1/*
2 *  Copyright(C) 2006 Cameron Rich
3 *
4 *  This library is free software; you can redistribute it and/or modify
5 *  it under the terms of the GNU Lesser General Public License as published by
6 *  the Free Software Foundation; either version 2.1 of the License, or
7 *  (at your option) any later version.
8 *
9 *  This library is distributed in the hope that it will be useful,
10 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
11 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 *  GNU Lesser General Public License for more details.
13 *
14 *  You should have received a copy of the GNU Lesser General Public License
15 *  along with this library; if not, write to the Free Software
16 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17 */
18
19/**
20 * Implements the RSA public encryption algorithm. Uses the bigint library to
21 * perform its calculations.
22 */
23
24#include <stdio.h>
25#include <string.h>
26#include <time.h>
27#include <stdlib.h>
28#include "crypto.h"
29
30#ifdef CONFIG_BIGINT_CRT
31static bigint *bi_crt(const RSA_CTX *rsa, bigint *bi);
32#endif
33
34void RSA_priv_key_new(RSA_CTX **ctx,
35        const uint8_t *modulus, int mod_len,
36        const uint8_t *pub_exp, int pub_len,
37        const uint8_t *priv_exp, int priv_len
38#if CONFIG_BIGINT_CRT
39      , const uint8_t *p, int p_len,
40        const uint8_t *q, int q_len,
41        const uint8_t *dP, int dP_len,
42        const uint8_t *dQ, int dQ_len,
43        const uint8_t *qInv, int qInv_len
44#endif
45    )
46{
47    RSA_CTX *rsa_ctx;
48    BI_CTX *bi_ctx;
49    RSA_pub_key_new(ctx, modulus, mod_len, pub_exp, pub_len);
50    rsa_ctx = *ctx;
51    bi_ctx = rsa_ctx->bi_ctx;
52    rsa_ctx->d = bi_import(bi_ctx, priv_exp, priv_len);
53    bi_permanent(rsa_ctx->d);
54
55#ifdef CONFIG_BIGINT_CRT
56    rsa_ctx->p = bi_import(bi_ctx, p, p_len);
57    rsa_ctx->q = bi_import(bi_ctx, q, q_len);
58    rsa_ctx->dP = bi_import(bi_ctx, dP, dP_len);
59    rsa_ctx->dQ = bi_import(bi_ctx, dQ, dQ_len);
60    rsa_ctx->qInv = bi_import(bi_ctx, qInv, qInv_len);
61    bi_permanent(rsa_ctx->dP);
62    bi_permanent(rsa_ctx->dQ);
63    bi_permanent(rsa_ctx->qInv);
64    bi_set_mod(bi_ctx, rsa_ctx->p, BIGINT_P_OFFSET);
65    bi_set_mod(bi_ctx, rsa_ctx->q, BIGINT_Q_OFFSET);
66#endif
67}
68
69void RSA_pub_key_new(RSA_CTX **ctx,
70        const uint8_t *modulus, int mod_len,
71        const uint8_t *pub_exp, int pub_len)
72{
73    RSA_CTX *rsa_ctx;
74    BI_CTX *bi_ctx = bi_initialize();
75    *ctx = (RSA_CTX *)calloc(1, sizeof(RSA_CTX));
76    rsa_ctx = *ctx;
77    rsa_ctx->bi_ctx = bi_ctx;
78    rsa_ctx->num_octets = (mod_len & 0xFFF0);
79    rsa_ctx->m = bi_import(bi_ctx, modulus, mod_len);
80    bi_set_mod(bi_ctx, rsa_ctx->m, BIGINT_M_OFFSET);
81    rsa_ctx->e = bi_import(bi_ctx, pub_exp, pub_len);
82    bi_permanent(rsa_ctx->e);
83}
84
85/**
86 * Free up any RSA context resources.
