Add demo for HKDF

Fixes #14120

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15784)

3 files changed, 127 insertions, 0 deletions

diff --git a/demos/README.txt b/demos/README.txt
index 7472821c3b..cdcbd02f94 100644
--- a/demos/README.txt
+++ b/demos/README.txt
@@ -18,6 +18,9 @@ EVP_MD_demo.c          Compute a digest from multiple buffers
 EVP_MD_stdin.c         Compute a digest with data read from stdin
 EVP_f_md.c             Compute a digest using BIO and EVP_f_md
 
+kdf:
+hkdf.c                 Demonstration of HMAC based key derivation
+
 pkey:
 EVP_PKEY_EC_keygen.c   Generate an EC key.
 
diff --git a/demos/kdf/Makefile b/demos/kdf/Makefile
new file mode 100644
index 0000000000..b561de43b7
--- /dev/null
+++ b/demos/kdf/Makefile
@@ -0,0 +1,20 @@
+#
+# To run the demos when linked with a shared library (default):
+#
+#    LD_LIBRARY_PATH=../.. ./hkdf
+
+CFLAGS = -I../../include -g
+LDFLAGS = -L../..
+LDLIBS = -lcrypto
+
+all: hkdf
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c $<
+
+hkdf: hkdf.o
+
+test: ;
+
+clean:
+	$(RM) *.o hkdf
diff --git a/demos/kdf/hkdf.c b/demos/kdf/hkdf.c
new file mode 100644
index 0000000000..cb7a170e94
--- /dev/null
+++ b/demos/kdf/hkdf.c
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2021 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 <openssl/core_names.h>
+#include <openssl/crypto.h>
+#include <openssl/kdf.h>
+#include <openssl/obj_mac.h>
+#include <openssl/params.h>
+
+/*
+ * test vector from
+ * https://datatracker.ietf.org/doc/html/rfc5869
+ */
+
+static unsigned char hkdf_salt[] = {
+    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b,
+    0x0c
+};
+
+static unsigned char hkdf_ikm[] = {
+    0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
+    0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b
+};
+
+static unsigned char hkdf_info[] = {
+    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9
+};
+
+/* Expected output keying material */
+static unsigned char hkdf_okm[] = {
+    0x3c, 0xb2, 0x5f, 0x25, 0xfa, 0xac, 0xd5, 0x7a, 0x90, 0x43, 0x4f, 0x64,
+    0xd0, 0x36, 0x2f, 0x2a, 0x2d, 0x2d, 0x0a, 0x90, 0xcf, 0x1a, 0x5a, 0x4c,
+    0x5d, 0xb0, 0x2d, 0x56, 0xec, 0xc4, 0xc5, 0xbf, 0x34, 0x00, 0x72, 0x08,
+    0xd5, 0xb8, 0x87, 0x18, 0x58, 0x65
+};
+
+int main(int argc, char **argv)
+{
+    int rv = 1;
+    EVP_KDF *kdf = NULL;
+    EVP_KDF_CTX *kctx = NULL;
+    unsigned char out[42];
+    OSSL_PARAM params[5], *p = params;
+    OSSL_LIB_CTX *library_context = NULL;
+
+    library_context = OSSL_LIB_CTX_new();
+    if (library_context == NULL) {
+        fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
+        goto end;
+    }
+
+    /* Fetch the key derivation function implementation */
+    kdf = EVP_KDF_fetch(library_context, "HKDF", NULL);
+    if (kdf == NULL) {
+        fprintf(stderr, "EVP_KDF_fetch() returned NULL\n");
+        goto end;
+    }
+
+    /* Create a context for the key derivation operation */
+    kctx = EVP_KDF_CTX_new(kdf);
+    if (kctx == NULL) {
+        fprintf(stderr, "EVP_KDF_CTX_new() returned NULL\n");
+        goto end;
+    }
+
+    /* Set the underlying hash function used to derive the key */
+    *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
+                                            "SHA256", 0);
+    /* Set input keying material */
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY, hkdf_ikm,
+                                             sizeof(hkdf_ikm));
+    /* Set application specific information */
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, hkdf_info,
+                                             sizeof(hkdf_info));
+    /* Set salt */
+    *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, hkdf_salt,
+                                             sizeof(hkdf_salt));
+    *p = OSSL_PARAM_construct_end();
+
+    /* Derive the key */
+    if (EVP_KDF_derive(kctx, out, sizeof(out), params) != 1) {
+        fprintf(stderr, "EVP_KDF_derive() failed\n");
+        goto end;
+    }
+
+    if (CRYPTO_memcmp(hkdf_okm, out, sizeof(hkdf_okm)) != 0) {
+        fprintf(stderr, "Generated key does not match expected value\n");
+        goto end;
+    }
+
+    rv = 0;
+end:
+    EVP_KDF_CTX_free(kctx);
+    EVP_KDF_free(kdf);
+    OSSL_LIB_CTX_free(library_context);
+    return rv;
+}