KEYS: Reserve an extra certificate symbol for inserting without recompiling (c4c36105) · Commits · 戴 / test

certs/Kconfig

+16 −0

Original line number	Diff line number	Diff line
		@@ -39,4 +39,20 @@ config SYSTEM_TRUSTED_KEYS
		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

certs/system_certificates.S

+12 −0

Original line number	Diff line number	Diff line
		@@ -13,6 +13,18 @@ __cert_list_start:
		.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):

scripts/.gitignore

+1 −0

Original line number	Diff line number	Diff line
		@@ -13,3 +13,4 @@ sortextable
		asn1_compiler
		extract-cert
		sign-file
		insert-sys-cert

scripts/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -19,6 +19,7 @@ hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable
		hostprogs-$(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

scripts/insert-sys-cert.c

0 → 100644

+410 −0

Original line number	Diff line number	Diff line
		/* 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);
		}

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