SSL AEAD support.

This change allows AEADs to be used in ssl/ to implement SSL/TLS
ciphersuites.

ssl/s3_enc.c

@@ -371,7 +371,13 @@ int ssl3_setup_key_block(SSL *s)
 	if (s->s3->tmp.key_block_length != 0)
 		return(1);
 
-	if (!ssl_cipher_get_evp(s->session,&c,&hash,NULL,NULL,&comp))
+	if (!ssl_cipher_get_comp(s->session, &comp))
+		{
+		OPENSSL_PUT_ERROR(SSL, ssl3_setup_key_block, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
+		return(0);
+		}
+
+	if (!ssl_cipher_get_evp(s->session,&c,&hash,NULL,NULL))
 		{
 		OPENSSL_PUT_ERROR(SSL, ssl3_setup_key_block, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
 		return(0);

ssl/s3_pkt.c

@@ -765,7 +765,9 @@ static int do_ssl3_write(SSL *s, int type, const unsigned char *buf,
 		else
 			eivlen = 0;
 		}
-	else 
+	else if (s->aead_write_ctx != NULL)
+		eivlen = s->aead_write_ctx->variable_nonce_len;
+	else
 		eivlen = 0;
 
 	/* lets setup the record stuff. */

ssl/ssl.h

@@ -438,7 +438,9 @@ struct ssl_cipher_st
 	unsigned long algorithm_ssl;	/* (major) protocol version */
 
 	unsigned long algo_strength;	/* strength and export flags */
-	unsigned long algorithm2;	/* Extra flags */
+	unsigned long algorithm2;	/* Extra flags. See SSL2_CF_* in ssl2.h
+					   and algorithm2 section in
+					   ssl_locl.h */
 	int strength_bits;		/* Number of bits really used */
 	int alg_bits;			/* Number of bits for algorithm */
 	};
@@ -825,6 +827,9 @@ void SSL_set_msg_callback(SSL *ssl, void (*cb)(int write_p, int version, int con
 #define SSL_set_msg_callback_arg(ssl, arg) SSL_ctrl((ssl), SSL_CTRL_SET_MSG_CALLBACK_ARG, 0, (arg))
 
 
+struct ssl_aead_ctx_st;
+typedef struct ssl_aead_ctx_st SSL_AEAD_CTX;
+
 #if defined(OPENSSL_SYS_MSDOS) && !defined(OPENSSL_SYS_WIN32)
 #define SSL_MAX_CERT_LIST_DEFAULT 1024*30 /* 30k max cert list :-) */
 #else
@@ -1404,10 +1409,16 @@ struct ssl_st
 	/* These are the ones being used, the ones in SSL_SESSION are
 	 * the ones to be 'copied' into these ones */
 	int mac_flags; 
+	SSL_AEAD_CTX *aead_read_ctx;	/* AEAD context. If non-NULL, then
+					   |enc_read_ctx| and |read_hash| are
+					   ignored. */
 	EVP_CIPHER_CTX *enc_read_ctx;		/* cryptographic state */
 	EVP_MD_CTX *read_hash;		/* used for mac generation */
 	char *expand;
 
+	SSL_AEAD_CTX *aead_write_ctx;	/* AEAD context. If non-NULL, then
+					   |enc_write_ctx| and |write_hash| are
+					   ignored. */
 	EVP_CIPHER_CTX *enc_write_ctx;		/* cryptographic state */
 	EVP_MD_CTX *write_hash;		/* used for mac generation */
 	char *compress;	
@@ -2658,6 +2669,8 @@ void ERR_load_SSL_strings(void);
 #define SSL_F_ssl3_send_channel_id 276
 #define SSL_F_SSL_CTX_set_cipher_list_tls11 277
 #define SSL_F_tls1_change_cipher_state_cipher 278
+#define SSL_F_tls1_change_cipher_state_aead 279
+#define SSL_F_tls1_aead_ctx_init 280
 #define SSL_R_UNABLE_TO_FIND_ECDH_PARAMETERS 100
 #define SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC 101
 #define SSL_R_INVALID_NULL_CMD_NAME 102

ssl/ssl3.h

@@ -529,6 +529,7 @@ typedef struct ssl3_state_st
 		unsigned char *key_block;
 
 		const EVP_CIPHER *new_sym_enc;
+		const EVP_AEAD *new_aead;
 		const EVP_MD *new_hash;
 		int new_mac_pkey_type;
 		int new_mac_secret_size;

ssl/ssl_ciph.c

@@ -350,29 +350,62 @@ void ssl_load_ciphers(void)
 	ssl_mac_secret_size[SSL_MD_SHA384_IDX]= EVP_MD_size(EVP_sha384());
 	}
 
