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/*
* Copyright (C) 2014-2020 Firejail Authors
*
* This file is part of firejail project
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/*
This code borrows heavily from src/libappimage_shared/elf.c in libappimage
*/
/*
Compile with:
gcc elfsize.c -o elfsize
Example:
ls -l 126584
Calculation using the values also reported by readelf -h:
Start of section headers e_shoff 124728
Size of section headers e_shentsize 64
Number of section headers e_shnum 29
e_shoff + ( e_shentsize * e_shnum ) = 126584
*/
#include <elf.h>
#include <byteswap.h>
#include <stdio.h>
#include <stdint.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
typedef Elf32_Nhdr Elf_Nhdr;
static Elf64_Ehdr ehdr;
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define ELFDATANATIVE ELFDATA2LSB
#elif __BYTE_ORDER == __BIG_ENDIAN
#define ELFDATANATIVE ELFDATA2MSB
#else
#error "Unknown machine endian"
#endif
static uint16_t file16_to_cpu(uint16_t val) {
if (ehdr.e_ident[EI_DATA] != ELFDATANATIVE)
val = bswap_16(val);
return val;
}
static uint32_t file32_to_cpu(uint32_t val) {
if (ehdr.e_ident[EI_DATA] != ELFDATANATIVE)
val = bswap_32(val);
return val;
}
static uint64_t file64_to_cpu(uint64_t val) {
if (ehdr.e_ident[EI_DATA] != ELFDATANATIVE)
val = bswap_64(val);
return val;
}
// return 0 if error
static long unsigned int read_elf32(int fd) {
Elf32_Ehdr ehdr32;
Elf32_Shdr shdr32;
off_t last_shdr_offset;
ssize_t ret;
unsigned long sht_end, last_section_end;
ret = pread(fd, &ehdr32, sizeof(ehdr32), 0);
if (ret < 0 || (size_t)ret != sizeof(ehdr))
return 0;
ehdr.e_shoff = file32_to_cpu(ehdr32.e_shoff);
ehdr.e_shentsize = file16_to_cpu(ehdr32.e_shentsize);
ehdr.e_shnum = file16_to_cpu(ehdr32.e_shnum);
last_shdr_offset = ehdr.e_shoff + (ehdr.e_shentsize * (ehdr.e_shnum - 1));
ret = pread(fd, &shdr32, sizeof(shdr32), last_shdr_offset);
if (ret < 0 || (size_t)ret != sizeof(shdr32))
return 0;
/* ELF ends either with the table of section headers (SHT) or with a section. */
sht_end = ehdr.e_shoff + (ehdr.e_shentsize * ehdr.e_shnum);
last_section_end = file64_to_cpu(shdr32.sh_offset) + file64_to_cpu(shdr32.sh_size);
return sht_end > last_section_end ? sht_end : last_section_end;
}
// return 0 if error
static long unsigned int read_elf64(int fd) {
Elf64_Ehdr ehdr64;
Elf64_Shdr shdr64;
off_t last_shdr_offset;
ssize_t ret;
unsigned long sht_end, last_section_end;
ret = pread(fd, &ehdr64, sizeof(ehdr64), 0);
if (ret < 0 || (size_t)ret != sizeof(ehdr))
return 0;
ehdr.e_shoff = file64_to_cpu(ehdr64.e_shoff);
ehdr.e_shentsize = file16_to_cpu(ehdr64.e_shentsize);
ehdr.e_shnum = file16_to_cpu(ehdr64.e_shnum);
last_shdr_offset = ehdr.e_shoff + (ehdr.e_shentsize * (ehdr.e_shnum - 1));
ret = pread(fd, &shdr64, sizeof(shdr64), last_shdr_offset);
if (ret < 0 || (size_t)ret != sizeof(shdr64))
return 0;
/* ELF ends either with the table of section headers (SHT) or with a section. */
sht_end = ehdr.e_shoff + (ehdr.e_shentsize * ehdr.e_shnum);
last_section_end = file64_to_cpu(shdr64.sh_offset) + file64_to_cpu(shdr64.sh_size);
return sht_end > last_section_end ? sht_end : last_section_end;
}
// return 0 if error
// return 0 if this is not an appimgage2 file
long unsigned int appimage2_size(const char *fname) {
ssize_t ret;
int fd;
long unsigned int size = 0;
fd = open(fname, O_RDONLY);
if (fd < 0)
return 0;
ret = pread(fd, ehdr.e_ident, EI_NIDENT, 0);
if (ret != EI_NIDENT)
goto getout;
if ((ehdr.e_ident[EI_DATA] != ELFDATA2LSB) &&
(ehdr.e_ident[EI_DATA] != ELFDATA2MSB))
goto getout;
if(ehdr.e_ident[EI_CLASS] == ELFCLASS32) {
size = read_elf32(fd);
}
else if(ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
size = read_elf64(fd);
}
else {
goto getout;
}
if (size == 0)
goto getout;
// look for a LZMA header at this location
unsigned char buf[4];
ret = pread(fd, buf, 4, size);
if (ret != 4) {
size = 0;
goto getout;
}
if (memcmp(buf, "hsqs", 4) != 0)
size = 0;
getout:
close(fd);
return size;
}
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