From: Michael Brown <mcb30@ipxe.org>
Date: Fri, 19 Jun 2026 12:26:00 +0000 (+0100)
Subject: [crypto] Use private data field for cipher algorithms
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;p=thirdparty%2Fipxe.git

[crypto] Use private data field for cipher algorithms

Following the example of commit 25072c1 ("[crypto] Use private data
field for key exchange algorithms"), extend the definition of a cipher
algorithm to include an opaque private data field, and use this to
eliminate the wrapper functions generated for the various block cipher
modes of operation by ECB_CIPHER(), CBC_CIPHER(), and GCM_CIPHER().

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---

diff --git a/src/crypto/aes.c b/src/crypto/aes.c
index fe6ccb222..c98361474 100644
--- a/src/crypto/aes.c
+++ b/src/crypto/aes.c
@@ -391,12 +391,14 @@ static void aes_final ( const struct aes_table *table, size_t stride,
 /**
  * Encrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to encrypt
  * @v dst		Buffer for encrypted data
  * @v len		Length of data
  */
-static void aes_encrypt ( void *ctx, const void *src, void *dst, size_t len ) {
+static void aes_encrypt ( struct cipher_algorithm *cipher __unused, void *ctx,
+			  const void *src, void *dst, size_t len ) {
 	struct aes_context *aes = ctx;
 	union aes_matrix buffer[2];
 	union aes_matrix *in = &buffer[0];
@@ -427,12 +429,14 @@ static void aes_encrypt ( void *ctx, const void *src, void *dst, size_t len ) {
 /**
  * Decrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to decrypt
  * @v dst		Buffer for decrypted data
  * @v len		Length of data
  */
-static void aes_decrypt ( void *ctx, const void *src, void *dst, size_t len ) {
+static void aes_decrypt ( struct cipher_algorithm *cipher __unused, void *ctx,
+			  const void *src, void *dst, size_t len ) {
 	struct aes_context *aes = ctx;
 	union aes_matrix buffer[2];
 	union aes_matrix *in = &buffer[0];
@@ -674,12 +678,14 @@ aes_key_rcon ( uint32_t column, unsigned int rcon ) {
 /**
  * Set key
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v key		Key
  * @v keylen		Key length
  * @ret rc		Return status code
  */
-static int aes_setkey ( void *ctx, const void *key, size_t keylen ) {
+static int aes_setkey ( struct cipher_algorithm *cipher __unused, void *ctx,
+			const void *key, size_t keylen ) {
 	struct aes_context *aes = ctx;
 	union aes_matrix *enc;
 	union aes_matrix *dec;
diff --git a/src/crypto/arc4.c b/src/crypto/arc4.c
index 3b6adec19..2866688eb 100644
--- a/src/crypto/arc4.c
+++ b/src/crypto/arc4.c
@@ -30,6 +30,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 /**
  * Set ARC4 key
  *
+ * @v cipher	Cipher algorithm
  * @v ctxv	ARC4 encryption context
  * @v keyv	Key to set
  * @v keylen	Length of key
@@ -39,7 +40,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
  * there is no standard length for an initialisation vector in the
  * cipher.
  */
-static int arc4_setkey ( void *ctxv, const void *keyv, size_t keylen )
+static int arc4_setkey ( struct cipher_algorithm *cipher __unused, void *ctxv,
+			 const void *keyv, size_t keylen )
 {
 	struct arc4_ctx *ctx = ctxv;
 	const u8 *key = keyv;
@@ -62,6 +64,7 @@ static int arc4_setkey ( void *ctxv, const void *keyv, size_t keylen )
 /**
  * Perform ARC4 encryption or decryption
  *
+ * @v cipher	Cipher algorithm
  * @v ctxv	ARC4 encryption context
  * @v srcv	Data to encrypt or decrypt
  * @v dstv	Location to store encrypted or decrypted data
@@ -75,8 +78,8 @@ static int arc4_setkey ( void *ctxv, const void *keyv, size_t keylen )
  * If you pass a @c NULL source or destination pointer, @a len
  * keystream bytes will be consumed without encrypting any data.
  */
-static void arc4_xor ( void *ctxv, const void *srcv, void *dstv,
-		       size_t len )
+static void arc4_xor ( struct cipher_algorithm *cipher __unused, void *ctxv,
+		       const void *srcv, void *dstv, size_t len )
 {
 	struct arc4_ctx *ctx = ctxv;
 	const u8 *src = srcv;
@@ -109,10 +112,12 @@ static void arc4_xor ( void *ctxv, const void *srcv, void *dstv,
 void arc4_skip ( const void *key, size_t keylen, size_t skip,
 		 const void *src, void *dst, size_t msglen )
 {
+	struct cipher_algorithm *cipher = &arc4_algorithm;
 	struct arc4_ctx ctx;
-	arc4_setkey ( &ctx, key, keylen );
-	arc4_xor ( &ctx, NULL, NULL, skip );
-	arc4_xor ( &ctx, src, dst, msglen );
+
+	arc4_setkey ( cipher, &ctx, key, keylen );
+	arc4_xor ( cipher, &ctx, NULL, NULL, skip );
+	arc4_xor ( cipher, &ctx, src, dst, msglen );
 }
 