87 */
88void RSA_free(RSA_CTX *rsa_ctx)
89{
90    BI_CTX *bi_ctx;
91    if (rsa_ctx == NULL)                /* deal with ptrs that are null */
92        return;
93
94    bi_ctx = rsa_ctx->bi_ctx;
95
96    bi_depermanent(rsa_ctx->e);
97    bi_free(bi_ctx, rsa_ctx->e);
98    bi_free_mod(rsa_ctx->bi_ctx, BIGINT_M_OFFSET);
99
100    if (rsa_ctx->d)
101    {
102        bi_depermanent(rsa_ctx->d);
103        bi_free(bi_ctx, rsa_ctx->d);
104#ifdef CONFIG_BIGINT_CRT
105        bi_depermanent(rsa_ctx->dP);
106        bi_depermanent(rsa_ctx->dQ);
107        bi_depermanent(rsa_ctx->qInv);
108        bi_free(bi_ctx, rsa_ctx->dP);
109        bi_free(bi_ctx, rsa_ctx->dQ);
110        bi_free(bi_ctx, rsa_ctx->qInv);
111        bi_free_mod(rsa_ctx->bi_ctx, BIGINT_P_OFFSET);
112        bi_free_mod(rsa_ctx->bi_ctx, BIGINT_Q_OFFSET);
113#endif
114    }
115
116    bi_terminate(bi_ctx);
117    free(rsa_ctx);
118}
119
120/**
121 * @brief Use PKCS1.5 for decryption/verification.
122 * @param ctx [in] The context
123 * @param in_data [in] The data to encrypt (must be < modulus size-11)
124 * @param out_data [out] The encrypted data.
125 * @param is_decryption [in] Decryption or verify operation.
126 * @return  The number of bytes that were originally encrypted. -1 on error.
127 * @see http://www.rsasecurity.com/rsalabs/node.asp?id=2125
128 */
129int RSA_decrypt(const RSA_CTX *ctx, const uint8_t *in_data,
130                            uint8_t *out_data, int is_decryption)
131{
132    int byte_size = ctx->num_octets;
133    uint8_t *block;
134    int i, size;
135    bigint *decrypted_bi, *dat_bi;
136
137    memset(out_data, 0, byte_size); /* initialise */
138
139    /* decrypt */
140    dat_bi = bi_import(ctx->bi_ctx, in_data, byte_size);
141#ifdef CONFIG_SSL_CERT_VERIFICATION
142    decrypted_bi = is_decryption ?  /* decrypt or verify? */
143            RSA_private(ctx, dat_bi) : RSA_public(ctx, dat_bi);
144#else   /* always a decryption */
145    decrypted_bi = RSA_private(ctx, dat_bi);
146#endif
147
148    /* convert to a normal block */
149    block = (uint8_t *)malloc(byte_size);
150    bi_export(ctx->bi_ctx, decrypted_bi, block, byte_size);
151
152    i = 10; /* start at the first possible non-padded byte */
153
154#ifdef CONFIG_SSL_CERT_VERIFICATION
155    if (is_decryption == 0) /* PKCS1.5 signing pads with "0xff"s */
156    {
157        while (block[i++] == 0xff && i < byte_size);
158
159        if (block[i-2] != 0xff)
160            i = byte_size;     /*ensure size is 0 */
161    }
162    else                    /* PKCS1.5 encryption padding is random */
163#endif
164    {
165        while (block[i++] && i < byte_size);
166    }
167    size = byte_size - i;
168
169    /* get only the bit we want */
170    if (size > 0)
171        memcpy(out_data, &block[i], size);
172
173    free(block);
174    return size ? size : -1;
175}
176
177/**
178 * Performs m = c^d mod n
179 */
180bigint *RSA_private(const RSA_CTX *c, bigint *bi_msg)
181{
182#ifdef CONFIG_BIGINT_CRT
183    return bi_crt(c, bi_msg);
184#else
185    BI_CTX *ctx = c->bi_ctx;
186    ctx->mod_offset = BIGINT_M_OFFSET;
187    return bi_mod_power(ctx, bi_msg, c->d);
188#endif
189}
190
191#ifdef CONFIG_BIGINT_CRT
192/**
193 * Use the Chinese Remainder Theorem to quickly perform RSA decrypts.
194 * This should really be in bigint.c (and was at one stage), but needs
195 * access to the RSA_CTX context...
196 */
197static bigint *bi_crt(const RSA_CTX *rsa, bigint *bi)
198{
199    BI_CTX *ctx = rsa->bi_ctx;
200    bigint *m1, *m2, *h;
201
202    /* Montgomery has a condition the 0 < x, y < m and these products violate
203     * that condition. So disable Montgomery when using CRT */
204#if defined(CONFIG_BIGINT_MONTGOMERY)
205    ctx->use_classical = 1;
206#endif
207    ctx->mod_offset = BIGINT_P_OFFSET;
208    m1 = bi_mod_power(ctx, bi_copy(bi), rsa->dP);
209
210    ctx->mod_offset = BIGINT_Q_OFFSET;
211    m2 = bi_mod_power(ctx, bi, rsa->dQ);
212
213    h = bi_subtract(ctx, bi_add(ctx, m1, rsa->p), bi_copy(m2), NULL);
214    h = bi_multiply(ctx, h, rsa->qInv);
215    ctx->mod_offset = BIGINT_P_OFFSET;
216    h = bi_residue(ctx, h);
217#if defined(CONFIG_BIGINT_MONTGOMERY)
218    ctx->use_classical = 0;         /* reset for any further operation */
219#endif
220    return bi_add(ctx, m2, bi_multiply(ctx, rsa->q, h));
221}
222#endif
223
224#ifdef CONFIG_SSL_FULL_MODE
225/**
226 * Used for diagnostics.
