1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * vpd_decode.c |
4 | * |
5 | * Google VPD decoding routines. |
6 | * |
7 | * Copyright 2017 Google Inc. |
8 | */ |
9 | |
10 | #include "vpd_decode.h" |
11 | |
12 | static int vpd_decode_len(const u32 max_len, const u8 *in, |
13 | u32 *length, u32 *decoded_len) |
14 | { |
15 | u8 more; |
16 | int i = 0; |
17 | |
18 | if (!length || !decoded_len) |
19 | return VPD_FAIL; |
20 | |
21 | *length = 0; |
22 | do { |
23 | if (i >= max_len) |
24 | return VPD_FAIL; |
25 | |
26 | more = in[i] & 0x80; |
27 | *length <<= 7; |
28 | *length |= in[i] & 0x7f; |
29 | ++i; |
30 | } while (more); |
31 | |
32 | *decoded_len = i; |
33 | return VPD_OK; |
34 | } |
35 | |
36 | static int vpd_decode_entry(const u32 max_len, const u8 *input_buf, |
37 | u32 *_consumed, const u8 **entry, u32 *entry_len) |
38 | { |
39 | u32 decoded_len; |
40 | u32 consumed = *_consumed; |
41 | |
42 | if (vpd_decode_len(max_len: max_len - consumed, in: &input_buf[consumed], |
43 | length: entry_len, decoded_len: &decoded_len) != VPD_OK) |
44 | return VPD_FAIL; |
45 | if (max_len - consumed < decoded_len) |
46 | return VPD_FAIL; |
47 | |
48 | consumed += decoded_len; |
49 | *entry = input_buf + consumed; |
50 | |
51 | /* entry_len is untrusted data and must be checked again. */ |
52 | if (max_len - consumed < *entry_len) |
53 | return VPD_FAIL; |
54 | |
55 | consumed += *entry_len; |
56 | *_consumed = consumed; |
57 | return VPD_OK; |
58 | } |
59 | |
60 | int vpd_decode_string(const u32 max_len, const u8 *input_buf, u32 *consumed, |
61 | vpd_decode_callback callback, void *callback_arg) |
62 | { |
63 | int type; |
64 | u32 key_len; |
65 | u32 value_len; |
66 | const u8 *key; |
67 | const u8 *value; |
68 | |
69 | /* type */ |
70 | if (*consumed >= max_len) |
71 | return VPD_FAIL; |
72 | |
73 | type = input_buf[*consumed]; |
74 | |
75 | switch (type) { |
76 | case VPD_TYPE_INFO: |
77 | case VPD_TYPE_STRING: |
78 | (*consumed)++; |
79 | |
80 | if (vpd_decode_entry(max_len, input_buf, consumed: consumed, entry: &key, |
81 | entry_len: &key_len) != VPD_OK) |
82 | return VPD_FAIL; |
83 | |
84 | if (vpd_decode_entry(max_len, input_buf, consumed: consumed, entry: &value, |
85 | entry_len: &value_len) != VPD_OK) |
86 | return VPD_FAIL; |
87 | |
88 | if (type == VPD_TYPE_STRING) |
89 | return callback(key, key_len, value, value_len, |
90 | callback_arg); |
91 | break; |
92 | |
93 | default: |
94 | return VPD_FAIL; |
95 | } |
96 | |
97 | return VPD_OK; |
98 | } |
99 | |