }
 359
 360 static void repack_image(char *bzimage, int bzimage_size,
 361                         char* vmlinux_file, struct zipper *z)
 362 {
 363         char tmp[15] = "vmlinux-XXXXXX";
 364         char cmd[100];
 365         int fd;
 366         struct stat st;
 367         int new_size;
 368         int r;
 369         int offset, size;
 370
 371         get_payload_info(bzimage, &offset, &size);
 372
 373         fd = mkstemp(tmp);
 374         if (fd == -1) {
 375                 perror("Could not create temp file");
 376                 return;
 377         }
 378         snprintf(cmd, sizeof(cmd), "%s <%s >%s",
 379                         z->compress, vmlinux_file, tmp);
 380
 381         info("Executing: %s\n", cmd);
 382         r = system(cmd);
 383         if (r!=0)
 384                 warn("Possible errors when compressing\n");
 385
 386         r = remove(vmlinux_file);
 387         if (r!=0)
 388                 perror(vmlinux_file);
 389
 390         if (fstat(fd, &st)) {
 391                 perror("Could not determine file size");
 392                 close(fd);
 393
 394         }
 395         new_size = st.st_size;
 396         if (new_size > size) {
 397                 err("Increase in compressed size is not supported.\n");
 398                 err("Old size was %d, new size is %d\n", size, new_size);
 399                 exit(EXIT_FAILURE);
 400         }
 401
 402         r = read(fd, bzimage + offset, new_size);
 403         if (r != new_size)
 404                 perror(tmp);
 405
 406         r = remove(tmp);
 407         if (r!=0)
 408                 perror(tmp);
 409
 410         /* x86 specific patching of bzimage */
 411         update_payload_info(bzimage, new_size);
 412
 413         /* TODO: update CRC */
 414
 415 }
 416
 417 static void fill_random(unsigned char *p, int n) {
 418         srand(0);
 419         int i;
 420         for (i = 0; i < n; i++)
 421                 p[i] = rand();
 422 }
 423
 424 static void print_sym(Elf_Ehdr *hdr, struct sym *s)
 425 {
 426         info("sym:    %s\n", s->name);
 427         info("addr:   0x%lx\n", s->address);
 428         info("size:   %d\n", s->size);
 429         info("offset: 0x%lx\n", (unsigned long)s->offset);
 430 }
 431
 432 static void print_usage(char *e)
 433 {
 434         printf("Usage: %s [-s <System.map>] -b <vmlinux> -c <certfile>\n", e);
 435         printf("       %s [-s <System.map>] -z <bzImage> -c <certfile>\n", e);
 436 }
 437
 438 int main(int argc, char **argv)
 439 {
 440         char *system_map_file = NULL;
 441         char *vmlinux_file = NULL;
 442         char *bzimage_file = NULL;
 443         char *cert_file = NULL;
 444         int vmlinux_size;
 445         int bzimage_size;
 446         int cert_size;
 447         Elf_Ehdr *hdr;
 448         char *cert;
 449         char *bzimage = NULL;
 450         struct zipper *z = NULL;
 451         FILE *system_map;
 452         unsigned long *lsize;
 453         int *used;
 454         int opt;
 455         Elf_Shdr *symtab = NULL;
 456         struct sym cert_sym, lsize_sym, used_sym;
 457
 458         while ((opt = getopt(argc, argv, "b:z:c:s:")) != -1) {
 459                 switch (opt) {
 460                 case 's':
 461                         system_map_file = optarg;
 462                         break;
 463                 case 'b':
 464                         vmlinux_file = optarg;
 465                         break;
 466                 case 'z':
 467                         bzimage_file = optarg;
 468                         break;
 469                 case 'c':
 470                         cert_file = optarg;
 471                         break;
 472                 default:
 473                         break;
 474                 }
 475         }
 476
 477         if (!cert_file ||
 478         (!vmlinux_file && !bzimage_file) ||
 479         (vmlinux_file && bzimage_file)) {
 480                 print_usage(argv[0]);
 481                 exit(EXIT_FAILURE);
 482         }
 483
 484         cert = read_file(cert_file, &cert_size);
 485         if (!cert)
 486                 exit(EXIT_FAILURE);
 487
 488         if (bzimage_file) {
 489                 bzimage = map_file(bzimage_file, &bzimage_size);
 490                 if (!bzimage)
 491                         exit(EXIT_FAILURE);
 492
 493                 extract_vmlinux(bzimage, bzimage_size, &vmlinux_file, &z);
 494                 if (!vmlinux_file)
 495                         exit(EXIT_FAILURE);