 struct cipher_algorithm arc4_algorithm = {
diff --git a/src/crypto/cbc.c b/src/crypto/cbc.c
index ddba7abd9..ff45dd9e8 100644
--- a/src/crypto/cbc.c
+++ b/src/crypto/cbc.c
@@ -35,6 +35,43 @@ FILE_SECBOOT ( PERMITTED );
  *
  */
 
+/**
+ * Set key
+ *
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
+ * @v key		Key
+ * @v keylen		Key length
+ * @ret rc		Return status code
+ */
+int cbc_setkey ( struct cipher_algorithm *cipher, void *ctx,
+		 const void *key, size_t keylen ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+	size_t blocksize = cipher->blocksize;
+	size_t ctxsize = cipher->ctxsize;
+	cbc_context_t ( blocksize, ctxsize ) *context = ctx;
+
+	return cipher_setkey ( raw_cipher, context->raw, key, keylen );
+}
+
+/**
+ * Set initialisation vector
+ *
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
+ * @v iv		Initialisation vector
+ * @v ivlen		Initialisation vector length
+ */
+void cbc_setiv ( struct cipher_algorithm *cipher, void *ctx,
+		 const void *iv, size_t ivlen ) {
+	size_t blocksize = cipher->blocksize;
+	size_t ctxsize = cipher->ctxsize;
+	cbc_context_t ( blocksize, ctxsize ) *context = ctx;
+
+	assert ( ivlen == sizeof ( context->cbc ) );
+	memcpy ( context->cbc, iv, sizeof ( context->cbc ) );
+}
+
 /**
  * XOR data blocks
  *
@@ -57,23 +94,26 @@ static void cbc_xor ( const void *src, void *dst, size_t len ) {
 /**
  * Encrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to encrypt
  * @v dst		Buffer for encrypted data
  * @v len		Length of data
- * @v raw_cipher	Underlying cipher algorithm
- * @v cbc_ctx		CBC context
  */
-void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
-		   struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
-	size_t blocksize = raw_cipher->blocksize;
+void cbc_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+		   const void *src, void *dst, size_t len ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+	size_t blocksize = cipher->blocksize;
+	size_t ctxsize = cipher->ctxsize;
+	cbc_context_t ( blocksize, ctxsize ) *context = ctx;
 
 	assert ( ( len % blocksize ) == 0 );
 
 	while ( len ) {
-		cbc_xor ( src, cbc_ctx, blocksize );
-		cipher_encrypt ( raw_cipher, ctx, cbc_ctx, dst, blocksize );
-		memcpy ( cbc_ctx, dst, blocksize );
+		cbc_xor ( src, context->cbc, blocksize );
+		cipher_encrypt ( raw_cipher, context->raw, context->cbc, dst,
+				 blocksize );
+		memcpy ( context->cbc, dst, blocksize );
 		dst += blocksize;
 		src += blocksize;
 		len -= blocksize;
@@ -83,25 +123,28 @@ void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
 /**
  * Decrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to decrypt
  * @v dst		Buffer for decrypted data
  * @v len		Length of data
- * @v raw_cipher	Underlying cipher algorithm
- * @v cbc_ctx		CBC context
  */
-void cbc_decrypt ( void *ctx, const void *src, void *dst, size_t len,
-		   struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
-	size_t blocksize = raw_cipher->blocksize;
+void cbc_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+		   const void *src, void *dst, size_t len ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+	size_t blocksize = cipher->blocksize;
+	size_t ctxsize = cipher->ctxsize;
+	cbc_context_t ( blocksize, ctxsize ) *context = ctx;
 	uint8_t next_cbc_ctx[blocksize];
 
 	assert ( ( len % blocksize ) == 0 );
 