+/* ssl_cipher_get_comp sets |comp| to the correct SSL_COMP for the given
+ * session and returns 1. On error it returns 0. */
+int ssl_cipher_get_comp(const SSL_SESSION *s, SSL_COMP **comp)
+	{
+	size_t index;
+
+	SSL_COMP ctmp;
+
+	*comp=NULL;
+	ctmp.id=s->compress_meth;
+	if (ssl_comp_methods != NULL)
+		{
+		if (sk_SSL_COMP_find(ssl_comp_methods, &index, &ctmp))
+			*comp=sk_SSL_COMP_value(ssl_comp_methods,index);
+		else
+			*comp=NULL;
+		}
+
+	return 1;
+	}
+
+/* ssl_cipher_get_evp_aead sets |*aead| to point to the correct EVP_AEAD object
+ * for |s->cipher|. It returns 1 on success and 0 on error. */
+int ssl_cipher_get_evp_aead(const SSL_SESSION *s, const EVP_AEAD **aead)
+	{
+	const SSL_CIPHER *c = s->cipher;
+
+	*aead = NULL;
+
+	if (c == NULL)
+		return 0;
+	if ((c->algorithm2 & SSL_CIPHER_ALGORITHM2_AEAD) == 0)
+		return 0;
+
+#ifndef OPENSSL_NO_AES
+	/* There is only one AEAD for now. */
+	*aead = EVP_aead_aes_128_gcm();
+	return 1;
+#endif
+
+	return 0;
+	}
+
 int ssl_cipher_get_evp(const SSL_SESSION *s, const EVP_CIPHER **enc,
-	     const EVP_MD **md, int *mac_pkey_type, int *mac_secret_size,SSL_COMP **comp)
+	     const EVP_MD **md, int *mac_pkey_type, int *mac_secret_size)
 	{
-	size_t compression_index;
 	int i;
 	const SSL_CIPHER *c;
 
 	c=s->cipher;
 	if (c == NULL) return(0);
-	if (comp != NULL)
-		{
-		SSL_COMP ctmp;
 
-		*comp=NULL;
-		ctmp.id=s->compress_meth;
-		if (ssl_comp_methods != NULL)
-			{
-			if (sk_SSL_COMP_find(ssl_comp_methods, &compression_index, &ctmp))
-				*comp=sk_SSL_COMP_value(ssl_comp_methods, compression_index);
-			else
-				*comp=NULL;
-			}
-		}
+	/* This function doesn't deal with EVP_AEAD. See
+	 * |ssl_cipher_get_aead_evp|. */
+	if (c->algorithm2 & SSL_CIPHER_ALGORITHM2_AEAD)
+		return(0);
 
 	if ((enc == NULL) || (md == NULL)) return(0);
 

ssl/ssl_error.c

@@ -188,8 +188,10 @@ const ERR_STRING_DATA SSL_error_string_data[] = {
   {ERR_PACK(ERR_LIB_SSL, SSL_F_ssl_verify_cert_chain, 0), "ssl_verify_cert_chain"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls12_check_peer_sigalg, 0), "tls12_check_peer_sigalg"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_PRF, 0), "tls1_PRF"},
+  {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_aead_ctx_init, 0), "tls1_aead_ctx_init"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_cert_verify_mac, 0), "tls1_cert_verify_mac"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_change_cipher_state, 0), "tls1_change_cipher_state"},
+  {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_change_cipher_state_aead, 0), "tls1_change_cipher_state_aead"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_change_cipher_state_cipher, 0), "tls1_change_cipher_state_cipher"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_export_keying_material, 0), "tls1_export_keying_material"},
   {ERR_PACK(ERR_LIB_SSL, SSL_F_tls1_get_server_supplemental_data, 0), "tls1_get_server_supplemental_data"},

ssl/ssl_lib.c

@@ -2914,6 +2914,18 @@ void ssl_clear_cipher_ctx(SSL *s)
 		OPENSSL_free(s->enc_write_ctx);
 		s->enc_write_ctx=NULL;
 		}
+	if (s->aead_read_ctx != NULL)
+		{
+		EVP_AEAD_CTX_cleanup(&s->aead_read_ctx->ctx);
+		OPENSSL_free(s->aead_read_ctx);
+		s->aead_read_ctx = NULL;
+		}
+	if (s->aead_write_ctx != NULL)
+		{
+		EVP_AEAD_CTX_cleanup(&s->aead_write_ctx->ctx);
+		OPENSSL_free(s->aead_write_ctx);
+		s->aead_write_ctx = NULL;
+		}
 	}
 
