Add support for TLS1.3 secret generation
authorMatt Caswell <matt@openssl.org>
Tue, 8 Nov 2016 10:34:28 +0000 (10:34 +0000)
committerMatt Caswell <matt@openssl.org>
Wed, 9 Nov 2016 14:08:14 +0000 (14:08 +0000)
Nothing is using this yet, it just adds the underlying functions necesary
for generating the TLS1.3 secrets.

Reviewed-by: Rich Salz <rsalz@openssl.org>
ssl/build.info
ssl/ssl_locl.h
ssl/tls13_enc.c [new file with mode: 0644]

index c7d4574..72b8dfc 100644 (file)
@@ -3,7 +3,7 @@ SOURCE[../libssl]=\
         pqueue.c packet.c \
         statem/statem_srvr.c statem/statem_clnt.c  s3_lib.c  s3_enc.c record/rec_layer_s3.c \
         statem/statem_lib.c s3_cbc.c s3_msg.c \
-        methods.c   t1_lib.c  t1_enc.c t1_ext.c \
+        methods.c   t1_lib.c  t1_enc.c tls13_enc.c t1_ext.c \
         d1_lib.c  record/rec_layer_d1.c d1_msg.c \
         statem/statem_dtls.c d1_srtp.c \
         ssl_lib.c ssl_cert.c ssl_sess.c \
index dcc2336..0c7aeed 100644 (file)
@@ -944,6 +944,12 @@ struct ssl_st {
      * be 'copied' into these ones
      */
     uint32_t mac_flags;
+    /*
+     * The TLS1.3 early_secret and handshake_secret. The master_secret is stored
+     * in the session.
+     */
+    unsigned char early_secret[EVP_MAX_MD_SIZE];
+    unsigned char handshake_secret[EVP_MAX_MD_SIZE];
     EVP_CIPHER_CTX *enc_read_ctx; /* cryptographic state */
     EVP_MD_CTX *read_hash;      /* used for mac generation */
     COMP_CTX *compress;         /* compression */
@@ -2004,6 +2010,21 @@ __owur size_t tls1_final_finish_mac(SSL *s, const char *str, size_t slen,
 __owur int tls1_generate_master_secret(SSL *s, unsigned char *out,
                                        unsigned char *p, size_t len,
                                        size_t *secret_size);
+__owur int tls13_derive_secret(SSL *s, const unsigned char *insecret,
+                               const unsigned char *label, size_t labellen,
+                               unsigned char *secret);
+__owur int tls13_derive_key(SSL *s, const unsigned char *secret,
+                            unsigned char *key, size_t keylen);
+__owur int tls13_derive_iv(SSL *s, const unsigned char *secret,
+                           unsigned char *iv, size_t ivlen);
+__owur int tls13_generate_early_secret(SSL *s, const unsigned char *insecret,
+                                       size_t insecretlen);
+__owur int tls13_generate_handshake_secret(SSL *s,
+                                           const unsigned char *insecret,
+                                           size_t insecretlen);
+__owur int tls13_generate_master_secret(SSL *s, unsigned char *out,
+                                        unsigned char *prev, size_t prevlen,
+                                        size_t *secret_size);
 __owur int tls1_export_keying_material(SSL *s, unsigned char *out, size_t olen,
                                        const char *label, size_t llen,
                                        const unsigned char *p, size_t plen,
diff --git a/ssl/tls13_enc.c b/ssl/tls13_enc.c
new file mode 100644 (file)
index 0000000..0ac54bb
--- /dev/null
@@ -0,0 +1,217 @@
+/*
+ * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (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 <stdlib.h>
+#include "ssl_locl.h"
+#include <openssl/evp.h>
+#include <openssl/kdf.h>
+
+#define TLS13_MAX_LABEL_LEN     246
+
+/* Always filled with zeros */
+static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
+
+const unsigned char keylabel[] = "key";
+const unsigned char ivlabel[] = "iv";
+
+/*
+ * Given a |secret|; a |label| of length |labellen|; and a |hash| of the
+ * handshake messages, derive a new secret |outlen| bytes long and store it in
+ * the location pointed to be |out|. The |hash| value may be NULL.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+static int tls13_hkdf_expand(SSL *s, const unsigned char *secret,
+                             const unsigned char *label, size_t labellen,
+                             const unsigned char *hash,
+                             unsigned char *out, size_t outlen)
+{
+    const unsigned char label_prefix[] = "TLS 1.3, ";
+    const EVP_MD *md = ssl_handshake_md(s);
+    EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
+    int ret;
+    size_t hkdflabellen;
+    size_t hashlen;
+    /*
+     * 2 bytes for length of whole HkdfLabel + 1 byte for length of combined
+     * prefix and label + bytes for the label itself + bytes for the hash
+     */
+    unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
+                            + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN
+                            + EVP_MAX_MD_SIZE];
+    WPACKET pkt;
+
+    if (pctx == NULL)
+        return 0;
+
+    hashlen = EVP_MD_size(md);
+
+    if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
+            || !WPACKET_put_bytes_u16(&pkt, outlen)
+            || !WPACKET_start_sub_packet_u8(&pkt)
+            || !WPACKET_memcpy(&pkt, label_prefix, sizeof(label_prefix) - 1)
+            || !WPACKET_memcpy(&pkt, label, labellen)
+            || !WPACKET_close(&pkt)
