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 
vpd_decode_len(const u32 max_len,const u8 * in,u32 * length,u32 * decoded_len)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 
vpd_decode_entry(const u32 max_len,const u8 * input_buf,u32 * _consumed,const u8 ** entry,u32 * entry_len)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 - consumed, &input_buf[consumed],
43 			   entry_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 
vpd_decode_string(const u32 max_len,const u8 * input_buf,u32 * consumed,vpd_decode_callback callback,void * callback_arg)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, &key,
81 				     &key_len) != VPD_OK)
82 			return VPD_FAIL;
83 
84 		if (vpd_decode_entry(max_len, input_buf, consumed, &value,
85 				     &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