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/*
* Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#include <stdlib.h>
#include <openssl/core_names.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/params.h>
#include <openssl/err.h>
#include <openssl/bio.h>
#include "rsa_pss.h"
/* The data to be signed. This will be hashed. */
static const char test_message[] =
"This is an example message to be signed.";
/* A property query used for selecting algorithm implementations. */
static const char *propq = NULL;
/*
* This function demonstrates RSA signing of an arbitrary-length message.
* Hashing is performed automatically. In this example, SHA-256 is used. If you
* have already hashed your message and simply want to sign the hash directly,
* see rsa_pss_direct.c.
*/
static int sign(OSSL_LIB_CTX *libctx, unsigned char **sig, size_t *sig_len)
{
int ret = 0;
EVP_PKEY *pkey = NULL;
EVP_MD_CTX *mctx = NULL;
OSSL_PARAM params[2], *p = params;
const unsigned char *ppriv_key = NULL;
*sig = NULL;
/* Load DER-encoded RSA private key. */
ppriv_key = rsa_priv_key;
pkey = d2i_PrivateKey_ex(EVP_PKEY_RSA, NULL, &ppriv_key,
sizeof(rsa_priv_key), libctx, propq);
if (pkey == NULL) {
fprintf(stderr, "Failed to load private key\n");
goto end;
}
/* Create MD context used for signing. */
mctx = EVP_MD_CTX_new();
if (mctx == NULL) {
fprintf(stderr, "Failed to create MD context\n");
goto end;
}
/* Initialize MD context for signing. */
*p++ = OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_PAD_MODE,
OSSL_PKEY_RSA_PAD_MODE_PSS, 0);
*p = OSSL_PARAM_construct_end();
if (EVP_DigestSignInit_ex(mctx, NULL, "SHA256", libctx, propq,
pkey, params) == 0) {
fprintf(stderr, "Failed to initialize signing context\n");
goto end;
}
/*
* Feed data to be signed into the algorithm. This may
* be called multiple times.
*/
if (EVP_DigestSignUpdate(mctx, test_message, sizeof(test_message)) == 0) {
fprintf(stderr, "Failed to hash message into signing context\n");
goto end;
}
/* Determine signature length. */
if (EVP_DigestSignFinal(mctx, NULL, sig_len) == 0) {
fprintf(stderr, "Failed to get signature length\n");
goto end;
}
/* Allocate memory for signature. */
*sig = OPENSSL_malloc(*sig_len);
if (*sig == NULL) {
fprintf(stderr, "Failed to allocate memory for signature\n");
goto end;
}
/* Generate signature. */
if (EVP_DigestSignFinal(mctx, *sig, sig_len) == 0) {
fprintf(stderr, "Failed to sign\n");
goto end;
}
ret = 1;
end:
EVP_MD_CTX_free(mctx);
EVP_PKEY_free(pkey);
if (ret == 0)
OPENSSL_free(*sig);
return ret;
}
/*
* This function demonstrates verification of an RSA signature over an
* arbitrary-length message using the PSS signature scheme. Hashing is performed
* automatically.
*/
static int verify(OSSL_LIB_CTX *libctx, const unsigned char *sig, size_t sig_len)
{
int ret = 0;
EVP_PKEY *pkey = NULL;
EVP_MD_CTX *mctx = NULL;
OSSL_PARAM params[2], *p = params;
const unsigned char *ppub_key = NULL;
/* Load DER-encoded RSA public key. */
ppub_key = rsa_pub_key;
pkey = d2i_PublicKey(EVP_PKEY_RSA, NULL, &ppub_key, sizeof(rsa_pub_key));
if (pkey == NULL) {
fprintf(stderr, "Failed to load public key\n");
goto end;
}
/* Create MD context used for verification. */
mctx = EVP_MD_CTX_new();
if (mctx == NULL) {
fprintf(stderr, "Failed to create MD context\n");
goto end;
}
/* Initialize MD context for verification. */
*p++ = OSSL_PARAM_construct_utf8_string(OSSL_SIGNATURE_PARAM_PAD_MODE,
OSSL_PKEY_RSA_PAD_MODE_PSS, 0);
*p = OSSL_PARAM_construct_end();
if (EVP_DigestVerifyInit_ex(mctx, NULL, "SHA256", libctx, propq,
pkey, params) == 0) {
fprintf(stderr, "Failed to initialize signing context\n");
goto end;
}
/*
* Feed data to be signed into the algorithm. This may
* be called multiple times.
*/
if (EVP_DigestVerifyUpdate(mctx, test_message, sizeof(test_message)) == 0) {
fprintf(stderr, "Failed to hash message into signing context\n");
goto end;
}
/* Verify signature. */
if (EVP_DigestVerifyFinal(mctx, sig, sig_len) == 0) {
fprintf(stderr, "Failed to verify signature; "
"signature may be invalid\n");
goto end;
}
ret = 1;
end:
EVP_MD_CTX_free(mctx);
EVP_PKEY_free(pkey);
return ret;
}
int main(int argc, char **argv)
{
int ret = EXIT_FAILURE;
OSSL_LIB_CTX *libctx = NULL;
unsigned char *sig = NULL;
size_t sig_len = 0;
if (sign(libctx, &sig, &sig_len) == 0)
goto end;
if (verify(libctx, sig, sig_len) == 0)
goto end;
ret = EXIT_SUCCESS;
end:
OPENSSL_free(sig);
OSSL_LIB_CTX_free(libctx);
return ret;
}
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