1/*
2 * Copyright 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 <stdio.h>
11#include <stdlib.h>
12#include <openssl/core_names.h>
13#include <openssl/evp.h>
14#include <openssl/rsa.h>
15#include <openssl/params.h>
16#include <openssl/err.h>
17#include <openssl/bio.h>
18#include "rsa_pss.h"
19
20/*
21 * The digest to be signed. This should be the output of a hash function.
22 * Here we sign an all-zeroes digest for demonstration purposes.
23 */
24static const unsigned char test_digest[32] = {0};
25
26/* A property query used for selecting algorithm implementations. */
27static const char *propq = NULL;
28
29/*
30 * This function demonstrates RSA signing of a SHA-256 digest using the PSS
31 * padding scheme. You must already have hashed the data you want to sign.
32 * For a higher-level demonstration which does the hashing for you, see
33 * rsa_pss_hash.c.
34 *
35 * For more information, see RFC 8017 section 9.1. The digest passed in
36 * (test_digest above) corresponds to the 'mHash' value.
37 */
38static int sign(OSSL_LIB_CTX *libctx, unsigned char **sig, size_t *sig_len)
39{
40    int rv = 0;
41    EVP_PKEY *pkey = NULL;
42    EVP_PKEY_CTX *ctx = NULL;
43    EVP_MD *md = NULL;
44    const unsigned char *ppriv_key = NULL;
45
46    *sig = NULL;
47
48    /* Load DER-encoded RSA private key. */
49    ppriv_key = rsa_priv_key;
50    pkey = d2i_PrivateKey_ex(EVP_PKEY_RSA, NULL, &ppriv_key,
51                             sizeof(rsa_priv_key), libctx, propq);
52    if (pkey == NULL) {
53        fprintf(stderr, "Failed to load private key\n");
54        goto end;
55    }
56
57    /* Fetch hash algorithm we want to use. */
58    md = EVP_MD_fetch(libctx, "SHA256", propq);
59    if (md == NULL) {
60        fprintf(stderr, "Failed to fetch hash algorithm\n");
61        goto end;
62    }
63
64    /* Create signing context. */
65    ctx = EVP_PKEY_CTX_new_from_pkey(libctx, pkey, propq);
66    if (ctx == NULL) {
67        fprintf(stderr, "Failed to create signing context\n");
68        goto end;
69    }
70
71    /* Initialize context for signing and set options. */
72    if (EVP_PKEY_sign_init(ctx) == 0) {
73        fprintf(stderr, "Failed to initialize signing context\n");
74        goto end;
75    }
76
77    if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PSS_PADDING) == 0) {
78        fprintf(stderr, "Failed to configure padding\n");
79        goto end;
80    }
81
82    if (EVP_PKEY_CTX_set_signature_md(ctx, md) == 0) {
83        fprintf(stderr, "Failed to configure digest type\n");
84        goto end;
85    }
86
87    /* Determine length of signature. */
88    if (EVP_PKEY_sign(ctx, NULL, sig_len,
89                      test_digest, sizeof(test_digest)) == 0) {
90        fprintf(stderr, "Failed to get signature length\n");
91        goto end;
92    }
93
94    /* Allocate memory for signature. */
95    *sig = OPENSSL_malloc(*sig_len);
96    if (*sig == NULL) {
97        fprintf(stderr, "Failed to allocate memory for signature\n");
98        goto end;
99    }
100
101    /* Generate signature. */
102    if (EVP_PKEY_sign(ctx, *sig, sig_len,
103                      test_digest, sizeof(test_digest)) != 1) {
104        fprintf(stderr, "Failed to sign\n");
105        goto end;
106    }
107
108    rv = 1;
109end:
110    EVP_PKEY_CTX_free(ctx);
111    EVP_PKEY_free(pkey);
112    EVP_MD_free(md);
113
114    if (rv == 0)
115        OPENSSL_free(*sig);
116
117    return rv;
118}
119
120/*
121 * This function demonstrates verification of an RSA signature over a SHA-256
122 * digest using the PSS signature scheme.
123 */
124static int verify(OSSL_LIB_CTX *libctx, const unsigned char *sig, size_t sig_len)
125{
126    int rv = 0;
127    const unsigned char *ppub_key = NULL;
128    EVP_PKEY *pkey = NULL;
129    EVP_PKEY_CTX *ctx = NULL;
130    EVP_MD *md = NULL;
131
132    /* Load DER-encoded RSA public key. */
133    ppub_key = rsa_pub_key;
134    pkey = d2i_PublicKey(EVP_PKEY_RSA, NULL, &ppub_key, sizeof(rsa_pub_key));
135    if (pkey == NULL) {
136        fprintf(stderr, "Failed to load public key\n");
137        goto end;
138    }
139
140    /* Fetch hash algorithm we want to use. */
141    md = EVP_MD_fetch(libctx, "SHA256", propq);
142    if (md == NULL) {
143        fprintf(stderr, "Failed to fetch hash algorithm\n");
144        goto end;
145    }
146
147    /* Create verification context. */
148    ctx = EVP_PKEY_CTX_new_from_pkey(libctx, pkey, propq);
149    if (ctx == NULL) {
150        fprintf(stderr, "Failed to create verification context\n");
151        goto end;
152    }
153
154    /* Initialize context for verification and set options. */
155    if (EVP_PKEY_verify_init(ctx) == 0) {
156        fprintf(stderr, "Failed to initialize verification context\n");
157        goto end;
158    }
159
160    if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PSS_PADDING) == 0) {
161        fprintf(stderr, "Failed to configure padding\n");
162        goto end;
163    }
164
165    if (EVP_PKEY_CTX_set_signature_md(ctx, md) == 0) {
166        fprintf(stderr, "Failed to configure digest type\n");
167        goto end;
168    }
169
170    /* Verify signature. */
171    if (EVP_PKEY_verify(ctx, sig, sig_len,
172                        test_digest, sizeof(test_digest)) == 0) {
173        fprintf(stderr, "Failed to verify signature; "
174                "signature may be invalid\n");
175        goto end;
176    }
177
178    rv = 1;
179end:
180    EVP_PKEY_CTX_free(ctx);
181    EVP_PKEY_free(pkey);
182    EVP_MD_free(md);
183    return rv;
184}
185
186int main(int argc, char **argv)
187{
188    int rv = 1;
189    OSSL_LIB_CTX *libctx = NULL;
190    unsigned char *sig = NULL;
191    size_t sig_len = 0;
192
193    if (sign(libctx, &sig, &sig_len) == 0)
194        goto end;
195
196    if (verify(libctx, sig, sig_len) == 0)
197        goto end;
198
199    rv = 0;
200end:
201    OPENSSL_free(sig);
202    OSSL_LIB_CTX_free(libctx);
203    return rv;
204}
205