Reduce stack usage in tls13_hkdf_expand

[openssl.git] / ssl / tls13_enc.c

diff --git a/ssl/tls13_enc.c b/ssl/tls13_enc.c
index 3fc8e96a899c864a5a1adc9d1146c926f5c1f9a4..b6825d20c2dc0bba5c199fef9c76dbbab8d88d35 100644 (file)
--- a/ssl/tls13_enc.c
+++ b/ssl/tls13_enc.c
@@ -13,7 +13,14 @@
 #include <openssl/evp.h>
 #include <openssl/kdf.h>
 
-#define TLS13_MAX_LABEL_LEN     246
+/*
+ * RFC 8446, 7.1 Key Schedule, says:
+ * Note: With common hash functions, any label longer than 12 characters
+ * requires an additional iteration of the hash function to compute.
+ * The labels in this specification have all been chosen to fit within
+ * this limit.
+ */
+#define TLS13_MAX_LABEL_LEN     12
 
 /* Always filled with zeros */
 static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
@@ -29,14 +36,15 @@ int tls13_hkdf_expand(SSL *s, const EVP_MD *md, const unsigned char *secret,
                              const unsigned char *data, size_t datalen,
                              unsigned char *out, size_t outlen)
 {
-    const unsigned char label_prefix[] = "tls13 ";
+    static const unsigned char label_prefix[] = "tls13 ";
     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
+     * 2 bytes for length of derived secret + 1 byte for length of combined
+     * prefix and label + bytes for the label itself + 1 byte length of hash
+     * + bytes for the hash itself
      */
     unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
                             + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN
@@ -271,6 +279,7 @@ size_t tls13_final_finish_mac(SSL *s, const char *str, size_t slen,
 
         key = EVP_PKEY_new_raw_private_key(EVP_PKEY_HMAC, NULL, finsecret,
                                            hashlen);
+        OPENSSL_cleanse(finsecret, sizeof(finsecret));
     }
 
     if (key == NULL
@@ -425,7 +434,7 @@ int tls13_change_cipher_state(SSL *s, int which)
 
         RECORD_LAYER_reset_read_sequence(&s->rlayer);
     } else {
-        s->statem.invalid_enc_write_ctx = 1;
+        s->statem.enc_write_state = ENC_WRITE_STATE_INVALID;
         if (s->enc_write_ctx != NULL) {
             EVP_CIPHER_CTX_reset(s->enc_write_ctx);
         } else {
@@ -602,12 +611,11 @@ int tls13_change_cipher_state(SSL *s, int which)
         if (!tls13_hkdf_expand(s, ssl_handshake_md(s), insecret,
                                resumption_master_secret,
                                sizeof(resumption_master_secret) - 1,
-                               hashval, hashlen, s->session->master_key,
+                               hashval, hashlen, s->resumption_master_secret,
                                hashlen)) {
             /* SSLfatal() already called */
             goto err;
         }
-        s->session->master_key_length = hashlen;
     }
 
     if (!derive_secret_key_and_iv(s, which & SSL3_CC_WRITE, md, cipher,
@@ -649,7 +657,10 @@ int tls13_change_cipher_state(SSL *s, int which)
         goto err;
     }
 
-    s->statem.invalid_enc_write_ctx = 0;
+    if (!s->server && label == client_early_traffic)
+        s->statem.enc_write_state = ENC_WRITE_STATE_WRITE_PLAIN_ALERTS;
+    else
+        s->statem.enc_write_state = ENC_WRITE_STATE_VALID;
     ret = 1;
  err:
     OPENSSL_cleanse(secret, sizeof(secret));
@@ -672,7 +683,7 @@ int tls13_update_key(SSL *s, int sending)
         insecret = s->client_app_traffic_secret;
 
     if (sending) {
-        s->statem.invalid_enc_write_ctx = 1;
+        s->statem.enc_write_state = ENC_WRITE_STATE_INVALID;
         iv = s->write_iv;
         ciph_ctx = s->enc_write_ctx;
         RECORD_LAYER_reset_write_sequence(&s->rlayer);
@@ -693,7 +704,7 @@ int tls13_update_key(SSL *s, int sending)
 
     memcpy(insecret, secret, hashlen);
 
-    s->statem.invalid_enc_write_ctx = 0;
+    s->statem.enc_write_state = ENC_WRITE_STATE_VALID;
     ret = 1;
  err:
     OPENSSL_cleanse(secret, sizeof(secret));
@@ -702,7 +713,8 @@ int tls13_update_key(SSL *s, int sending)
 
 int tls13_alert_code(int code)
 {
-    if (code == SSL_AD_MISSING_EXTENSION)
+    /* There are 2 additional alerts in TLSv1.3 compared to TLSv1.2 */
+    if (code == SSL_AD_MISSING_EXTENSION || code == SSL_AD_CERTIFICATE_REQUIRED)
         return code;
 
     return tls1_alert_code(code);