 	while ( len ) {
 		memcpy ( next_cbc_ctx, src, blocksize );
-		cipher_decrypt ( raw_cipher, ctx, src, dst, blocksize );
-		cbc_xor ( cbc_ctx, dst, blocksize );
-		memcpy ( cbc_ctx, next_cbc_ctx, blocksize );
+		cipher_decrypt ( raw_cipher, context->raw, src, dst,
+				 blocksize );
+		cbc_xor ( context->cbc, dst, blocksize );
+		memcpy ( context->cbc, next_cbc_ctx, blocksize );
 		dst += blocksize;
 		src += blocksize;
 		len -= blocksize;
diff --git a/src/crypto/crypto_null.c b/src/crypto/crypto_null.c
index 93580bb88..5d0531f11 100644
--- a/src/crypto/crypto_null.c
+++ b/src/crypto/crypto_null.c
@@ -60,28 +60,33 @@ struct digest_algorithm digest_null = {
 	.final = digest_null_final,
 };
 
-int cipher_null_setkey ( void *ctx __unused, const void *key __unused,
+int cipher_null_setkey ( struct cipher_algorithm *cipher __unused,
+			 void *ctx __unused, const void *key __unused,
 			 size_t keylen __unused ) {
 	/* Do nothing */
 	return 0;
 }
 
-void cipher_null_setiv ( void *ctx __unused, const void *iv __unused,
+void cipher_null_setiv ( struct cipher_algorithm *cipher __unused,
+			 void *ctx __unused, const void *iv __unused,
 			 size_t ivlen __unused ) {
 	/* Do nothing */
 }
 
-void cipher_null_encrypt ( void *ctx __unused, const void *src, void *dst,
+void cipher_null_encrypt ( struct cipher_algorithm *cipher __unused,
+			   void *ctx __unused, const void *src, void *dst,
 			   size_t len ) {
 	memcpy ( dst, src, len );
 }
 
-void cipher_null_decrypt ( void *ctx __unused, const void *src, void *dst,
+void cipher_null_decrypt ( struct cipher_algorithm *cipher __unused,
+			   void *ctx __unused, const void *src, void *dst,
 			   size_t len ) {
 	memcpy ( dst, src, len );
 }
 
-void cipher_null_auth ( void *ctx __unused, void *auth __unused ) {
+void cipher_null_auth ( struct cipher_algorithm *cipher __unused,
+			void *ctx __unused, void *auth __unused ) {
 	/* Do nothing */
 }
 
diff --git a/src/crypto/des.c b/src/crypto/des.c
index a7fad9829..938643e1b 100644
--- a/src/crypto/des.c
+++ b/src/crypto/des.c
@@ -580,12 +580,14 @@ static uint32_t des_rol28 ( uint32_t dword ) {
 /**
  * Set key
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v key		Key
  * @v keylen		Key length
  * @ret rc		Return status code
  */
-static int des_setkey ( void *ctx, const void *key, size_t keylen ) {
+static int des_setkey ( struct cipher_algorithm *cipher __unused, void *ctx,
+			const void *key, size_t keylen ) {
 	struct des_context *des = ctx;
 	union des_round_key *rkey = des->rkey;
 	union des_block reg;
@@ -640,12 +642,14 @@ static int des_setkey ( void *ctx, const void *key, size_t keylen ) {
 /**
  * Encrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to encrypt
  * @v dst		Buffer for encrypted data
  * @v len		Length of data
  */
-static void des_encrypt ( void *ctx, const void *src, void *dst, size_t len ) {
+static void des_encrypt ( struct cipher_algorithm *cipher __unused, void *ctx,
+			  const void *src, void *dst, size_t len ) {
 	struct des_context *des = ctx;
 
 	/* Sanity check */
@@ -658,12 +662,14 @@ static void des_encrypt ( void *ctx, const void *src, void *dst, size_t len ) {
 /**
  * Decrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to decrypt
  * @v dst		Buffer for decrypted data
  * @v len		Length of data
  */
-static void des_decrypt ( void *ctx, const void *src, void *dst, size_t len ) {
+static void des_decrypt ( struct cipher_algorithm *cipher __unused, void *ctx,
+			  const void *src, void *dst, size_t len ) {
 	struct des_context *des = ctx;
 
 	/* Sanity check */
diff --git a/src/crypto/ecb.c b/src/crypto/ecb.c
index 73eef09c2..754900cae 100644
--- a/src/crypto/ecb.c
+++ b/src/crypto/ecb.c
@@ -34,17 +34,34 @@ FILE_SECBOOT ( PERMITTED );
  *
  */
 
