1 /*
2 * Copyright 2005-2024 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10 /*
11 * RSA low level APIs are deprecated for public use, but still ok for
12 * internal use.
13 */
14 #include "internal/deprecated.h"
15
16 #include <stdio.h>
17 #include "internal/cryptlib.h"
18 #include <openssl/bn.h>
19 #include <openssl/rsa.h>
20 #include <openssl/objects.h>
21
22 /*
23 * X9.31 Embeds the hash inside the following data structure
24 *
25 * header (4 bits = 0x6)
26 * padding (consisting of zero or more 4 bit values of a sequence of 0xB,
27 * ending with the terminator 0xA)
28 * hash(Msg) hash of a message (the output size is related to the hash function)
29 * trailer (consists of 2 bytes)
30 * The 1st byte is related to a part number for a hash algorithm
31 * (See RSA_X931_hash_id()), followed by the fixed value 0xCC
32 *
33 * The RSA modulus size n (which for X9.31 is 1024 + 256*s) is the size of the data
34 * structure, which determines the padding size.
35 * i.e. len(padding) = n - len(header) - len(hash) - len(trailer)
36 *
37 * Params:
38 * to The output buffer to write the data structure to.
39 * tolen The size of 'to' in bytes (it is the size of the n)
40 * from The input hash followed by the 1st byte of the trailer.
41 * flen The size of the input hash + 1 (trailer byte)
42 */
RSA_padding_add_X931(unsigned char * to,int tlen,const unsigned char * from,int flen)43 int RSA_padding_add_X931(unsigned char *to, int tlen,
44 const unsigned char *from, int flen)
45 {
46 int j;
47 unsigned char *p;
48
49 /*
50 * We need at least 1 byte for header + padding (0x6A)
51 * And 2 trailer bytes (but we subtract 1 since flen includes 1 trailer byte)
52 */
53 j = tlen - flen - 2;
54
55 if (j < 0) {
56 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
57 return -1;
58 }
59
60 p = (unsigned char *)to;
61
62 /* If no padding start and end nibbles are in one byte */
63 if (j == 0) {
64 *p++ = 0x6A;
65 } else {
66 *p++ = 0x6B;
67 if (j > 1) {
68 memset(p, 0xBB, j - 1);
69 p += j - 1;
70 }
71 *p++ = 0xBA;
72 }
73 memcpy(p, from, (unsigned int)flen);
74 p += flen;
75 *p = 0xCC;
76 return 1;
77 }
78
RSA_padding_check_X931(unsigned char * to,int tlen,const unsigned char * from,int flen,int num)79 int RSA_padding_check_X931(unsigned char *to, int tlen,
80 const unsigned char *from, int flen, int num)
81 {
82 int i = 0, j;
83 const unsigned char *p;
84
85 p = from;
86 if ((num != flen) || ((*p != 0x6A) && (*p != 0x6B))) {
87 ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_HEADER);
88 return -1;
89 }
90
91 if (*p++ == 0x6B) {
92 j = flen - 3;
93 for (i = 0; i < j; i++) {
94 unsigned char c = *p++;
95 if (c == 0xBA)
96 break;
97 if (c != 0xBB) {
98 ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_PADDING);
99 return -1;
100 }
101 }
102
103 j -= i;
104
105 if (i == 0) {
106 ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_PADDING);
107 return -1;
108 }
109
110 } else {
111 j = flen - 2;
112 }
113
114 if (p[j] != 0xCC) {
115 ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_TRAILER);
116 return -1;
117 }
118
119 memcpy(to, p, (unsigned int)j);
120
121 return j;
122 }
123
124 /*
125 * Translate between X9.31 hash ids and NIDs
126 * The returned values relate to ISO/IEC 10118 part numbers which consist of
127 * a hash algorithm and hash number. The returned values are used as the
128 * first byte of the 'trailer'.
129 */
130
RSA_X931_hash_id(int nid)131 int RSA_X931_hash_id(int nid)
132 {
133 switch (nid) {
134 case NID_sha1:
135 return 0x33;
136
137 case NID_sha256:
138 return 0x34;
139
140 case NID_sha384:
141 return 0x36;
142
143 case NID_sha512:
144 return 0x35;
145
146 }
147 return -1;
148 }
149
