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+/*-
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+ * Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
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+ *
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+ * Licensed under the Apache License 2.0 (the "License"). You may not use
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+ * this file except in compliance with the License. You can obtain a copy
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+ * in the file LICENSE in the source distribution or at
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+ * https://www.openssl.org/source/license.html
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+ */
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+
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+/*
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+ * An example that uses the EVP_PKEY*, EVP_DigestSign* and EVP_DigestVerify*
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+ * methods to calculate public/private DSA keypair and to sign and verify
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+ * two static buffers.
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+ */
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+
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+#include <string.h>
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+#include <stdio.h>
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+#include <openssl/err.h>
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+#include <openssl/evp.h>
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+#include <openssl/decoder.h>
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+#include <openssl/dsa.h>
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+
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+/*
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+ * This demonstration will calculate and verify a signature of data using
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+ * the soliloquy from Hamlet scene 1 act 3
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+ */
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+
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+static const char *hamlet_1 =
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+ "To be, or not to be, that is the question,\n"
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+ "Whether tis nobler in the minde to suffer\n"
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+ "The slings and arrowes of outragious fortune,\n"
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+ "Or to take Armes again in a sea of troubles,\n"
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+;
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+static const char *hamlet_2 =
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+ "And by opposing, end them, to die to sleep;\n"
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+ "No more, and by a sleep, to say we end\n"
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+ "The heart-ache, and the thousand natural shocks\n"
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+ "That flesh is heir to? tis a consumation\n"
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+;
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+
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+static const char ALG[] = "DSA";
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+static const char DIGEST[] = "SHA256";
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+static const int NUMBITS = 2048;
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+static const char * const PROPQUERY = NULL;
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+
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+static int generate_dsa_params(OSSL_LIB_CTX *libctx,
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+ EVP_PKEY **p_params)
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+{
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+ int result = 0;
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+
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+ EVP_PKEY_CTX *pkey_ctx = NULL;
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+ EVP_PKEY *params = NULL;
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+
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+ pkey_ctx = EVP_PKEY_CTX_new_from_name(libctx, ALG, PROPQUERY);
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+ if (pkey_ctx == NULL)
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+ goto end;
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+
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+ if (EVP_PKEY_paramgen_init(pkey_ctx) <= 0)
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+ goto end;
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+
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+ if (EVP_PKEY_CTX_set_dsa_paramgen_bits(pkey_ctx, NUMBITS) <= 0)
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+ goto end;
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+ if (EVP_PKEY_paramgen(pkey_ctx, ¶ms) <= 0)
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+ goto end;
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+ if (params == NULL)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ if(result != 1) {
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+ EVP_PKEY_free(params);
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+ params = NULL;
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+ }
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+ EVP_PKEY_CTX_free(pkey_ctx);
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+ *p_params = params;
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+ fprintf(stdout, "Params:\n");
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+ EVP_PKEY_print_params_fp(stdout, params, 4, NULL);
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+ fprintf(stdout, "\n");
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+
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+ return result;
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+}
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+
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+static int generate_dsa_key(OSSL_LIB_CTX *libctx,
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+ EVP_PKEY *params,
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+ EVP_PKEY **p_pkey)
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+{
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+ int result = 0;
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+
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+ EVP_PKEY_CTX *ctx = NULL;
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+ EVP_PKEY *pkey = NULL;
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+
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+ ctx = EVP_PKEY_CTX_new_from_pkey(libctx, params,
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+ NULL);
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+ if (ctx == NULL)
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+ goto end;
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+ if (EVP_PKEY_keygen_init(ctx) <= 0)
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+ goto end;
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+
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+ if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
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+ goto end;
