Jorge Lucangeli Obes | d613ab2 | 2015-03-03 14:22:50 -0800 | [diff] [blame] | 1 | /* Copyright (c) 2014 The Chromium OS Authors. All rights reserved. |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 2 | * Use of this source code is governed by a BSD-style license that can be |
| 3 | * found in the LICENSE file. |
| 4 | */ |
| 5 | |
| 6 | #include "elfparse.h" |
| 7 | |
| 8 | int is_elf_magic (const uint8_t *buf) |
| 9 | { |
| 10 | return (buf[EI_MAG0] == ELFMAG0) && |
| 11 | (buf[EI_MAG1] == ELFMAG1) && |
| 12 | (buf[EI_MAG2] == ELFMAG2) && |
| 13 | (buf[EI_MAG3] == ELFMAG3); |
| 14 | } |
| 15 | |
| 16 | #define parseElftemplate(bit) \ |
| 17 | ElfType parseElf ## bit(FILE *elf_file, uint8_t *pHead, int little_endian) \ |
| 18 | { \ |
| 19 | ElfType ret = ELFSTATIC; \ |
| 20 | Minijail_Elf ## bit ## _Ehdr *pHeader = NULL; \ |
| 21 | Minijail_Elf ## bit ## _Phdr pheader = { 0 }; \ |
| 22 | uint32_t i = 0; \ |
| 23 | \ |
| 24 | if (!elf_file || !pHead) \ |
| 25 | return ELFERROR; \ |
| 26 | \ |
| 27 | pHeader = (Minijail_Elf ## bit ## _Ehdr *)pHead; \ |
| 28 | if (little_endian) { \ |
| 29 | pHeader->e_phoff = le ## bit ## toh(pHeader->e_phoff); \ |
| 30 | pHeader->e_phentsize = le16toh(pHeader->e_phentsize); \ |
| 31 | pHeader->e_phnum = le16toh(pHeader->e_phnum); \ |
| 32 | } else { \ |
| 33 | pHeader->e_phoff = be ## bit ## toh(pHeader->e_phoff); \ |
| 34 | pHeader->e_phentsize = be16toh(pHeader->e_phentsize); \ |
| 35 | pHeader->e_phnum = be16toh(pHeader->e_phnum); \ |
| 36 | } \ |
| 37 | if (pHeader->e_phentsize != sizeof(Minijail_Elf ## bit ## _Phdr)) \ |
| 38 | return ELFERROR; \ |
| 39 | \ |
| 40 | if (fseek(elf_file, pHeader->e_phoff, SEEK_SET) != 0) \ |
| 41 | return ELFERROR; \ |
| 42 | \ |
| 43 | for (i = 0; i < pHeader->e_phnum; i++) { \ |
| 44 | if (fread(&pheader, sizeof(pheader), 1, elf_file) == 1) { \ |
| 45 | if (pheader.p_type == PT_INTERP) { \ |
| 46 | ret = ELFDYNAMIC; \ |
| 47 | break; \ |
| 48 | } \ |
| 49 | } else { \ |
| 50 | ret = ELFERROR; \ |
| 51 | break; \ |
| 52 | } \ |
| 53 | } \ |
| 54 | return ret; \ |
| 55 | } |
| 56 | parseElftemplate(64) |
| 57 | parseElftemplate(32) |
| 58 | |
| 59 | /* Public function to determine the linkage of an ELF. */ |
| 60 | ElfType get_elf_linkage(const char *path) |
| 61 | { |
| 62 | ElfType ret = ELFERROR; |
| 63 | FILE *elf_file = NULL; |
| 64 | uint8_t pHeader[HEADERSIZE] = ""; |
| 65 | |
| 66 | elf_file = fopen(path, "r"); |
| 67 | if (elf_file) { |
| 68 | if (fread(pHeader, 1, HEADERSIZE, elf_file) == HEADERSIZE) { |
| 69 | if (is_elf_magic(pHeader)) { |
| 70 | if ((pHeader[EI_DATA] == ELFDATA2LSB) && |
| 71 | (pHeader[EI_CLASS] == ELFCLASS64)) { |
Jorge Lucangeli Obes | 768d42b | 2016-02-17 10:28:25 -0800 | [diff] [blame] | 72 | /* 64-bit little endian. */ |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 73 | ret = parseElf64(elf_file, pHeader, 1); |
| 74 | } else if ((pHeader[EI_DATA] == ELFDATA2MSB) && |
| 75 | (pHeader[EI_CLASS] == ELFCLASS64)) { |
Jorge Lucangeli Obes | 768d42b | 2016-02-17 10:28:25 -0800 | [diff] [blame] | 76 | /* 64-bit big endian. */ |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 77 | ret = parseElf64(elf_file, pHeader, 0); |
| 78 | } else if ((pHeader[EI_DATA] == ELFDATA2LSB) && |
| 79 | (pHeader[EI_CLASS] == ELFCLASS32)) { |
Jorge Lucangeli Obes | 768d42b | 2016-02-17 10:28:25 -0800 | [diff] [blame] | 80 | /* 32-bit little endian. */ |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 81 | ret = parseElf32(elf_file, pHeader, 1); |
| 82 | } else if ((pHeader[EI_DATA] == ELFDATA2MSB) && |
| 83 | (pHeader[EI_CLASS] == ELFCLASS32)) { |
Jorge Lucangeli Obes | 768d42b | 2016-02-17 10:28:25 -0800 | [diff] [blame] | 84 | /* 32-bit big endian. */ |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 85 | ret = parseElf32(elf_file, pHeader, 0); |
| 86 | } |
| 87 | } else { |
| 88 | /* |
| 89 | * The binary is not an ELF. We assume it's a |
| 90 | * script. We should parse the #! line and |
| 91 | * check the interpreter to guard against |
| 92 | * static interpreters escaping the sandbox. |
Jorge Lucangeli Obes | 768d42b | 2016-02-17 10:28:25 -0800 | [diff] [blame] | 93 | * As Minijail is only called from the rootfs |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 94 | * it was deemed not necessary to check this. |
Jorge Lucangeli Obes | 768d42b | 2016-02-17 10:28:25 -0800 | [diff] [blame] | 95 | * So we will just let execve(2) decide if this |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 96 | * is valid. |
| 97 | */ |
| 98 | ret = ELFDYNAMIC; |
| 99 | } |
| 100 | } else { |
Jorge Lucangeli Obes | 2f61ee4 | 2014-06-16 11:08:18 -0700 | [diff] [blame] | 101 | /* |
| 102 | * The file is smaller than |HEADERSIZE| bytes. |
| 103 | * We assume it's a short script. See above for |
| 104 | * reasoning on scripts. |
| 105 | */ |
Lee Campbell | 1e4fc6a | 2014-06-06 17:40:02 -0700 | [diff] [blame] | 106 | ret = ELFDYNAMIC; |
| 107 | } |
| 108 | fclose(elf_file); |
| 109 | } |
| 110 | return ret; |
| 111 | } |