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grub/grub-core/kern/elf.c
Alec Brown ddb6c1bafb elf: Validate number of elf program header table entries 
In bsdXX.c and multiboot_elfxx.c, e_phnum is used to obtain the number of
program header table entries, but it wasn't being checked if the value was
there.

According to the elf(5) manual page,
"If the number of entries in the program header table is larger than or equal to
PN_XNUM (0xffff), this member holds PN_XNUM (0xffff) and the real number of
entries in the program header table is held in the sh_info member of the
initial entry in section header table.  Otherwise, the sh_info member of the
initial entry contains the value zero."

Since this check wasn't being made, grub_elfXX_get_phnum() is being added to
elfXX.c to make this check and use e_phnum if it doesn't have PN_XNUM as a
value, else use sh_info. We also need to make sure e_phnum isn't greater than
PN_XNUM and sh_info isn't less than PN_XNUM.

Note that even though elf.c and elfXX.c are located in grub-core/kern, they are
compiled as modules and don't need the EXPORT_FUNC() macro to define the functions
in elf.h.

Also, changed casts of phnum to match variables being set as well as dropped
casts when unnecessary.

Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
2022-08-19 22:27:51 +02:00

231 lines
6.1 KiB
C
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/* elf.c - load ELF files */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2003,2004,2005,2006,2007,2008,2009 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/err.h>
#include <grub/elf.h>
#include <grub/elfload.h>
#include <grub/file.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/dl.h>
#include <grub/i18n.h>
GRUB_MOD_LICENSE ("GPLv3+");
#pragma GCC diagnostic ignored "-Wcast-align"
#if defined(__powerpc__) && defined(GRUB_MACHINE_IEEE1275)
#define GRUB_ELF_ENABLE_BI_ENDIAN 1
#else
#define GRUB_ELF_ENABLE_BI_ENDIAN 0
#endif
#if defined(GRUB_CPU_WORDS_BIGENDIAN)
#define GRUB_ELF_NATIVE_ENDIANNESS ELFDATA2MSB
#define GRUB_ELF_OPPOSITE_ENDIANNESS ELFDATA2LSB
#else
#define GRUB_ELF_NATIVE_ENDIANNESS ELFDATA2LSB
#define GRUB_ELF_OPPOSITE_ENDIANNESS ELFDATA2MSB
#endif
static int grub_elf32_check_endianess_and_bswap_ehdr (grub_elf_t elf);
static int grub_elf64_check_endianess_and_bswap_ehdr (grub_elf_t elf);
/* Check if EHDR is a valid ELF header. */
static grub_err_t
grub_elf_check_header (grub_elf_t elf)
{
Elf32_Ehdr *e = &elf->ehdr.ehdr32;
if (e->e_ident[EI_MAG0] != ELFMAG0
|| e->e_ident[EI_MAG1] != ELFMAG1
|| e->e_ident[EI_MAG2] != ELFMAG2
|| e->e_ident[EI_MAG3] != ELFMAG3
|| e->e_ident[EI_VERSION] != EV_CURRENT)
return grub_error (GRUB_ERR_BAD_OS, N_("invalid arch-independent ELF magic"));
if (grub_elf_is_elf32 (elf))
{
if (!grub_elf32_check_endianess_and_bswap_ehdr (elf)) {
return grub_error (GRUB_ERR_BAD_OS, "invalid ELF endianness magic");
}
}
else if (grub_elf_is_elf64 (elf))
{
if (!grub_elf64_check_endianess_and_bswap_ehdr (elf)) {
return grub_error (GRUB_ERR_BAD_OS, "invalid ELF endianness magic");
}
}
else
return grub_error (GRUB_ERR_BAD_OS, "unknown ELF class");
if (e->e_version != EV_CURRENT)
return grub_error (GRUB_ERR_BAD_OS, N_("invalid arch-independent ELF magic"));
return GRUB_ERR_NONE;
}
grub_err_t
grub_elf_close (grub_elf_t elf)
{
grub_file_t file = elf->file;
grub_free (elf->phdrs);
grub_free (elf->filename);
grub_free (elf);
if (file)