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+ if (pkey == NULL)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ if(result != 1) {
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+ EVP_PKEY_free(pkey);
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+ pkey = NULL;
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+ }
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+ EVP_PKEY_CTX_free(ctx);
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+ *p_pkey = pkey;
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+ fprintf(stdout, "Generating public/private key pair:\n");
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+ EVP_PKEY_print_public_fp(stdout, pkey, 4, NULL);
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+ fprintf(stdout, "\n");
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+ EVP_PKEY_print_private_fp(stdout, pkey, 4, NULL);
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+ fprintf(stdout, "\n");
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+ EVP_PKEY_print_params_fp(stdout, pkey, 4, NULL);
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+ fprintf(stdout, "\n");
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+
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+ return result;
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+}
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+
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+static int extract_public_key(const EVP_PKEY *pkey,
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+ OSSL_PARAM **p_public_key)
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+{
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+ int result = 0;
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+ OSSL_PARAM *public_key = NULL;
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+
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+ if (EVP_PKEY_todata(pkey, EVP_PKEY_PUBLIC_KEY, &public_key) != 1)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ if (result != 1) {
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+ OSSL_PARAM_free(public_key);
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+ public_key = NULL;
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+ }
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+ *p_public_key = public_key;
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+
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+ return result;
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+}
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+
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+static int extract_keypair(const EVP_PKEY *pkey,
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+ OSSL_PARAM **p_keypair)
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+{
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+ int result = 0;
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+ OSSL_PARAM *keypair = NULL;
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+
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+ if (EVP_PKEY_todata(pkey, EVP_PKEY_KEYPAIR, &keypair) != 1)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ if (result != 1) {
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+ OSSL_PARAM_free(keypair);
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+ keypair = NULL;
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+ }
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+ *p_keypair = keypair;
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+
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+ return result;
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+}
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+
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+static int demo_sign(OSSL_LIB_CTX *libctx,
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+ size_t *p_sig_len, unsigned char **p_sig_value,
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+ OSSL_PARAM keypair[])
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+{
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+ int result = 0;
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+ size_t sig_len = 0;
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+ unsigned char *sig_value = NULL;
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+ EVP_MD_CTX *ctx = NULL;
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+ EVP_PKEY_CTX *pkey_ctx = NULL;
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+ EVP_PKEY *pkey = NULL;
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+
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+ pkey_ctx = EVP_PKEY_CTX_new_from_name(libctx, ALG, PROPQUERY);
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+ if (pkey_ctx == NULL)
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+ goto end;
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+ if (EVP_PKEY_fromdata_init(pkey_ctx) != 1)
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+ goto end;
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+ if (EVP_PKEY_fromdata(pkey_ctx, &pkey, EVP_PKEY_KEYPAIR, keypair) != 1)
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+ goto end;
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+
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+ ctx = EVP_MD_CTX_create();
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+ if (ctx == NULL)
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+ goto end;
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+
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+ if (EVP_DigestSignInit_ex(ctx, NULL, DIGEST, libctx, NULL, pkey, NULL) != 1)
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+ goto end;
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+
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+ if (EVP_DigestSignUpdate(ctx, hamlet_1, sizeof(hamlet_1)) != 1)
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+ goto end;
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+
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+ if (EVP_DigestSignUpdate(ctx, hamlet_2, sizeof(hamlet_2)) != 1)
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+ goto end;
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+
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+ /* Calculate the signature size */
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+ if (EVP_DigestSignFinal(ctx, NULL, &sig_len) != 1)
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+ goto end;
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+ if (sig_len == 0)
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+ goto end;
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+
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+ sig_value = OPENSSL_malloc(sig_len);
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+ if (sig_value == NULL)
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+ goto end;
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+
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+ /* Calculate the signature */
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+ if (EVP_DigestSignFinal(ctx, sig_value, &sig_len) != 1)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ EVP_MD_CTX_free(ctx);
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+ if (result != 1) {
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+ OPENSSL_free(sig_value);
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+ sig_len = 0;
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+ sig_value = NULL;