 X509 *SSL_get_certificate(const SSL *s)

ssl/ssl_locl.h

@@ -149,6 +149,7 @@
 #include <string.h>
 #include <time.h>
 
+#include <openssl/aead.h>
 #include <openssl/bio.h>
 #include <openssl/buf.h>
 #include <openssl/dsa.h>
@@ -367,6 +368,14 @@
 
 #define TLSEXT_CHANNEL_ID_SIZE 128
 
+/* SSL_CIPHER_ALGORITHM2_AEAD is a flag in SSL_CIPHER.algorithm2 which
+ * indicates that the cipher is implemented via an EVP_AEAD. */
+#define SSL_CIPHER_ALGORITHM2_AEAD (1<<23)
+
+/* SSL_CIPHER_AEAD_FIXED_NONCE_LEN returns the number of bytes of fixed nonce
+ * for an SSL_CIPHER* with the SSL_CIPHER_ALGORITHM2_AEAD flag. */
+#define SSL_CIPHER_AEAD_FIXED_NONCE_LEN(ssl_cipher) \
+	(((ssl_cipher->algorithm2 >> 24) & 0xf)*2)
 
 /*
  * Export and cipher strength information. For each cipher we have to decide
@@ -729,6 +738,17 @@ typedef struct ssl3_enc_method
  */
 #define SSL_ENC_FLAG_TLS1_2_CIPHERS	0x10
 
+/* ssl_aead_ctx_st contains information about an AEAD that is being used to
+ * encrypt an SSL connection. */
+struct ssl_aead_ctx_st
+	{
+	EVP_AEAD_CTX ctx;
+	/* fixed_nonce contains any bytes of the nonce that are fixed for all
+	 * records. */
+	unsigned char fixed_nonce[8];
+	unsigned char fixed_nonce_len, variable_nonce_len, tag_len;
+	};
+
 #ifndef OPENSSL_NO_COMP
 /* Used for holding the relevant compression methods loaded into SSL_CTX */
 typedef struct ssl3_comp_st
@@ -978,8 +998,11 @@ STACK_OF(SSL_CIPHER) *ssl_create_cipher_list(const SSL_METHOD *meth,
 					     STACK_OF(SSL_CIPHER) **sorted,
 					     const char *rule_str, CERT *c);
 void ssl_update_cache(SSL *s, int mode);
+int ssl_cipher_get_comp(const SSL_SESSION *s, SSL_COMP **comp);
+int ssl_cipher_get_evp_aead(const SSL_SESSION *s, const EVP_AEAD **aead);
 int ssl_cipher_get_evp(const SSL_SESSION *s,const EVP_CIPHER **enc,
-		       const EVP_MD **md,int *mac_pkey_type,int *mac_secret_size, SSL_COMP **comp);
+		       const EVP_MD **md,int *mac_pkey_type,int *mac_secret_size);
+int ssl_get_handshake_digest(int i,long *mask,const EVP_MD **md);			   
 int ssl_get_handshake_digest(int i,long *mask,const EVP_MD **md);
 int ssl_cipher_get_cert_index(const SSL_CIPHER *c);
 const SSL_CIPHER *ssl_get_cipher_by_char(SSL *ssl, const unsigned char *ptr);

ssl/ssl_txt.c

@@ -133,7 +133,10 @@ int SSL_SESSION_print(BIO *bp, const SSL_SESSION *x)
 
 	if (x->cipher == NULL)
 		{
-		if (((x->cipher_id) & 0xff000000) == 0x02000000)
+		SSL_COMP *comp = NULL;
+
+		ssl_cipher_get_comp(x, &comp);
+		if (comp == NULL)
 			{
 			if (BIO_printf(bp,"    Cipher    : %06lX\n",x->cipher_id&0xffffff) <= 0)
 				goto err;

ssl/t1_enc.c

@@ -311,6 +311,66 @@ static int tls1_generate_key_block(SSL *s, unsigned char *km,
 	return ret;
 	}
 
