KEYS: Reserve an extra certificate symbol for inserting without recompiling
Place a system_extra_cert buffer of configurable size, right after the
system_certificate_list, so that inserted keys can be readily processed by
the existing mechanism. Added script takes a key file and a kernel image
and inserts its contents to the reserved area. The
system_certificate_list_size is also adjusted accordingly.
Call the script as:
scripts/insert-sys-cert -b <vmlinux> -c <certfile>
If vmlinux has no symbol table, supply System.map file with -s flag.
Subsequent runs replace the previously inserted key, instead of appending
the new one.
Signed-off-by: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
diff --git a/certs/Kconfig b/certs/Kconfig
index b030b9c..f0f8a44 100644
--- a/certs/Kconfig
+++ b/certs/Kconfig
@@ -39,4 +39,20 @@
form of DER-encoded *.x509 files in the top-level build directory,
those are no longer used. You will need to set this option instead.
+config SYSTEM_EXTRA_CERTIFICATE
+ bool "Reserve area for inserting a certificate without recompiling"
+ depends on SYSTEM_TRUSTED_KEYRING
+ help
+ If set, space for an extra certificate will be reserved in the kernel
+ image. This allows introducing a trusted certificate to the default
+ system keyring without recompiling the kernel.
+
+config SYSTEM_EXTRA_CERTIFICATE_SIZE
+ int "Number of bytes to reserve for the extra certificate"
+ depends on SYSTEM_EXTRA_CERTIFICATE
+ default 4096
+ help
+ This is the number of bytes reserved in the kernel image for a
+ certificate to be inserted.
+
endmenu
diff --git a/certs/system_certificates.S b/certs/system_certificates.S
index 9216e8c..f82e1b2 100644
--- a/certs/system_certificates.S
+++ b/certs/system_certificates.S
@@ -13,6 +13,18 @@
.incbin "certs/x509_certificate_list"
__cert_list_end:
+#ifdef CONFIG_SYSTEM_EXTRA_CERTIFICATE
+ .globl VMLINUX_SYMBOL(system_extra_cert)
+ .size system_extra_cert, CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE
+VMLINUX_SYMBOL(system_extra_cert):
+ .fill CONFIG_SYSTEM_EXTRA_CERTIFICATE_SIZE, 1, 0
+
+ .globl VMLINUX_SYMBOL(system_extra_cert_used)
+VMLINUX_SYMBOL(system_extra_cert_used):
+ .int 0
+
+#endif /* CONFIG_SYSTEM_EXTRA_CERTIFICATE */
+
.align 8
.globl VMLINUX_SYMBOL(system_certificate_list_size)
VMLINUX_SYMBOL(system_certificate_list_size):
diff --git a/scripts/.gitignore b/scripts/.gitignore
index 1f78169..e063daa 100644
--- a/scripts/.gitignore
+++ b/scripts/.gitignore
@@ -13,3 +13,4 @@
asn1_compiler
extract-cert
sign-file
+insert-sys-cert
diff --git a/scripts/Makefile b/scripts/Makefile
index fd0d53d..822ab4a 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -19,6 +19,7 @@
hostprogs-$(CONFIG_ASN1) += asn1_compiler
hostprogs-$(CONFIG_MODULE_SIG) += sign-file
hostprogs-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += extract-cert
+hostprogs-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE) += insert-sys-cert
HOSTCFLAGS_sortextable.o = -I$(srctree)/tools/include
HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
diff --git a/scripts/insert-sys-cert.c b/scripts/insert-sys-cert.c
new file mode 100644
index 0000000..8902836
--- /dev/null
+++ b/scripts/insert-sys-cert.c
@@ -0,0 +1,410 @@
+/* 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>
+ */
+
+#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 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);
+}