name : insert-sys-cert.c /* Write the contents of the <certfile> into kernel symbol system_extra_cert * * Copyright (C) IBM Corporation, 2015 * * Author: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com> * * This software may be used and distributed according to the terms * of the GNU General Public License, incorporated herein by reference. * * Usage: insert-sys-cert [-s <System.map>] -b <vmlinux> -c <certfile> * [-s <System.map>] -z <bzImage> -c <certfile> */ #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 #else #define CURRENT_ELFCLASS ELFCLASS64 #define Elf_Ehdr Elf64_Ehdr #define Elf_Shdr Elf64_Shdr #define Elf_Sym Elf64_Sym #endif 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 { char *name; unsigned long address; unsigned long offset; void *content; int size; }; 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 get_payload_info(char *bzimage, int *offset, int *size) { unsigned int system_offset; unsigned char setup_sectors; setup_sectors = bzimage[0x1f1] + 1; system_offset = setup_sectors * 512; *offset = system_offset + *((int*)&bzimage[0x248]); *size = *((int*)&bzimage[0x24c]); } static void update_payload_info(char* bzimage, int new_size) { int offset, size; get_payload_info(bzimage, &offset, &size); *((int*)&bzimage[0x24c]) = new_size; if (new_size < size) memset(bzimage + offset + new_size, 0, size - new_size); } struct zipper { unsigned char pattern[10]; int length; char *command; char *compress; }; struct zipper zippers[] = { {{0x7F,'E','L','F'}, 4, "cat", "cat"}, {{0x1F,0x8B}, 2, "gunzip", "gzip -n -f -9"}, {{0xFD,'7','z','X','Z',0}, 6, "unxz", "xz"}, {{'B','Z','h'},3, "bunzip2", "bzip2 -9"}, {{0xFF,'L','Z','M','A',0}, 6, "unlzma", "lzma -9"}, {{0xD3,'L','Z','O',0,'\r','\n',0x20,'\n'}, 9, "lzop -d", "lzop -9"} }; static struct zipper* get_zipper(char *p) { int i; for (i = 0; i < sizeof(zippers)/sizeof(struct zipper); i++) { if (memcmp(p, zippers[i].pattern, zippers[i].length) == 0) return &zippers[i]; } return NULL; } /* * This only works for x86 bzImage */ static void extract_vmlinux(char *bzimage, int bzimage_size, char **file, struct zipper **zipper) { int r; char src[15] = "vmlinux-XXXXXX"; char dest[15] = "vmlinux-XXXXXX"; char cmd[100]; int src_fd, dest_fd; int offset, size; struct zipper *z; /* TODO: verify that bzImage is supported */ get_payload_info(bzimage, &offset, &size); z = get_zipper(bzimage + offset); if (z == NULL) { err("Unable to determine the compression of vmlinux\n"); return; } src_fd = mkstemp(src); if (src_fd == -1) { perror("Could not create temp file"); return; } r = write(src_fd, bzimage + offset, size); if (r != size) { perror("Could not write vmlinux"); return; } dest_fd = mkstemp(dest); if (dest_fd == -1) { perror("Could not create temp file"); return; } snprintf(cmd, sizeof(cmd), "%s <%s >%s", z->command, src, dest); info("Executing: %s\n", cmd); r = system(cmd); if (r!=0) warn("Possible errors when extracting\n"); r = remove(src); if (r!=0) perror(src); *file = strdup(dest); *zipper = z; } static void repack_image(char *bzimage, int bzimage_size, char* vmlinux_file, struct zipper *z) { char tmp[15] = "vmlinux-XXXXXX"; char cmd[100]; int fd; struct stat st; int new_size; int r; int offset, size; get_payload_info(bzimage, &offset, &size); fd = mkstemp(tmp); if (fd == -1) { perror("Could not create temp file"); return; } snprintf(cmd, sizeof(cmd), "%s <%s >%s", z->compress, vmlinux_file, tmp); info("Executing: %s\n", cmd); r = system(cmd); if (r!=0) warn("Possible errors when compressing\n"); r = remove(vmlinux_file); if (r!=0) perror(vmlinux_file); if (fstat(fd, &st)) { perror("Could not determine file size"); close(fd); } new_size = st.st_size; if (new_size > size) { err("Increase in compressed size is not supported.\n"); err("Old size was %d, new size is %d\n", size, new_size); exit(EXIT_FAILURE); } r = read(fd, bzimage + offset, new_size); if (r != new_size) perror(tmp); r = remove(tmp); if (r!=0) perror(tmp); /* x86 specific patching of bzimage */ update_payload_info(bzimage, new_size); /* TODO: update CRC */ } static void fill_random(unsigned char *p, int n) { srand(0); int i; for (i = 0; i < n; i++) p[i] = rand(); } 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); printf(" %s [-s <System.map>] -z <bzImage> -c <certfile>\n", e); } int main(int argc, char **argv) { char *system_map_file = NULL; char *vmlinux_file = NULL; char *bzimage_file = NULL; char *cert_file = NULL; int vmlinux_size; int bzimage_size; int cert_size; Elf_Ehdr *hdr; char *cert; char *bzimage = NULL; struct zipper *z = NULL; 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:z:c:s:")) != -1) { switch (opt) { case 's': system_map_file = optarg; break; case 'b': vmlinux_file = optarg; break; case 'z': bzimage_file = optarg; break; case 'c': cert_file = optarg; break; default: break; } } if (!cert_file || (!vmlinux_file && !bzimage_file) || (vmlinux_file && bzimage_file)) { print_usage(argv[0]); exit(EXIT_FAILURE); } cert = read_file(cert_file, &cert_size); if (!cert) exit(EXIT_FAILURE); if (bzimage_file) { bzimage = map_file(bzimage_file, &bzimage_size); if (!bzimage) exit(EXIT_FAILURE); extract_vmlinux(bzimage, bzimage_size, &vmlinux_file, &z); if (!vmlinux_file) 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 > 0 && 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) /* This makes the reserved space incompressable */ fill_random(cert_sym.content + cert_size, 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); if (munmap(hdr, vmlinux_size) == -1) { perror(vmlinux_file); exit(EXIT_FAILURE); } if (bzimage) { repack_image(bzimage, bzimage_size, vmlinux_file, z); } exit(EXIT_SUCCESS); }