+/* tls1_aead_ctx_init allocates |*aead_ctx|, if needed and returns 1. It
+ * returns 0 on malloc error. */
+static int tls1_aead_ctx_init(SSL_AEAD_CTX **aead_ctx)
+	{
+	if (*aead_ctx != NULL)
+		EVP_AEAD_CTX_cleanup(&(*aead_ctx)->ctx);
+	else
+		{
+		*aead_ctx = (SSL_AEAD_CTX*) OPENSSL_malloc(sizeof(SSL_AEAD_CTX));
+		if (*aead_ctx == NULL)
+			{
+			OPENSSL_PUT_ERROR(SSL, tls1_aead_ctx_init, ERR_R_MALLOC_FAILURE);
+			return 0;
+			}
+		}
+
+	return 1;
+	}
+
+static int tls1_change_cipher_state_aead(SSL *s, char is_read,
+	const unsigned char *key, unsigned key_len,
+	const unsigned char *iv, unsigned iv_len)
+	{
+	const EVP_AEAD *aead = s->s3->tmp.new_aead;
+	SSL_AEAD_CTX *aead_ctx;
+
+	if (is_read)
+		{
+		if (!tls1_aead_ctx_init(&s->aead_read_ctx))
+			return 0;
+		aead_ctx = s->aead_read_ctx;
+		}
+	else
+		{
+		if (!tls1_aead_ctx_init(&s->aead_write_ctx))
+			return 0;
+		aead_ctx = s->aead_write_ctx;
+		}
+
+	if (!EVP_AEAD_CTX_init(&aead_ctx->ctx, aead, key, key_len,
+			       EVP_AEAD_DEFAULT_TAG_LENGTH, NULL /* engine */))
+		return 0;
+	if (iv_len > sizeof(aead_ctx->fixed_nonce))
+		{
+		OPENSSL_PUT_ERROR(SSL, tls1_change_cipher_state_aead, ERR_R_INTERNAL_ERROR);
+		return 0;
+		}
+	memcpy(aead_ctx->fixed_nonce, iv, iv_len);
+	aead_ctx->fixed_nonce_len = iv_len;
+	aead_ctx->variable_nonce_len = 8;  /* always the case, currently. */
+	if (aead_ctx->variable_nonce_len + aead_ctx->fixed_nonce_len != EVP_AEAD_nonce_length(aead))
+		{
+		OPENSSL_PUT_ERROR(SSL, tls1_change_cipher_state_aead, ERR_R_INTERNAL_ERROR);
+		return 0;
+		}
+	aead_ctx->tag_len = EVP_AEAD_max_overhead(aead);
+
+	return 1;
+	}
+
 /* tls1_change_cipher_state_cipher performs the work needed to switch cipher
  * states when using EVP_CIPHER. The argument |is_read| is true iff this
  * function is being called due to reading, as opposed to writing, a
@@ -500,6 +560,7 @@ int tls1_change_cipher_state(SSL *s, int which)
 	const unsigned char *client_write_key, *server_write_key, *key;
 	const unsigned char *client_write_iv, *server_write_iv, *iv;
 	const EVP_CIPHER *cipher = s->s3->tmp.new_sym_enc;
+	const EVP_AEAD *aead = s->s3->tmp.new_aead;
 	unsigned key_len, iv_len, mac_secret_len;
 	const unsigned char *key_data;
 	const char is_export = SSL_C_IS_EXPORT(s->s3->tmp.new_cipher) != 0;
@@ -513,14 +574,22 @@ int tls1_change_cipher_state(SSL *s, int which)
 
 	mac_secret_len = s->s3->tmp.new_mac_secret_size;
 
-	key_len = EVP_CIPHER_key_length(cipher);
-	if (is_export && key_len > SSL_C_EXPORT_KEYLENGTH(s->s3->tmp.new_cipher))
-		key_len = SSL_C_EXPORT_KEYLENGTH(s->s3->tmp.new_cipher);
-
-	if (EVP_CIPHER_mode(cipher) == EVP_CIPH_GCM_MODE)
-		iv_len = EVP_GCM_TLS_FIXED_IV_LEN;
+	if (aead != NULL)
+		{
+		key_len = EVP_AEAD_key_length(aead);
+		iv_len = SSL_CIPHER_AEAD_FIXED_NONCE_LEN(s->s3->tmp.new_cipher);
+		}
 	else
-		iv_len = EVP_CIPHER_iv_length(cipher);
+		{
+		key_len = EVP_CIPHER_key_length(cipher);
+		if (is_export && key_len > SSL_C_EXPORT_KEYLENGTH(s->s3->tmp.new_cipher))
+			key_len = SSL_C_EXPORT_KEYLENGTH(s->s3->tmp.new_cipher);
+
+		if (EVP_CIPHER_mode(cipher) == EVP_CIPH_GCM_MODE)
+			iv_len = EVP_GCM_TLS_FIXED_IV_LEN;
+		else
+			iv_len = EVP_CIPHER_iv_length(cipher);
+		}
 
