Add EVP demo for SIPHASH

Fixes #14121.

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/17793)

(cherry picked from commit 864853988e80517a563d2423d4fb742323995433)

2 files changed, 130 insertions, 0 deletions

diff --git a/demos/README.txt b/demos/README.txt
index a20e3a5536..dae5c881d2 100644
--- a/demos/README.txt
+++ b/demos/README.txt
@@ -28,6 +28,7 @@ scrypt.c               Demonstration of SCRYPT password based key derivation
 mac:
 gmac.c                 Demonstration of GMAC message authentication
 poly1305.c             Demonstration of Poly1305-AES message authentication
+siphash.c              Demonstration of SIPHASH message authentication
 
 pkey:
 EVP_PKEY_EC_keygen.c   Generate an EC key.
diff --git a/demos/mac/siphash.c b/demos/mac/siphash.c
new file mode 100644
index 0000000000..4d36a9d486
--- /dev/null
+++ b/demos/mac/siphash.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright 2021-2022 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/params.h>
+#include <openssl/err.h>
+
+/*
+ * Taken from the test vector from the paper "SipHash: a fast short-input PRF".
+ * https://www.aumasson.jp/siphash/siphash.pdf
+ */
+
+/*
+ * Hard coding the key into an application is very bad.
+ * It is done here solely for educational purposes.
+ */
+static unsigned char key[] = {
+    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
+};
+
+static unsigned char data[] = {
+    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e
+};
+
+static const unsigned char expected_output[] = {
+    0xe5, 0x45, 0xbe, 0x49, 0x61, 0xca, 0x29, 0xa1
+};
+
+/*
+ * A property query used for selecting the SIPHASH implementation.
+ */
+static char *propq = NULL;
+
+int main(int argc, char **argv)
+{
+    int rv = EXIT_FAILURE;
+    EVP_MAC *mac = NULL;
+    EVP_MAC_CTX *mctx = NULL;
+    unsigned char out[8];
+    OSSL_PARAM params[4], *p = params;
+    OSSL_LIB_CTX *library_context = NULL;
+    unsigned int digest_len = 8, c_rounds = 2, d_rounds = 4;
+    size_t out_len = 0;
+
+    library_context = OSSL_LIB_CTX_new();
+    if (library_context == NULL) {
+        fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
+        goto end;
+    }
+
+    /* Fetch the SipHash implementation */
+    mac = EVP_MAC_fetch(library_context, "SIPHASH", propq);
+    if (mac == NULL) {
+        fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
+        goto end;
+    }
+
+    /* Create a context for the SipHash operation */
+    mctx = EVP_MAC_CTX_new(mac);
+    if (mctx == NULL) {
+        fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
+        goto end;
+    }
+
+    /* SipHash can support either 8 or 16-byte digests. */
+    *p++ = OSSL_PARAM_construct_uint(OSSL_MAC_PARAM_SIZE, &digest_len);
+
+    /*
+     * The number of C-rounds and D-rounds is configurable. Standard SipHash
+     * uses values of 2 and 4 respectively. The following lines are unnecessary
+     * as they set the default, but demonstrate how to change these values.
+     */
+    *p++ = OSSL_PARAM_construct_uint(OSSL_MAC_PARAM_C_ROUNDS, &c_rounds);
+    *p++ = OSSL_PARAM_construct_uint(OSSL_MAC_PARAM_D_ROUNDS, &d_rounds);
+
+    *p = OSSL_PARAM_construct_end();
+
+    /* Initialise the SIPHASH operation */
+    if (!EVP_MAC_init(mctx, key, sizeof(key), params)) {
+        fprintf(stderr, "EVP_MAC_init() failed\n");
+        goto end;
+    }
+
+    /* Make one or more calls to process the data to be authenticated */
+    if (!EVP_MAC_update(mctx, data, sizeof(data))) {
+        fprintf(stderr, "EVP_MAC_update() failed\n");
+        goto end;
+    }
+
+    /* Make one call to the final to get the MAC */
+    if (!EVP_MAC_final(mctx, out, &out_len, sizeof(out))) {
+        fprintf(stderr, "EVP_MAC_final() failed\n");
+        goto end;
+    }
+
+    printf("Generated MAC:\n");
+    BIO_dump_indent_fp(stdout, out, out_len, 2);
+    putchar('\n');
+
+    if (out_len != sizeof(expected_output)) {
+        fprintf(stderr, "Generated MAC has an unexpected length\n");
+        goto end;
+    }
+
+    if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
+        fprintf(stderr, "Generated MAC does not match expected value\n");
+        goto end;
+    }
+
+    rv = EXIT_SUCCESS;
+end:
+    EVP_MAC_CTX_free(mctx);
+    EVP_MAC_free(mac);
+    OSSL_LIB_CTX_free(library_context);
+    if (rv != EXIT_SUCCESS)
+        ERR_print_errors_fp(stderr);
+    return rv;
+}