1/*
2 * Copyright 2020-2022 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#include <stdlib.h>
11#include <string.h>
12#include "internal/cryptlib.h"
13#include "internal/der.h"
14#include "crypto/bn.h"
15
16static int int_start_context(WPACKET *pkt, int tag)
17{
18    if (tag < 0)
19        return 1;
20    if (!ossl_assert(tag <= 30))
21        return 0;
22    return WPACKET_start_sub_packet(pkt);
23}
24
25static int int_end_context(WPACKET *pkt, int tag)
26{
27    /*
28     * If someone set the flag WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH on this
29     * sub-packet and this sub-packet has nothing written to it, the DER length
30     * will not be written, and the total written size will be unchanged before
31     * and after WPACKET_close().  We use size1 and size2 to determine if
32     * anything was written, and only write our tag if it has.
33     *
34     */
35    size_t size1, size2;
36
37    if (tag < 0)
38        return 1;
39    if (!ossl_assert(tag <= 30))
40        return 0;
41
42    /* Context specific are normally (?) constructed */
43    tag |= DER_F_CONSTRUCTED | DER_C_CONTEXT;
44
45    return WPACKET_get_total_written(pkt, &size1)
46        && WPACKET_close(pkt)
47        && WPACKET_get_total_written(pkt, &size2)
48        && (size1 == size2 || WPACKET_put_bytes_u8(pkt, tag));
49}
50
51int ossl_DER_w_precompiled(WPACKET *pkt, int tag,
52                           const unsigned char *precompiled,
53                           size_t precompiled_n)
54{
55    return int_start_context(pkt, tag)
56        && WPACKET_memcpy(pkt, precompiled, precompiled_n)
57        && int_end_context(pkt, tag);
58}
59
60int ossl_DER_w_boolean(WPACKET *pkt, int tag, int b)
61{
62    return int_start_context(pkt, tag)
63        && WPACKET_start_sub_packet(pkt)
64        && (!b || WPACKET_put_bytes_u8(pkt, 0xFF))
65        && !WPACKET_close(pkt)
66        && !WPACKET_put_bytes_u8(pkt, DER_P_BOOLEAN)
67        && int_end_context(pkt, tag);
68}
69
70int ossl_DER_w_octet_string(WPACKET *pkt, int tag,
71                            const unsigned char *data, size_t data_n)
72{
73    return int_start_context(pkt, tag)
74        && WPACKET_start_sub_packet(pkt)
75        && WPACKET_memcpy(pkt, data, data_n)
76        && WPACKET_close(pkt)
77        && WPACKET_put_bytes_u8(pkt, DER_P_OCTET_STRING)
78        && int_end_context(pkt, tag);
79}
80
81int ossl_DER_w_octet_string_uint32(WPACKET *pkt, int tag, uint32_t value)
82{
83    unsigned char tmp[4] = { 0, 0, 0, 0 };
84    unsigned char *pbuf = tmp + (sizeof(tmp) - 1);
85
86    while (value > 0) {
87        *pbuf-- = (value & 0xFF);
88        value >>= 8;
89    }
90    return ossl_DER_w_octet_string(pkt, tag, tmp, sizeof(tmp));
91}
92
93static int int_der_w_integer(WPACKET *pkt, int tag,
94                             int (*put_bytes)(WPACKET *pkt, const void *v,
95                                              unsigned int *top_byte),
96                             const void *v)
97{
98    unsigned int top_byte = 0;
99
100    return int_start_context(pkt, tag)
101        && WPACKET_start_sub_packet(pkt)
102        && put_bytes(pkt, v, &top_byte)
103        && ((top_byte & 0x80) == 0 || WPACKET_put_bytes_u8(pkt, 0))
104        && WPACKET_close(pkt)
105        && WPACKET_put_bytes_u8(pkt, DER_P_INTEGER)
106        && int_end_context(pkt, tag);
107}
108
109static int int_put_bytes_uint32(WPACKET *pkt, const void *v,
110                               unsigned int *top_byte)
111{
112    const uint32_t *value = v;
113    uint32_t tmp = *value;
114    size_t n = 0;
115
116    while (tmp != 0) {
117        n++;
118        *top_byte = (tmp & 0xFF);
119        tmp >>= 8;
120    }
121    if (n == 0)
122        n = 1;
123
124    return WPACKET_put_bytes__(pkt, *value, n);
125}
126
127/* For integers, we only support unsigned values for now */
128int ossl_DER_w_uint32(WPACKET *pkt, int tag, uint32_t v)
129{
130    return int_der_w_integer(pkt, tag, int_put_bytes_uint32, &v);
131}
132
133static int int_put_bytes_bn(WPACKET *pkt, const void *v,
134                            unsigned int *top_byte)
135{
136    unsigned char *p = NULL;
137    size_t n = BN_num_bytes(v);
138
139    /* The BIGNUM limbs are in LE order */
140    *top_byte =
141        ((bn_get_words(v) [(n - 1) / BN_BYTES]) >> (8 * ((n - 1) % BN_BYTES)))
142        & 0xFF;
143
144    if (!WPACKET_allocate_bytes(pkt, n, &p))
145        return 0;
146    if (p != NULL)
147        BN_bn2bin(v, p);
148    return 1;
149}
150
151int ossl_DER_w_bn(WPACKET *pkt, int tag, const BIGNUM *v)
152{
153    if (v == NULL || BN_is_negative(v))
154        return 0;
155    if (BN_is_zero(v))
156        return ossl_DER_w_uint32(pkt, tag, 0);
157
158    return int_der_w_integer(pkt, tag, int_put_bytes_bn, v);
159}
160
161int ossl_DER_w_null(WPACKET *pkt, int tag)
162{
163    return int_start_context(pkt, tag)
164        && WPACKET_start_sub_packet(pkt)
165        && WPACKET_close(pkt)
166        && WPACKET_put_bytes_u8(pkt, DER_P_NULL)
167        && int_end_context(pkt, tag);
168}
169
170/* Constructed things need a start and an end */
171int ossl_DER_w_begin_sequence(WPACKET *pkt, int tag)
172{
173    return int_start_context(pkt, tag)
174        && WPACKET_start_sub_packet(pkt);
175}
176
177int ossl_DER_w_end_sequence(WPACKET *pkt, int tag)
178{
179    /*
180     * If someone set the flag WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH on this
181     * sub-packet and this sub-packet has nothing written to it, the DER length
182     * will not be written, and the total written size will be unchanged before
183     * and after WPACKET_close().  We use size1 and size2 to determine if
184     * anything was written, and only write our tag if it has.
185     *
186     * Because we know that int_end_context() needs to do the same check,
187     * we reproduce this flag if the written length was unchanged, or we will
188     * have an erroneous context tag.
189     */
190    size_t size1, size2;
191
192    return WPACKET_get_total_written(pkt, &size1)
193        && WPACKET_close(pkt)
194        && WPACKET_get_total_written(pkt, &size2)
195        && (size1 == size2
196            ? WPACKET_set_flags(pkt, WPACKET_FLAGS_ABANDON_ON_ZERO_LENGTH)
197            : WPACKET_put_bytes_u8(pkt, DER_F_CONSTRUCTED | DER_P_SEQUENCE))
198        && int_end_context(pkt, tag);
199}
200