blob: e76ebc48077ab98e2051f4f06f408ebf937731be [file] [log] [blame]
/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include <elf.h>
#include <endian.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "elfparse.h"
int is_elf_magic (const uint8_t *buf)
{
return (buf[EI_MAG0] == ELFMAG0) &&
(buf[EI_MAG1] == ELFMAG1) &&
(buf[EI_MAG2] == ELFMAG2) &&
(buf[EI_MAG3] == ELFMAG3);
}
#define parseElftemplate(bit) \
ElfType parseElf ## bit(FILE *elf_file, uint8_t *pHead, int little_endian) \
{ \
ElfType ret = ELFSTATIC; \
Minijail_Elf ## bit ## _Ehdr *pHeader = NULL; \
Minijail_Elf ## bit ## _Phdr pheader; \
uint32_t i = 0; \
\
if (!elf_file || !pHead) \
return ELFERROR; \
\
pHeader = (Minijail_Elf ## bit ## _Ehdr *)pHead; \
if (little_endian) { \
pHeader->e_phoff = le ## bit ## toh(pHeader->e_phoff); \
pHeader->e_phentsize = le16toh(pHeader->e_phentsize); \
pHeader->e_phnum = le16toh(pHeader->e_phnum); \
} else { \
pHeader->e_phoff = be ## bit ## toh(pHeader->e_phoff); \
pHeader->e_phentsize = be16toh(pHeader->e_phentsize); \
pHeader->e_phnum = be16toh(pHeader->e_phnum); \
} \
if (pHeader->e_phentsize != sizeof(Minijail_Elf ## bit ## _Phdr)) \
return ELFERROR; \
\
if (fseek(elf_file, pHeader->e_phoff, SEEK_SET) != 0) \
return ELFERROR; \
\
for (i = 0; i < pHeader->e_phnum; i++) { \
if (fread(&pheader, sizeof(pheader), 1, elf_file) == 1) { \
if (pheader.p_type == PT_INTERP) { \
ret = ELFDYNAMIC; \
break; \
} \
} else { \
ret = ELFERROR; \
break; \
} \
} \
return ret; \
}
parseElftemplate(64)
parseElftemplate(32)
/* Public function to determine the linkage of an ELF. */
ElfType get_elf_linkage(const char *path)
{
ElfType ret = ELFERROR;
FILE *elf_file = NULL;
uint8_t pHeader[HEADERSIZE] = "";
elf_file = fopen(path, "re");
if (elf_file) {
if (fread(pHeader, 1, HEADERSIZE, elf_file) == HEADERSIZE) {
if (is_elf_magic(pHeader)) {
if ((pHeader[EI_DATA] == ELFDATA2LSB) &&
(pHeader[EI_CLASS] == ELFCLASS64)) {
/* 64-bit little endian. */
ret = parseElf64(elf_file, pHeader, 1);
} else if ((pHeader[EI_DATA] == ELFDATA2MSB) &&
(pHeader[EI_CLASS] == ELFCLASS64)) {
/* 64-bit big endian. */
ret = parseElf64(elf_file, pHeader, 0);
} else if ((pHeader[EI_DATA] == ELFDATA2LSB) &&
(pHeader[EI_CLASS] == ELFCLASS32)) {
/* 32-bit little endian. */
ret = parseElf32(elf_file, pHeader, 1);
} else if ((pHeader[EI_DATA] == ELFDATA2MSB) &&
(pHeader[EI_CLASS] == ELFCLASS32)) {
/* 32-bit big endian. */
ret = parseElf32(elf_file, pHeader, 0);
}
} else {
/*
* The binary is not an ELF. We assume it's a
* script. We should parse the #! line and
* check the interpreter to guard against
* static interpreters escaping the sandbox.
* As Minijail is only called from the rootfs
* it was deemed not necessary to check this.
* So we will just let execve(2) decide if this
* is valid.
*/
ret = ELFDYNAMIC;
}
} else {
/*
* The file is smaller than |HEADERSIZE| bytes.
* We assume it's a short script. See above for
* reasoning on scripts.
*/
ret = ELFDYNAMIC;
}
fclose(elf_file);
}
return ret;
}