227 */
228void RSA_print(const RSA_CTX *rsa_ctx)
229{
230    if (rsa_ctx == NULL)
231        return;
232
233    printf("-----------------   RSA DEBUG   ----------------\n");
234    printf("Size:\t%d\n", rsa_ctx->num_octets);
235    bi_print("Modulus", rsa_ctx->m);
236    bi_print("Public Key", rsa_ctx->e);
237    bi_print("Private Key", rsa_ctx->d);
238}
239#endif
240
241#ifdef CONFIG_SSL_CERT_VERIFICATION
242/**
243 * Performs c = m^e mod n
244 */
245bigint *RSA_public(const RSA_CTX * c, bigint *bi_msg)
246{
247    c->bi_ctx->mod_offset = BIGINT_M_OFFSET;
248    return bi_mod_power(c->bi_ctx, bi_msg, c->e);
249}
250
251/**
252 * Use PKCS1.5 for encryption/signing.
253 * see http://www.rsasecurity.com/rsalabs/node.asp?id=2125
254 */
255int RSA_encrypt(const RSA_CTX *ctx, const uint8_t *in_data, uint16_t in_len,
256        uint8_t *out_data, int is_signing)
257{
258    int byte_size = ctx->num_octets;
259    int num_pads_needed = byte_size-in_len-3;
260    bigint *dat_bi, *encrypt_bi;
261
262    /* note: in_len+11 must be > byte_size */
263    out_data[0] = 0;     /* ensure encryption block is < modulus */
264
265    if (is_signing)
266    {
267        out_data[1] = 1;        /* PKCS1.5 signing pads with "0xff"'s */
268        memset(&out_data[2], 0xff, num_pads_needed);
269    }
270    else /* randomize the encryption padding with non-zero bytes */
271    {
272        out_data[1] = 2;
273        get_random_NZ(num_pads_needed, &out_data[2]);
274    }
275
276    out_data[2+num_pads_needed] = 0;
277    memcpy(&out_data[3+num_pads_needed], in_data, in_len);
278
279    /* now encrypt it */
280    dat_bi = bi_import(ctx->bi_ctx, out_data, byte_size);
281    encrypt_bi = is_signing ? RSA_private(ctx, dat_bi) :
282        RSA_public(ctx, dat_bi);
283    bi_export(ctx->bi_ctx, encrypt_bi, out_data, byte_size);
284    return byte_size;
285}
286
287#if 0
288/**
289 * Take a signature and decrypt it.
290 */
291bigint *RSA_sign_verify(BI_CTX *ctx, const uint8_t *sig, int sig_len,
292        bigint *modulus, bigint *pub_exp)
293{
294    uint8_t *block;
295    int i, size;
296    bigint *decrypted_bi, *dat_bi;
297    bigint *bir = NULL;
298
299    block = (uint8_t *)malloc(sig_len);
300
301    /* decrypt */
302    dat_bi = bi_import(ctx, sig, sig_len);
303    ctx->mod_offset = BIGINT_M_OFFSET;
304
305    /* convert to a normal block */
306    decrypted_bi = bi_mod_power2(ctx, dat_bi, modulus, pub_exp);
307
308    bi_export(ctx, decrypted_bi, block, sig_len);
309    ctx->mod_offset = BIGINT_M_OFFSET;
310
311    i = 10; /* start at the first possible non-padded byte */
312    while (block[i++] && i < sig_len);
313    size = sig_len - i;
314
315    /* get only the bit we want */
316    if (size > 0)
317    {
318        int len;
319        const uint8_t *sig_ptr = x509_get_signature(&block[i], &len);
320
321        if (sig_ptr)
322        {
323            bir = bi_import(ctx, sig_ptr, len);
324        }
325    }
326
327    free(block);
328    return bir;
329}
330#endif
331
332#endif  /* CONFIG_SSL_CERT_VERIFICATION */
333