Move tls13_exporter() code.

It makes more sense to have tls13_exporter() in tls13_key_schedule.c,
rather than tls13_lib.c

ok tb@

1 files changed, 72 insertions, 1 deletions

diff --git a/src/lib/libssl/tls13_key_schedule.c b/src/lib/libssl/tls13_key_schedule.c
index 2c23be8d3e..abc35c4e83 100644
--- a/src/lib/libssl/tls13_key_schedule.c
+++ b/src/lib/libssl/tls13_key_schedule.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_key_schedule.c,v 1.16 2022/10/14 06:56:33 tb Exp $ */
+/* $OpenBSD: tls13_key_schedule.c,v 1.17 2022/11/07 11:53:39 jsing Exp $ */
 /*
  * Copyright (c) 2018, Bob Beck <beck@openbsd.org>
  *
@@ -21,6 +21,7 @@
 #include <openssl/hkdf.h>
 
 #include "bytestring.h"
+#include "ssl_locl.h"
 #include "tls13_internal.h"
 
 int
@@ -385,3 +386,73 @@ tls13_update_server_traffic_secret(struct tls13_secrets *secrets)
             secrets->digest, &secrets->server_application_traffic,
             "traffic upd", &context);
 }
+
+int
+tls13_exporter(struct tls13_ctx *ctx, const uint8_t *label, size_t label_len,
+    const uint8_t *context_value, size_t context_value_len, uint8_t *out,
+    size_t out_len)
+{
+        struct tls13_secret context, export_out, export_secret;
+        struct tls13_secrets *secrets = ctx->hs->tls13.secrets;
+        EVP_MD_CTX *md_ctx = NULL;
+        unsigned int md_out_len;
+        int md_len;
+        int ret = 0;
+
+        /*
+         * RFC 8446 Section 7.5.
+         */
+
+        memset(&context, 0, sizeof(context));
+        memset(&export_secret, 0, sizeof(export_secret));
+
+        export_out.data = out;
+        export_out.len = out_len;
+
+        if (!ctx->handshake_completed)
+                return 0;
+
+        md_len = EVP_MD_size(secrets->digest);
+        if (md_len <= 0 || md_len > EVP_MAX_MD_SIZE)
+                goto err;
+
+        if (!tls13_secret_init(&export_secret, md_len))
+                goto err;
+        if (!tls13_secret_init(&context, md_len))
+                goto err;
+
+        /* In TLSv1.3 no context is equivalent to an empty context. */
+        if (context_value == NULL) {
+                context_value = "";
+                context_value_len = 0;
+        }
+
+        if ((md_ctx = EVP_MD_CTX_new()) == NULL)
+                goto err;
+        if (!EVP_DigestInit_ex(md_ctx, secrets->digest, NULL))
+                goto err;
+        if (!EVP_DigestUpdate(md_ctx, context_value, context_value_len))
+                goto err;
+        if (!EVP_DigestFinal_ex(md_ctx, context.data, &md_out_len))
+                goto err;
+        if (md_len != md_out_len)
+                goto err;
+
+        if (!tls13_derive_secret_with_label_length(&export_secret,
+            secrets->digest, &secrets->exporter_master, label, label_len,
+            &secrets->empty_hash))
+                goto err;
+
+        if (!tls13_hkdf_expand_label(&export_out, secrets->digest,
+            &export_secret, "exporter", &context))
+                goto err;
+
+        ret = 1;
+
+ err:
+        EVP_MD_CTX_free(md_ctx);
+        tls13_secret_cleanup(&context);
+        tls13_secret_cleanup(&export_secret);
+
+        return ret;
+}