 	key_data = s->s3->tmp.key_block;
 	client_write_mac_secret = key_data; key_data += mac_secret_len;
@@ -549,12 +618,20 @@ int tls1_change_cipher_state(SSL *s, int which)
 		return 0;
 		}
 
-	if (!tls1_change_cipher_state_cipher(s, is_read, use_client_keys,
-					     mac_secret, mac_secret_len,
-					     key, key_len,
-					     iv, iv_len)) {
-		return 0;
-	}
+	if (aead != NULL)
+		{
+		if (!tls1_change_cipher_state_aead(s, is_read,
+						   key, key_len, iv, iv_len))
+			return 0;
+		}
+	else
+		{
+		if (!tls1_change_cipher_state_cipher(s, is_read, use_client_keys,
+						     mac_secret, mac_secret_len,
+						     key, key_len,
+						     iv, iv_len))
+			return 0;
+		}
 
 	return 1;
 	}
@@ -562,13 +639,14 @@ int tls1_change_cipher_state(SSL *s, int which)
 int tls1_setup_key_block(SSL *s)
 	{
 	unsigned char *p1,*p2=NULL;
-	const EVP_CIPHER *c;
-	const EVP_MD *hash;
+	const EVP_CIPHER *c = NULL;
+	const EVP_MD *hash = NULL;
+	const EVP_AEAD *aead = NULL;
 	int num;
 	SSL_COMP *comp;
 	int mac_type= NID_undef,mac_secret_size=0;
 	int ret=0;
-	int iv_len;
+	unsigned key_len, iv_len;
 
 #ifdef KSSL_DEBUG
 	printf ("tls1_setup_key_block()\n");
@@ -577,22 +655,36 @@ int tls1_setup_key_block(SSL *s)
 	if (s->s3->tmp.key_block_length != 0)
 		return(1);
 
-	if (!ssl_cipher_get_evp(s->session,&c,&hash,&mac_type,&mac_secret_size,&comp))
+	if (!ssl_cipher_get_comp(s->session, &comp))
+		goto cipher_unavailable_err;
+
+	if (s->session->cipher &&
+	    (s->session->cipher->algorithm2 & SSL_CIPHER_ALGORITHM2_AEAD))
 		{
-		OPENSSL_PUT_ERROR(SSL, tls1_setup_key_block, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
-		return(0);
+		if (!ssl_cipher_get_evp_aead(s->session, &aead))
+			goto cipher_unavailable_err;
+		key_len = EVP_AEAD_key_length(aead);
+		iv_len = SSL_CIPHER_AEAD_FIXED_NONCE_LEN(s->session->cipher);
 		}
-
-	if (EVP_CIPHER_mode(c) == EVP_CIPH_GCM_MODE)
-		iv_len = EVP_GCM_TLS_FIXED_IV_LEN;
 	else
-		iv_len = EVP_CIPHER_iv_length(c);
+		{
+		if (!ssl_cipher_get_evp(s->session,&c,&hash,&mac_type,&mac_secret_size))
+			goto cipher_unavailable_err;
+		key_len = EVP_CIPHER_key_length(c);
 
+		if (EVP_CIPHER_mode(c) == EVP_CIPH_GCM_MODE)
+			iv_len = EVP_GCM_TLS_FIXED_IV_LEN;
+		else
+			iv_len = EVP_CIPHER_iv_length(c);
+		}
+
+	s->s3->tmp.new_aead=aead;
 	s->s3->tmp.new_sym_enc=c;
 	s->s3->tmp.new_hash=hash;
 	s->s3->tmp.new_mac_pkey_type = mac_type;
 	s->s3->tmp.new_mac_secret_size = mac_secret_size;
-	num=EVP_CIPHER_key_length(c)+mac_secret_size+iv_len;
+
+	num=key_len+mac_secret_size+iv_len;
 	num*=2;
 
 	ssl3_cleanup_key_block(s);
@@ -655,6 +747,10 @@ err:
 		OPENSSL_free(p2);
 		}
 	return(ret);
+
+cipher_unavailable_err:
+	OPENSSL_PUT_ERROR(SSL, tls1_setup_key_block, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
+	return 0;
 	}
 
