diff options
author | Hugo Landau <hlandau@openssl.org> | 2022-03-03 08:20:05 +0000 |
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committer | Tomas Mraz <tomas@openssl.org> | 2022-03-04 16:12:17 +0100 |
commit | 6269e6923f137870ab9a678ae91f10daed517ec5 (patch) | |
tree | f67d4e9d58372aea3b25071573f6aea98ebd215d /demos | |
parent | e0de19409716ec6723d20e31b93cf92df24797fd (diff) |
EVP demo for XOF digest using SHAKE256
This demo optionally accepts a single command line argument, allowing
the output length to be specified.
Fixes #14106.
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17803)
(cherry picked from commit 4c8cdcd1cf74747a80b4f7dd323cd83ea6c985d8)
Diffstat (limited to 'demos')
-rw-r--r-- | demos/README.txt | 1 | ||||
-rw-r--r-- | demos/digest/EVP_MD_xof.c | 132 | ||||
-rw-r--r-- | demos/digest/Makefile | 7 |
3 files changed, 137 insertions, 3 deletions
diff --git a/demos/README.txt b/demos/README.txt index 291094bf9d..3632e11a84 100644 --- a/demos/README.txt +++ b/demos/README.txt @@ -16,6 +16,7 @@ cms: digest: EVP_MD_demo.c Compute a digest from multiple buffers EVP_MD_stdin.c Compute a digest with data read from stdin +EVP_MD_xof.c Compute a digest using the SHAKE256 XOF EVP_f_md.c Compute a digest using BIO and EVP_f_md kdf: diff --git a/demos/digest/EVP_MD_xof.c b/demos/digest/EVP_MD_xof.c new file mode 100644 index 0000000000..f31c047164 --- /dev/null +++ b/demos/digest/EVP_MD_xof.c @@ -0,0 +1,132 @@ +/*- + * 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 <string.h> +#include <openssl/err.h> +#include <openssl/evp.h> +#include <openssl/core_names.h> + +/* + * Example of using an extendable-output hash function (XOF). A XOF is a hash + * function with configurable output length and which can generate an + * arbitrarily large output. + * + * This example uses SHAKE256, an extendable output variant of SHA3 (Keccak). + * + * To generate different output lengths, you can pass a single integer argument + * on the command line, which is the output size in bytes. By default, a 20-byte + * output is generated and (for this length only) a known answer test is + * performed. + */ + +/* Our input to the XOF hash function. */ +const char message[] = "This is a test message."; + +/* Expected output when an output length of 20 bytes is used. */ +static const char known_answer[] = { + 0x52, 0x97, 0x93, 0x78, 0x27, 0x58, 0x7d, 0x62, + 0x8b, 0x00, 0x25, 0xb5, 0xec, 0x39, 0x5e, 0x2d, + 0x7f, 0x3e, 0xd4, 0x19 +}; + +/* + * A property query used for selecting the SHAKE256 implementation. + */ +static const char *propq = NULL; + +int main(int argc, char **argv) +{ + int rv = 1; + OSSL_LIB_CTX *libctx = NULL; + EVP_MD *md = NULL; + EVP_MD_CTX *ctx = NULL; + unsigned int digest_len = 20; + int digest_len_i; + unsigned char *digest = NULL; + + /* Allow digest length to be changed for demonstration purposes. */ + if (argc > 1) { + digest_len_i = atoi(argv[1]); + if (digest_len_i <= 0) { + fprintf(stderr, "Specify a non-negative digest length\n"); + goto end; + } + + digest_len = (unsigned int)digest_len_i; + } + + /* + * Retrieve desired algorithm. This must be a hash algorithm which supports + * XOF. + */ + md = EVP_MD_fetch(libctx, "SHAKE256", propq); + if (md == NULL) { + fprintf(stderr, "Failed to retrieve SHAKE256 algorithm\n"); + goto end; + } + + /* Create context. */ + ctx = EVP_MD_CTX_new(); + if (ctx == NULL) { + fprintf(stderr, "Failed to create digest context\n"); + goto end; + } + + /* Initialize digest context. */ + if (EVP_DigestInit(ctx, md) == 0) { + fprintf(stderr, "Failed to initialize digest\n"); + goto end; + } + + /* + * Feed our message into the digest function. + * This may be called multiple times. + */ + if (EVP_DigestUpdate(ctx, message, sizeof(message)) == 0) { + fprintf(stderr, "Failed to hash input message\n"); + goto end; + } + + /* Allocate enough memory for our digest length. */ + digest = OPENSSL_malloc(digest_len); + if (digest == NULL) { + fprintf(stderr, "Failed to allocate memory for digest\n"); + goto end; + } + + /* Get computed digest. The digest will be of whatever length we specify. */ + if (EVP_DigestFinalXOF(ctx, digest, digest_len) == 0) { + fprintf(stderr, "Failed to finalize hash\n"); + goto end; + } + + printf("Output digest:\n"); + BIO_dump_indent_fp(stdout, digest, digest_len, 2); + + /* If digest length is 20 bytes, check it matches our known answer. */ + if (digest_len == 20) { + /* + * Always use a constant-time function such as CRYPTO_memcmp + * when comparing cryptographic values. Do not use memcmp(3). + */ + if (CRYPTO_memcmp(digest, known_answer, sizeof(known_answer)) != 0) { + fprintf(stderr, "Output does not match expected result\n"); + goto end; + } + } + + rv = 0; +end: + OPENSSL_free(digest); + EVP_MD_CTX_free(ctx); + EVP_MD_free(md); + OSSL_LIB_CTX_free(libctx); + return rv; +} diff --git a/demos/digest/Makefile b/demos/digest/Makefile index bcd4c4353b..0bfb6dd5f0 100644 --- a/demos/digest/Makefile +++ b/demos/digest/Makefile @@ -3,20 +3,21 @@ # # LD_LIBRARY_PATH=../.. ./EVP_MD_demo -CFLAGS = -I../../include -g +CFLAGS = -I../../include -g -Wall LDFLAGS = -L../.. LDLIBS = -lcrypto -all: EVP_MD_demo EVP_MD_stdin BIO_f_md +all: EVP_MD_demo EVP_MD_stdin EVP_MD_xof BIO_f_md %.o: %.c $(CC) $(CFLAGS) -c $< EVP_MD_demo: EVP_MD_demo.o EVP_MD_stdin: EVP_MD_stdin.o +EVP_MD_xof: EVP_MD_xof.o BIO_f_md: BIO_f_md.o test: ; clean: - $(RM) *.o EVP_MD_demo EVP_MD_stdin BIO_f_md + $(RM) *.o EVP_MD_demo EVP_MD_stdin EVP_MD_xof BIO_f_md |