GH355: Implement HKDF

This patch implements the HMAC-based Extract-and-Expand Key Derivation
Function (HKDF) as defined in RFC 5869.

It is required to implement the QUIC and TLS 1.3 protocols (among others).

Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Dr. Stephen Henson <steve@openssl.org>

3 files changed, 335 insertions, 3 deletions

diff --git a/crypto/kdf/Makefile.in b/crypto/kdf/Makefile.in
index 44d57622e0..a1e9584435 100644
--- a/crypto/kdf/Makefile.in
+++ b/crypto/kdf/Makefile.in
@@ -15,8 +15,8 @@ CFLAGS= $(INCLUDES) $(CFLAG) $(SHARED_CFLAG)
 GENERAL=Makefile
 
 LIB=$(TOP)/libcrypto.a
-LIBSRC=tls1_prf.c kdf_err.c
-LIBOBJ=tls1_prf.o kdf_err.o
+LIBSRC=tls1_prf.c kdf_err.c hkdf.c
+LIBOBJ=tls1_prf.o kdf_err.o hkdf.o
 
 SRC= $(LIBSRC)
 
diff --git a/crypto/kdf/build.info b/crypto/kdf/build.info
index 320f534055..cbe2080ed7 100644
--- a/crypto/kdf/build.info
+++ b/crypto/kdf/build.info
@@ -1,3 +1,3 @@
 LIBS=../../libcrypto
 SOURCE[../../libcrypto]=\
-        tls1_prf.c kdf_err.c
+        tls1_prf.c kdf_err.c hkdf.c
diff --git a/crypto/kdf/hkdf.c b/crypto/kdf/hkdf.c
new file mode 100644
index 0000000000..bbe4334fa5
--- /dev/null
+++ b/crypto/kdf/hkdf.c
@@ -0,0 +1,332 @@
+/* ====================================================================
+ * Copyright (c) 2016 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <openssl/hmac.h>
+#include <openssl/kdf.h>
+#include <openssl/evp.h>
+#include "internal/cryptlib.h"
+#include "internal/evp_int.h"
+
+#define HKDF_MAXBUF 1024
+
+static unsigned char *HKDF(const EVP_MD *evp_md,
+                           const unsigned char *salt, size_t salt_len,
+                           const unsigned char *key, size_t key_len,
+                           const unsigned char *info, size_t info_len,
+                           unsigned char *okm, size_t okm_len);
+
+static unsigned char *HKDF_Extract(const EVP_MD *evp_md,
+                                   const unsigned char *salt, size_t salt_len,
+                                   const unsigned char *key, size_t key_len,
+                                   unsigned char *prk, size_t *prk_len);
+
+static unsigned char *HKDF_Expand(const EVP_MD *evp_md,
+                                  const unsigned char *prk, size_t prk_len,
+                                  const unsigned char *info, size_t info_len,
+                                  unsigned char *okm, size_t okm_len);
+
+typedef struct {
+    const EVP_MD *md;
+    unsigned char *salt;
+    size_t salt_len;
+    unsigned char *key;
+    size_t key_len;
+    unsigned char info[HKDF_MAXBUF];
+    size_t info_len;
+} HKDF_PKEY_CTX;
+
+static int pkey_hkdf_init(EVP_PKEY_CTX *ctx)
+{
+    HKDF_PKEY_CTX *kctx;
+
+    kctx = OPENSSL_zalloc(sizeof(*kctx));
+    if (kctx == NULL)
+        return 0;
+
+    ctx->data = kctx;
+
+    return 1;
+}
+
+static void pkey_hkdf_cleanup(EVP_PKEY_CTX *ctx)
+{
+    HKDF_PKEY_CTX *kctx = ctx->data;
+    OPENSSL_clear_free(kctx->salt, kctx->salt_len);
+    OPENSSL_clear_free(kctx->key, kctx->key_len);
+    OPENSSL_cleanse(kctx->info, kctx->info_len);
+    OPENSSL_free(kctx);
+}
+
+static int pkey_hkdf_ctrl(EVP_PKEY_CTX *ctx, int type, int p1, void *p2)
+{
+    HKDF_PKEY_CTX *kctx = ctx->data;
+
+    switch (type) {
+    case EVP_PKEY_CTRL_HKDF_MD:
+        if (p2 == NULL)
+            return 0;
+
+        kctx->md = p2;
+        return 1;
+
+    case EVP_PKEY_CTRL_HKDF_SALT:
+        if (p1 == 0 || p2 == NULL)
+            return 1;
+
+        if (p1 < 0)
+            return 0;
+
+        if (kctx->salt != NULL)
+            OPENSSL_clear_free(kctx->salt, kctx->salt_len);
+
+        kctx->salt = OPENSSL_memdup(p2, p1);
+        if (kctx->salt == NULL)
+            return 0;
+
+        kctx->salt_len = p1;
+        return 1;
+
+    case EVP_PKEY_CTRL_HKDF_KEY:
+        if (p1 < 0)
+            return 0;
+
+        if (kctx->key != NULL)
+            OPENSSL_clear_free(kctx->key, kctx->key_len);
+
+        kctx->key = OPENSSL_memdup(p2, p1);
+        if (kctx->key == NULL)
+            return 0;
+
+        kctx->key_len  = p1;
+        return 1;
+
+    case EVP_PKEY_CTRL_HKDF_INFO:
+        if (p1 == 0 || p2 == NULL)
+            return 1;
+
+        if (p1 < 0 || p1 > (int)(HKDF_MAXBUF - kctx->info_len))
+            return 0;
+
+        memcpy(kctx->info + kctx->info_len, p2, p1);