 /* tls1_enc encrypts/decrypts the record in |s->wrec| / |s->rrec|, respectively.
@@ -673,6 +769,132 @@ int tls1_enc(SSL *s, int send)
 	unsigned long l;
 	int bs,i,j,k,pad=0,ret,mac_size=0;
 	const EVP_CIPHER *enc;
+	const SSL_AEAD_CTX *aead;
+
+	if (send)
+		rec = &s->s3->wrec;
+	else
+		rec = &s->s3->rrec;
+
+	if (send)
+		aead = s->aead_write_ctx;
+	else
+		aead = s->aead_read_ctx;
+
+	if (aead)
+		{
+		unsigned char ad[13], *seq, *in, *out, nonce[16];
+		unsigned nonce_used;
+		size_t n;
+
+		seq = send ? s->s3->write_sequence : s->s3->read_sequence;
+
+		if (s->version == DTLS1_VERSION || s->version == DTLS1_BAD_VER)
+			{
+			unsigned char dtlsseq[9], *p = dtlsseq;
+
+			s2n(send ? s->d1->w_epoch : s->d1->r_epoch, p);
+			memcpy(p, &seq[2], 6);
+			memcpy(ad, dtlsseq, 8);
+			}
+		else
+			{
+			memcpy(ad, seq, 8);
+			for (i=7; i>=0; i--)	/* increment */
+				{
+				++seq[i];
+				if (seq[i] != 0)
+					break;
+				}
+			}
+
+		ad[8]  = rec->type;
+		ad[9]  = (unsigned char)(s->version>>8);
+		ad[10] = (unsigned char)(s->version);
+
+		if (aead->fixed_nonce_len + aead->variable_nonce_len > sizeof(nonce) ||
+		    aead->variable_nonce_len > 8)
+			return -1;  /* internal error - should never happen. */
+
+		memcpy(nonce, aead->fixed_nonce, aead->fixed_nonce_len);
+		nonce_used = aead->fixed_nonce_len;
+
+		if (send)
+			{
+			size_t len = rec->length;
+			in = rec->input;
+			out = rec->data;
+
+			/* When sending we use the sequence number as the
+			 * variable part of the nonce. */
+			if (aead->variable_nonce_len > 8)
+				return -1;
+			memcpy(nonce + nonce_used, ad, aead->variable_nonce_len);
+			nonce_used += aead->variable_nonce_len;
+
+			/* in do_ssl3_write, rec->input is moved forward by
+			 * variable_nonce_len in order to leave space for the
+			 * variable nonce. Thus we can copy the sequence number
+			 * bytes into place without overwriting any of the
+			 * plaintext. */
+			memcpy(out, ad, aead->variable_nonce_len);
+			len -= aead->variable_nonce_len;
+
+			ad[11] = len >> 8;
+			ad[12] = len & 0xff;
+
+			if (!EVP_AEAD_CTX_seal(
+				&aead->ctx,
+				out + aead->variable_nonce_len, &n, len + aead->tag_len,
+				nonce, nonce_used,
+				in + aead->variable_nonce_len, len,
+				ad, sizeof(ad)))
+				{
+				return -1;
+				}
+			n += aead->variable_nonce_len;
+			}
+		else
+			{
+			/* receive */
+			size_t len = rec->length;
+
+			if (rec->data != rec->input)
+				return -1;  /* internal error - should never happen. */
+			out = in = rec->input;
+
+			if (len < aead->variable_nonce_len)
+				return 0;
+			memcpy(nonce + nonce_used, in, aead->variable_nonce_len);
+			nonce_used += aead->variable_nonce_len;
+
+			in += aead->variable_nonce_len;
+			len -= aead->variable_nonce_len;
+			out += aead->variable_nonce_len;
+
+			if (len < aead->tag_len)
+				return 0;
+			len -= aead->tag_len;
+
+			ad[11] = len >> 8;
+			ad[12] = len & 0xff;
+
+			if (!EVP_AEAD_CTX_open(
+				&aead->ctx,
+				out, &n, len,
+				nonce, nonce_used,
+				in, len + aead->tag_len,
+				ad, sizeof(ad)))
+				{
+				return -1;
+				}
+
+			rec->data = rec->input = out;
+			}
+
+		rec->length = n;
+		return 1;
+		}
 
 	if (send)
 		{