+            || !WPACKET_sub_memcpy_u8(&pkt, hash, (hash == NULL) ? 0 : hashlen)
+            || !WPACKET_get_total_written(&pkt, &hkdflabellen)
+            || !WPACKET_finish(&pkt)) {
+        WPACKET_cleanup(&pkt);
+        return 0;
+    }
+
+    ret = EVP_PKEY_derive_init(pctx) <= 0
+            || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY)
+               <= 0
+            || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
+            || EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, hashlen) <= 0
+            || EVP_PKEY_CTX_add1_hkdf_info(pctx, hkdflabel, hkdflabellen) <= 0
+            || EVP_PKEY_derive(pctx, out, &outlen) <= 0;
+
+    EVP_PKEY_CTX_free(pctx);
+
+    return ret == 0;
+}
+
+/*
+ * Given a input secret |insecret| and a |label| of length |labellen|, derive a
+ * new |secret|. This will be the length of the current hash output size and
+ * will be based on the current state of the handshake hashes.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+int tls13_derive_secret(SSL *s, const unsigned char *insecret,
+                        const unsigned char *label, size_t labellen,
+                        unsigned char *secret)
+{
+    unsigned char hash[EVP_MAX_MD_SIZE];
+    size_t hashlen;
+
+    if (!ssl3_digest_cached_records(s, 1))
+        return 0;
+
+    if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen))
+        return 0;
+
+    return tls13_hkdf_expand(s, insecret, label, labellen, hash, secret,
+                             hashlen);
+}
+
+/*
+ * Given a |secret| generate a |key| of length |keylen| bytes.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+int tls13_derive_key(SSL *s, const unsigned char *secret, unsigned char *key,
+                     size_t keylen)
+{
+    return tls13_hkdf_expand(s, secret, keylabel, sizeof(keylabel) - 1, NULL,
+                             key, keylen);
+}
+
+/*
+ * Given a |secret| generate an |iv| of length |ivlen| bytes.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+int tls13_derive_iv(SSL *s, const unsigned char *secret, unsigned char *iv,
+                    size_t ivlen)
+{
+    return tls13_hkdf_expand(s, secret, ivlabel, sizeof(ivlabel) - 1, NULL,
+                             iv, ivlen);
+}
+
+/*
+ * Given the previous secret |prevsecret| and a new input secret |insecret| of
+ * length |insecretlen|, generate a new secret and store it in the location
+ * pointed to by |outsecret|.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+static int tls13_generate_secret(SSL *s, const unsigned char *prevsecret,
+                                 const unsigned char *insecret,
+                                 size_t insecretlen,
+                                 unsigned char *outsecret)
+{
+    const EVP_MD *md = ssl_handshake_md(s);
+    size_t mdlen, prevsecretlen;
+    int ret;
+    EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
+
+    if (pctx == NULL)
+        return 0;
+
+    mdlen = EVP_MD_size(md);
+
+    if (insecret == NULL) {
+        insecret = default_zeros;
+        insecretlen = mdlen;
+    }
+    if (prevsecret == NULL) {
+        prevsecret = default_zeros;
+        prevsecretlen = 0;
+    } else {
+        prevsecretlen = mdlen;
+    }
+
+    ret = EVP_PKEY_derive_init(pctx) <= 0
+            || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY)
+               <= 0
+            || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
+            || EVP_PKEY_CTX_set1_hkdf_key(pctx, insecret, insecretlen) <= 0
+            || EVP_PKEY_CTX_set1_hkdf_salt(pctx, prevsecret, prevsecretlen)
+               <= 0
+            || EVP_PKEY_derive(pctx, outsecret, &mdlen)
+               <= 0;
+
+    EVP_PKEY_CTX_free(pctx);
+    return ret == 0;
+}
+
+/*
+ * Given an input secret |insecret| of length |insecretlen| generate the early
+ * secret.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+int tls13_generate_early_secret(SSL *s, const unsigned char *insecret,
+                                size_t insecretlen)
+{
+    return tls13_generate_secret(s, NULL, insecret, insecretlen,
+                                 (unsigned char *)&s->early_secret);
+}
+
+/*
+ * Given an input secret |insecret| of length |insecretlen| generate the
+ * handshake secret. This requires the early secret to already have been
+ * generated.
+ *
+ * Returns 1 on success  0 on failure.
+ */
+int tls13_generate_handshake_secret(SSL *s, const unsigned char *insecret,
+                                size_t insecretlen)
+{
+    return tls13_generate_secret(s, s->early_secret, insecret, insecretlen,
+                                 (unsigned char *)&s->handshake_secret);
+}
+
+/*
+ * Given the handshake secret |prev| of length |prevlen| generate the master
+ * secret and store its length in |*secret_size|
+ *
+ * Returns 1 on success  0 on failure.
+ */
+int tls13_generate_master_secret(SSL *s, unsigned char *out,
+                                 unsigned char *prev, size_t prevlen,
+                                 size_t *secret_size)
+{
+    *secret_size = EVP_MD_size(ssl_handshake_md(s));
+    return tls13_generate_secret(s, prev, NULL, 0, out);
+}
+
+