blob: 96caa59c87f149b61a37a06c809a50061708d4ee [file] [log] [blame]
Jorge Lucangeli Obesd613ab22015-03-03 14:22:50 -08001/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
Lee Campbell1e4fc6a2014-06-06 17:40:02 -07002 * Use of this source code is governed by a BSD-style license that can be
3 * found in the LICENSE file.
4 */
5
Mike Frysinger37c8e3c2018-01-20 13:47:08 -05006#include <elf.h>
7#include <endian.h>
8#include <stdint.h>
9#include <stdio.h>
10#include <stdlib.h>
11#include <unistd.h>
12
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070013#include "elfparse.h"
Mike Frysingerdebdf5d2021-06-21 09:52:06 -040014#include "util.h"
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070015
16int is_elf_magic (const uint8_t *buf)
17{
18 return (buf[EI_MAG0] == ELFMAG0) &&
19 (buf[EI_MAG1] == ELFMAG1) &&
20 (buf[EI_MAG2] == ELFMAG2) &&
21 (buf[EI_MAG3] == ELFMAG3);
22}
23
24#define parseElftemplate(bit) \
25ElfType parseElf ## bit(FILE *elf_file, uint8_t *pHead, int little_endian) \
26{ \
27 ElfType ret = ELFSTATIC; \
28 Minijail_Elf ## bit ## _Ehdr *pHeader = NULL; \
Mike Frysinger06cacc92018-01-24 14:52:41 -050029 Minijail_Elf ## bit ## _Phdr pheader; \
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070030 uint32_t i = 0; \
31 \
32 if (!elf_file || !pHead) \
33 return ELFERROR; \
34 \
35 pHeader = (Minijail_Elf ## bit ## _Ehdr *)pHead; \
36 if (little_endian) { \
37 pHeader->e_phoff = le ## bit ## toh(pHeader->e_phoff); \
38 pHeader->e_phentsize = le16toh(pHeader->e_phentsize); \
39 pHeader->e_phnum = le16toh(pHeader->e_phnum); \
40 } else { \
41 pHeader->e_phoff = be ## bit ## toh(pHeader->e_phoff); \
42 pHeader->e_phentsize = be16toh(pHeader->e_phentsize); \
43 pHeader->e_phnum = be16toh(pHeader->e_phnum); \
44 } \
45 if (pHeader->e_phentsize != sizeof(Minijail_Elf ## bit ## _Phdr)) \
46 return ELFERROR; \
47 \
48 if (fseek(elf_file, pHeader->e_phoff, SEEK_SET) != 0) \
49 return ELFERROR; \
50 \
51 for (i = 0; i < pHeader->e_phnum; i++) { \
52 if (fread(&pheader, sizeof(pheader), 1, elf_file) == 1) { \
53 if (pheader.p_type == PT_INTERP) { \
54 ret = ELFDYNAMIC; \
55 break; \
56 } \
57 } else { \
58 ret = ELFERROR; \
59 break; \
60 } \
61 } \
62 return ret; \
63}
64parseElftemplate(64)
65parseElftemplate(32)
66
67/* Public function to determine the linkage of an ELF. */
68ElfType get_elf_linkage(const char *path)
69{
70 ElfType ret = ELFERROR;
Mike Frysingerdebdf5d2021-06-21 09:52:06 -040071 attribute_cleanup_fp FILE *elf_file = NULL;
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070072 uint8_t pHeader[HEADERSIZE] = "";
73
Luis Hector Chaveza30a2062018-07-12 21:10:33 -070074 elf_file = fopen(path, "re");
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070075 if (elf_file) {
76 if (fread(pHeader, 1, HEADERSIZE, elf_file) == HEADERSIZE) {
77 if (is_elf_magic(pHeader)) {
78 if ((pHeader[EI_DATA] == ELFDATA2LSB) &&
79 (pHeader[EI_CLASS] == ELFCLASS64)) {
Jorge Lucangeli Obes768d42b2016-02-17 10:28:25 -080080 /* 64-bit little endian. */
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070081 ret = parseElf64(elf_file, pHeader, 1);
82 } else if ((pHeader[EI_DATA] == ELFDATA2MSB) &&
83 (pHeader[EI_CLASS] == ELFCLASS64)) {
Jorge Lucangeli Obes768d42b2016-02-17 10:28:25 -080084 /* 64-bit big endian. */
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070085 ret = parseElf64(elf_file, pHeader, 0);
86 } else if ((pHeader[EI_DATA] == ELFDATA2LSB) &&
87 (pHeader[EI_CLASS] == ELFCLASS32)) {
Jorge Lucangeli Obes768d42b2016-02-17 10:28:25 -080088 /* 32-bit little endian. */
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070089 ret = parseElf32(elf_file, pHeader, 1);
90 } else if ((pHeader[EI_DATA] == ELFDATA2MSB) &&
91 (pHeader[EI_CLASS] == ELFCLASS32)) {
Jorge Lucangeli Obes768d42b2016-02-17 10:28:25 -080092 /* 32-bit big endian. */
Lee Campbell1e4fc6a2014-06-06 17:40:02 -070093 ret = parseElf32(elf_file, pHeader, 0);
94 }
95 } else {
96 /*
97 * The binary is not an ELF. We assume it's a
98 * script. We should parse the #! line and
99 * check the interpreter to guard against
100 * static interpreters escaping the sandbox.
Jorge Lucangeli Obes768d42b2016-02-17 10:28:25 -0800101 * As Minijail is only called from the rootfs
Lee Campbell1e4fc6a2014-06-06 17:40:02 -0700102 * it was deemed not necessary to check this.
Jorge Lucangeli Obes768d42b2016-02-17 10:28:25 -0800103 * So we will just let execve(2) decide if this
Lee Campbell1e4fc6a2014-06-06 17:40:02 -0700104 * is valid.
105 */
106 ret = ELFDYNAMIC;
107 }
108 } else {
Jorge Lucangeli Obes2f61ee42014-06-16 11:08:18 -0700109 /*
110 * The file is smaller than |HEADERSIZE| bytes.
111 * We assume it's a short script. See above for
112 * reasoning on scripts.
113 */
Lee Campbell1e4fc6a2014-06-06 17:40:02 -0700114 ret = ELFDYNAMIC;
115 }
Lee Campbell1e4fc6a2014-06-06 17:40:02 -0700116 }
117 return ret;
118}