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+ }
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+ *p_sig_len = sig_len;
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+ *p_sig_value = sig_value;
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+ EVP_PKEY_free(pkey);
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+ EVP_PKEY_CTX_free(pkey_ctx);
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+
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+ fprintf(stdout, "Generating signature:\n");
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+ BIO_dump_indent_fp(stdout, sig_value, sig_len, 2);
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+ fprintf(stdout, "\n");
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+ return result;
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+}
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+
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+static int demo_verify(OSSL_LIB_CTX *libctx,
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+ size_t sig_len, unsigned char *sig_value,
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+ OSSL_PARAM public_key[])
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+{
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+ int result = 0;
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+ EVP_MD_CTX *ctx = NULL;
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+ EVP_PKEY_CTX *pkey_ctx = NULL;
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+ EVP_PKEY *pkey = NULL;
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+
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+ pkey_ctx = EVP_PKEY_CTX_new_from_name(libctx, ALG, PROPQUERY);
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+ if (pkey_ctx == NULL)
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+ goto end;
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+ if (EVP_PKEY_fromdata_init(pkey_ctx) != 1)
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+ goto end;
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+ if (EVP_PKEY_fromdata(pkey_ctx, &pkey, EVP_PKEY_PUBLIC_KEY, public_key) != 1)
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+ goto end;
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+
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+ ctx = EVP_MD_CTX_create();
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+ if(ctx == NULL)
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+ goto end;
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+
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+ if (EVP_DigestVerifyInit_ex(ctx, NULL, DIGEST, libctx, NULL, pkey, NULL) != 1)
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+ goto end;
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+
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+ if (EVP_DigestVerifyUpdate(ctx, hamlet_1, sizeof(hamlet_1)) != 1)
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+ goto end;
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+
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+ if (EVP_DigestVerifyUpdate(ctx, hamlet_2, sizeof(hamlet_2)) != 1)
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+ goto end;
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+
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+ if (EVP_DigestVerifyFinal(ctx, sig_value, sig_len) != 1)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ EVP_PKEY_free(pkey);
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+ EVP_PKEY_CTX_free(pkey_ctx);
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+ EVP_MD_CTX_free(ctx);
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+ return result;
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+}
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+
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+int main(void)
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+{
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+ int result = 0;
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+ OSSL_LIB_CTX *libctx = NULL;
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+ EVP_PKEY *params = NULL;
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+ EVP_PKEY *pkey = NULL;
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+ OSSL_PARAM *public_key = NULL;
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+ OSSL_PARAM *keypair = NULL;
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+ size_t sig_len = 0;
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+ unsigned char *sig_value = NULL;
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+
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+ libctx = OSSL_LIB_CTX_new();
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+ if (libctx == NULL)
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+ goto end;
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+
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+ if (generate_dsa_params(libctx, ¶ms) != 1)
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+ goto end;
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+
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+ if (generate_dsa_key(libctx, params, &pkey) != 1)
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+ goto end;
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+
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+ if (extract_public_key(pkey, &public_key) != 1)
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+ goto end;
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+
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+ if (extract_keypair(pkey, &keypair) != 1)
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+ goto end;
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+
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+ /* The signer signs with his private key, and distributes his public key */
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+ if (demo_sign(libctx, &sig_len, &sig_value, keypair) != 1)
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+ goto end;
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+
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+ /* A verifier uses the signers public key to verify the signature */
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+ if (demo_verify(libctx, sig_len, sig_value, public_key) != 1)
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+ goto end;
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+
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+ result = 1;
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+end:
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+ if (result != 1)
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+ ERR_print_errors_fp(stderr);
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+
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+ OPENSSL_free(sig_value);
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+ EVP_PKEY_free(params);
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+ EVP_PKEY_free(pkey);
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+ OSSL_PARAM_free(public_key);
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+ OSSL_PARAM_free(keypair);
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+ OSSL_LIB_CTX_free(libctx);
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+
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+ return result ? 0 : 1;
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+}
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