 496         }
 497
 498         hdr = map_file(vmlinux_file, &vmlinux_size);
 499         if (!hdr)
 500                 exit(EXIT_FAILURE);
 501
 502         if (vmlinux_size < sizeof(*hdr)) {
 503                 err("Invalid ELF file.\n");
 504                 exit(EXIT_FAILURE);
 505         }
 506
 507         if ((hdr->e_ident[EI_MAG0] != ELFMAG0) ||
 508             (hdr->e_ident[EI_MAG1] != ELFMAG1) ||
 509             (hdr->e_ident[EI_MAG2] != ELFMAG2) ||
 510             (hdr->e_ident[EI_MAG3] != ELFMAG3)) {
 511                 err("Invalid ELF magic.\n");
 512                 exit(EXIT_FAILURE);
 513         }
 514
 515         if (hdr->e_ident[EI_CLASS] != CURRENT_ELFCLASS) {
 516                 err("ELF class mismatch.\n");
 517                 exit(EXIT_FAILURE);
 518         }
 519
 520         if (hdr->e_ident[EI_DATA] != endianness()) {
 521                 err("ELF endian mismatch.\n");
 522                 exit(EXIT_FAILURE);
 523         }
 524
 525         if (hdr->e_shoff > vmlinux_size) {
 526                 err("Could not find section header.\n");
 527                 exit(EXIT_FAILURE);
 528         }
 529
 530         symtab = get_symbol_table(hdr);
 531         if (!symtab) {
 532                 warn("Could not find the symbol table.\n");
 533                 if (!system_map_file) {
 534                         err("Please provide a System.map file.\n");
 535                         print_usage(argv[0]);
 536                         exit(EXIT_FAILURE);
 537                 }
 538
 539                 system_map = fopen(system_map_file, "r");
 540                 if (!system_map) {
 541                         perror(system_map_file);
 542                         exit(EXIT_FAILURE);
 543                 }
 544                 get_symbol_from_map(hdr, system_map, CERT_SYM, &cert_sym);
 545                 get_symbol_from_map(hdr, system_map, USED_SYM, &used_sym);
 546                 get_symbol_from_map(hdr, system_map, LSIZE_SYM, &lsize_sym);
 547                 cert_sym.size = used_sym.address - cert_sym.address;
 548         } else {
 549                 info("Symbol table found.\n");
 550                 if (system_map_file)
 551                         warn("System.map is ignored.\n");
 552                 get_symbol_from_table(hdr, symtab, CERT_SYM, &cert_sym);
 553                 get_symbol_from_table(hdr, symtab, USED_SYM, &used_sym);
 554                 get_symbol_from_table(hdr, symtab, LSIZE_SYM, &lsize_sym);
 555         }
 556
 557         if (!cert_sym.offset || !lsize_sym.offset || !used_sym.offset)
 558                 exit(EXIT_FAILURE);
 559
 560         print_sym(hdr, &cert_sym);
 561         print_sym(hdr, &used_sym);
 562         print_sym(hdr, &lsize_sym);
 563
 564         lsize = (unsigned long *)lsize_sym.content;
 565         used = (int *)used_sym.content;
 566
 567         if (cert_sym.size < cert_size) {
 568                 err("Certificate is larger than the reserved area!\n");
 569                 exit(EXIT_FAILURE);
 570         }
 571
 572         /* If the existing cert is the same, don't overwrite */
 573         if (cert_size > 0 && cert_size == *used &&
 574             strncmp(cert_sym.content, cert, cert_size) == 0) {
 575                 warn("Certificate was already inserted.\n");
 576                 exit(EXIT_SUCCESS);
 577         }
 578
 579         if (*used > 0)
 580                 warn("Replacing previously inserted certificate.\n");
 581
 582         memcpy(cert_sym.content, cert, cert_size);
 583
 584         if (cert_size < cert_sym.size)
 585                 /* This makes the reserved space incompressable */
 586                 fill_random(cert_sym.content + cert_size,
 587                                 cert_sym.size - cert_size);
 588
 589         *lsize = *lsize + cert_size - *used;
 590         *used = cert_size;
 591         info("Inserted the contents of %s into %lx.\n", cert_file,
 592                                                 cert_sym.address);
 593         info("Used %d bytes out of %d bytes reserved.\n", *used,
 594                                                  cert_sym.size);
 595
 596         if (munmap(hdr, vmlinux_size) == -1) {
 597                 perror(vmlinux_file);
 598                 exit(EXIT_FAILURE);
 599         }
 600
 601         if (bzimage) {
 602                 repack_image(bzimage, bzimage_size, vmlinux_file, z);
 603         }
 604
 605         exit(EXIT_SUCCESS);
 606 }