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