grub_file_close (file);
return grub_errno;
}
grub_elf_t
grub_elf_file (grub_file_t file, const char *filename)
{
grub_elf_t elf;
elf = grub_zalloc (sizeof (*elf));
if (! elf)
return 0;
elf->file = file;
if (grub_file_seek (elf->file, 0) == (grub_off_t) -1)
goto fail;
if (grub_file_read (elf->file, &elf->ehdr, sizeof (elf->ehdr))
!= sizeof (elf->ehdr))
{
if (!grub_errno)
grub_error (GRUB_ERR_FILE_READ_ERROR, N_("premature end of file %s"),
filename);
goto fail;
}
if (grub_elf_check_header (elf))
goto fail;
elf->filename = grub_strdup (filename);
if (!elf->filename)
goto fail;
return elf;
fail:
grub_free (elf->filename);
grub_free (elf->phdrs);
grub_free (elf);
return 0;
}
grub_elf_t
grub_elf_open (const char *name, enum grub_file_type type)
{
grub_file_t file;
grub_elf_t elf;
file = grub_file_open (name, type);
if (! file)
return 0;
elf = grub_elf_file (file, name);
if (! elf)
grub_file_close (file);
return elf;
}
#define grub_swap_bytes_halfXX grub_swap_bytes16
#define grub_swap_bytes_wordXX grub_swap_bytes32
/* 32-bit */
#define ehdrXX ehdr32
#define ELFCLASSXX ELFCLASS32
#define ElfXX_Addr Elf32_Addr
#define grub_elfXX_size grub_elf32_size
#define grub_elfXX_load grub_elf32_load
#define FOR_ELFXX_PHDRS FOR_ELF32_PHDRS
#define grub_elf_is_elfXX grub_elf_is_elf32
#define grub_elfXX_load_phdrs grub_elf32_load_phdrs
#define ElfXX_Phdr Elf32_Phdr
#define ElfXX_Ehdr Elf32_Ehdr
#define ElfXX_Shdr Elf32_Shdr
#define ElfXX_Word Elf32_Word
#define ElfXX_Shnum Elf32_Shnum
#define grub_uintXX_t grub_uint32_t
#define grub_swap_bytes_addrXX grub_swap_bytes32
#define grub_swap_bytes_offXX grub_swap_bytes32
#define grub_swap_bytes_XwordXX grub_swap_bytes32
#define grub_elfXX_check_endianess_and_bswap_ehdr grub_elf32_check_endianess_and_bswap_ehdr
#define grub_elfXX_get_shnum grub_elf32_get_shnum
#define grub_elfXX_get_shstrndx grub_elf32_get_shstrndx
#define grub_elfXX_get_phnum grub_elf32_get_phnum
#include "elfXX.c"
#undef ehdrXX
#undef ELFCLASSXX
#undef ElfXX_Addr
#undef grub_elfXX_size
#undef grub_elfXX_load
#undef FOR_ELFXX_PHDRS
#undef grub_elf_is_elfXX
#undef grub_elfXX_load_phdrs
#undef ElfXX_Phdr
#undef ElfXX_Ehdr
#undef ElfXX_Shdr
#undef ElfXX_Word
#undef ElfXX_Shnum
#undef grub_uintXX_t
#undef grub_swap_bytes_addrXX
#undef grub_swap_bytes_offXX
#undef grub_swap_bytes_XwordXX
#undef grub_elfXX_check_endianess_and_bswap_ehdr
#undef grub_elfXX_get_shnum
#undef grub_elfXX_get_shstrndx
#undef grub_elfXX_get_phnum
/* 64-bit */
#define ehdrXX ehdr64
#define ELFCLASSXX ELFCLASS64
#define ElfXX_Addr Elf64_Addr
#define grub_elfXX_size grub_elf64_size
#define grub_elfXX_load grub_elf64_load
#define FOR_ELFXX_PHDRS FOR_ELF64_PHDRS
#define grub_elf_is_elfXX grub_elf_is_elf64
#define grub_elfXX_load_phdrs grub_elf64_load_phdrs
#define ElfXX_Phdr Elf64_Phdr
#define ElfXX_Ehdr Elf64_Ehdr
#define ElfXX_Shdr Elf64_Shdr
#define ElfXX_Word Elf64_Word
#define ElfXX_Shnum Elf64_Shnum
#define grub_uintXX_t grub_uint64_t
#define grub_swap_bytes_addrXX grub_swap_bytes64
#define grub_swap_bytes_offXX grub_swap_bytes64
#define grub_swap_bytes_XwordXX grub_swap_bytes64
#define grub_elfXX_check_endianess_and_bswap_ehdr grub_elf64_check_endianess_and_bswap_ehdr
#define grub_elfXX_get_shnum grub_elf64_get_shnum
#define grub_elfXX_get_shstrndx grub_elf64_get_shstrndx
#define grub_elfXX_get_phnum grub_elf64_get_phnum
#include "elfXX.c"
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