+        kctx->info_len += p1;
+        return 1;
+
+    default:
+        return -2;
+
+    }
+}
+
+static int pkey_hkdf_ctrl_str(EVP_PKEY_CTX *ctx, const char *type,
+                              const char *value)
+{
+    if (strcmp(type, "md") == 0)
+        return EVP_PKEY_CTX_set_hkdf_md(ctx, EVP_get_digestbyname(value));
+
+    if (strcmp(type, "salt") == 0)
+        return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);
+
+    if (strcmp(type, "hexsalt") == 0)
+        return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);
+
+    if (strcmp(type, "key") == 0)
+        return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);
+
+    if (strcmp(type, "hexkey") == 0)
+        return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);
+
+    if (strcmp(type, "info") == 0)
+        return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);
+
+    if (strcmp(type, "hexinfo") == 0)
+        return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);
+
+    return -2;
+}
+
+static int pkey_hkdf_derive(EVP_PKEY_CTX *ctx, unsigned char *key,
+                            size_t *keylen)
+{
+    HKDF_PKEY_CTX *kctx = ctx->data;
+
+    if (kctx->md == NULL || kctx->key == NULL)
+        return 0;
+
+    if (HKDF(kctx->md, kctx->salt, kctx->salt_len, kctx->key, kctx->key_len,
+             kctx->info, kctx->info_len, key, *keylen) == NULL)
+    {
+        return 0;
+    }
+
+    return 1;
+}
+
+const EVP_PKEY_METHOD hkdf_pkey_meth = {
+    EVP_PKEY_HKDF,
+    0,
+    pkey_hkdf_init,
+    0,
+    pkey_hkdf_cleanup,
+
+    0, 0,
+    0, 0,
+
+    0,
+    0,
+
+    0,
+    0,
+
+    0, 0,
+
+    0, 0, 0, 0,
+
+    0, 0,
+
+    0, 0,
+
+    0,
+    pkey_hkdf_derive,
+    pkey_hkdf_ctrl,
+    pkey_hkdf_ctrl_str
+};
+
+static unsigned char *HKDF(const EVP_MD *evp_md,
+                           const unsigned char *salt, size_t salt_len,
+                           const unsigned char *key, size_t key_len,
+                           const unsigned char *info, size_t info_len,
+                           unsigned char *okm, size_t okm_len)
+{
+    unsigned char prk[EVP_MAX_MD_SIZE];
+    size_t prk_len;
+
+    if (!HKDF_Extract(evp_md, salt, salt_len, key, key_len, prk, &prk_len))
+        return NULL;
+
+    return HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
+}
+
+static unsigned char *HKDF_Extract(const EVP_MD *evp_md,
+                                   const unsigned char *salt, size_t salt_len,
+                                   const unsigned char *key, size_t key_len,
+                                   unsigned char *prk, size_t *prk_len)
+{
+    unsigned int tmp_len;
+
+    if (!HMAC(evp_md, salt, salt_len, key, key_len, prk, &tmp_len))
+        return NULL;
+
+    *prk_len = tmp_len;
+    return prk;
+}
+
+static unsigned char *HKDF_Expand(const EVP_MD *evp_md,
+                                  const unsigned char *prk, size_t prk_len,
+                                  const unsigned char *info, size_t info_len,
+                                  unsigned char *okm, size_t okm_len)
+{
+    HMAC_CTX *hmac;
+
+    unsigned int i;
+
+    unsigned char prev[EVP_MAX_MD_SIZE];
+
+    size_t done_len = 0, dig_len = EVP_MD_size(evp_md);
+
+    size_t n = okm_len / dig_len;
+    if (okm_len % dig_len)
+        n++;
+
+    if (n > 255)
+        return NULL;
+
+    if ((hmac = HMAC_CTX_new()) == NULL)
+        return NULL;
+
+    if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
+        goto err;
+
+    for (i = 1; i <= n; i++) {
+        size_t copy_len;
+        const unsigned char ctr = i;
+
+        if (i > 1) {
+            if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
+                goto err;
+
+            if (!HMAC_Update(hmac, prev, dig_len))
+                goto err;
+        }
+
+        if (!HMAC_Update(hmac, info, info_len))
+            goto err;
+
+        if (!HMAC_Update(hmac, &ctr, 1))
+            goto err;
+
+        if (!HMAC_Final(hmac, prev, NULL))
+            goto err;
+
+        copy_len = (done_len + dig_len > okm_len) ?
+                       okm_len - done_len :
+                       dig_len;
+
+        memcpy(okm + done_len, prev, copy_len);
+
+        done_len += copy_len;
+    }
+
+    HMAC_CTX_free(hmac);
+    return okm;
+
+ err:
+    HMAC_CTX_free(hmac);
+    return NULL;
+}