/* Copyright 2014 The ChromiumOS Authors * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. */ #include #include #include #include #include #include #include "elfparse.h" #include "util.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; attribute_cleanup_fp 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; } } return ret; }