1 /*
2 * vpd_decode.c
3 *
4 * Google VPD decoding routines.
5 *
6 * Copyright 2017 Google Inc.
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License v2.0 as published by
10 * the Free Software Foundation.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 */
17
18 #include <linux/export.h>
19
20 #include "vpd_decode.h"
21
vpd_decode_len(const u32 max_len,const u8 * in,u32 * length,u32 * decoded_len)22 static int vpd_decode_len(const u32 max_len, const u8 *in,
23 u32 *length, u32 *decoded_len)
24 {
25 u8 more;
26 int i = 0;
27
28 if (!length || !decoded_len)
29 return VPD_FAIL;
30
31 *length = 0;
32 do {
33 if (i >= max_len)
34 return VPD_FAIL;
35
36 more = in[i] & 0x80;
37 *length <<= 7;
38 *length |= in[i] & 0x7f;
39 ++i;
40 } while (more);
41
42 *decoded_len = i;
43 return VPD_OK;
44 }
45
vpd_decode_entry(const u32 max_len,const u8 * input_buf,u32 * _consumed,const u8 ** entry,u32 * entry_len)46 static int vpd_decode_entry(const u32 max_len, const u8 *input_buf,
47 u32 *_consumed, const u8 **entry, u32 *entry_len)
48 {
49 u32 decoded_len;
50 u32 consumed = *_consumed;
51
52 if (vpd_decode_len(max_len - consumed, &input_buf[consumed],
53 entry_len, &decoded_len) != VPD_OK)
54 return VPD_FAIL;
55 if (max_len - consumed < decoded_len)
56 return VPD_FAIL;
57
58 consumed += decoded_len;
59 *entry = input_buf + consumed;
60
61 /* entry_len is untrusted data and must be checked again. */
62 if (max_len - consumed < *entry_len)
63 return VPD_FAIL;
64
65 consumed += *entry_len;
66 *_consumed = consumed;
67 return VPD_OK;
68 }
69
vpd_decode_string(const u32 max_len,const u8 * input_buf,u32 * consumed,vpd_decode_callback callback,void * callback_arg)70 int vpd_decode_string(const u32 max_len, const u8 *input_buf, u32 *consumed,
71 vpd_decode_callback callback, void *callback_arg)
72 {
73 int type;
74 u32 key_len;
75 u32 value_len;
76 const u8 *key;
77 const u8 *value;
78
79 /* type */
80 if (*consumed >= max_len)
81 return VPD_FAIL;
82
83 type = input_buf[*consumed];
84
85 switch (type) {
86 case VPD_TYPE_INFO:
87 case VPD_TYPE_STRING:
88 (*consumed)++;
89
90 if (vpd_decode_entry(max_len, input_buf, consumed, &key,
91 &key_len) != VPD_OK)
92 return VPD_FAIL;
93
94 if (vpd_decode_entry(max_len, input_buf, consumed, &value,
95 &value_len) != VPD_OK)
96 return VPD_FAIL;
97
98 if (type == VPD_TYPE_STRING)
99 return callback(key, key_len, value, value_len,
100 callback_arg);
101 break;
102
103 default:
104 return VPD_FAIL;
105 }
106
107 return VPD_OK;
108 }
109