+/**
+ * Set key
+ *
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
+ * @v key		Key
+ * @v keylen		Key length
+ * @ret rc		Return status code
+ */
+int ecb_setkey ( struct cipher_algorithm *cipher, void *ctx,
+		 const void *key, size_t keylen ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+
+	return cipher_setkey ( raw_cipher, ctx, key, keylen );
+}
+
 /**
  * Encrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to encrypt
  * @v dst		Buffer for encrypted data
  * @v len		Length of data
- * @v raw_cipher	Underlying cipher algorithm
  */
-void ecb_encrypt ( void *ctx, const void *src, void *dst, size_t len,
-		   struct cipher_algorithm *raw_cipher ) {
+void ecb_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+		   const void *src, void *dst, size_t len ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
 	size_t blocksize = raw_cipher->blocksize;
 
 	assert ( ( len % blocksize ) == 0 );
@@ -60,14 +77,15 @@ void ecb_encrypt ( void *ctx, const void *src, void *dst, size_t len,
 /**
  * Decrypt data
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v src		Data to decrypt
  * @v dst		Buffer for decrypted data
  * @v len		Length of data
- * @v raw_cipher	Underlying cipher algorithm
  */
-void ecb_decrypt ( void *ctx, const void *src, void *dst, size_t len,
-		   struct cipher_algorithm *raw_cipher ) {
+void ecb_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+		   const void *src, void *dst, size_t len ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
 	size_t blocksize = raw_cipher->blocksize;
 
 	assert ( ( len % blocksize ) == 0 );
diff --git a/src/crypto/gcm.c b/src/crypto/gcm.c
index b9c9d3a39..c0e32a320 100644
--- a/src/crypto/gcm.c
+++ b/src/crypto/gcm.c
@@ -309,30 +309,55 @@ static void gcm_multiply_key ( const union gcm_block *key,
 }
 
 /**
- * Encrypt/decrypt/authenticate data
+ * Construct hash
  *
  * @v context		Context
+ * @v hash		Hash to fill in
+ */
+static void gcm_hash ( struct gcm_context *context, union gcm_block *hash ) {
+
+	/* Construct big-endian lengths block */
+	hash->len.add = cpu_to_be64 ( context->len.len.add );
+	hash->len.data = cpu_to_be64 ( context->len.len.data );
+	DBGC2 ( context, "GCM %p len(A)||len(C):\n", context );
+	DBGC2_HDA ( context, 0, hash, sizeof ( *hash ) );
+
+	/* Update hash */
+	gcm_xor_block ( &context->hash, hash );
+	gcm_multiply_key ( &context->key, hash );
+	DBGC2 ( context, "GCM %p GHASH(H,A,C):\n", context );
+	DBGC2_HDA ( context, 0, hash, sizeof ( *hash ) );
+}
+
+/**
+ * Encrypt/decrypt/authenticate data
+ *
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
  * @v src		Input data
  * @v dst		Output data, or NULL to process additional data
  * @v len		Length of data
  * @v flags		Operation flags
  */
-static void gcm_process ( struct gcm_context *context, const void *src,
-			  void *dst, size_t len, unsigned int flags ) {
+static void gcm_process ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+	gcm_context_t ( cipher->ctxsize ) *context = ctx;
+	unsigned int flags = context->gcm.flags;
 	union gcm_block tmp;
 	uint64_t *total;
 	size_t frag_len;
 	unsigned int block;
 
 	/* Calculate block number (for debugging) */
-	block = ( ( ( context->len.len.add + 8 * sizeof ( tmp ) - 1 ) /
+	block = ( ( ( context->gcm.len.len.add + 8 * sizeof ( tmp ) - 1 ) /
 		    ( 8 * sizeof ( tmp ) ) ) +
-		  ( ( context->len.len.data + 8 * sizeof ( tmp ) - 1 ) /
+		  ( ( context->gcm.len.len.data + 8 * sizeof ( tmp ) - 1 ) /
 		    ( 8 * sizeof ( tmp ) ) ) + 1 );
 
 	/* Update total length (in bits) */
 	total = ( ( dst || ( flags & GCM_FL_IV ) ) ?
-		  &context->len.len.data : &context->len.len.add );
+		  &context->gcm.len.len.data : &context->gcm.len.len.add );
 	*total += ( len * 8 );
 
 	/* Process data */
@@ -344,20 +369,22 @@ static void gcm_process ( struct gcm_context *context, const void *src,
 			frag_len = sizeof ( tmp );
 
 		/* Update hash with input data */
-		gcm_xor ( src, &context->hash, &context->hash, frag_len );
+		gcm_xor ( src, &context->gcm.hash, &context->gcm.hash,
+			  frag_len );
 
 		/* Encrypt/decrypt block, if applicable */
 		if ( dst ) {
 
 			/* Increment counter */
-			gcm_count ( &context->ctr, 1 );
+			gcm_count ( &context->gcm.ctr, 1 );
 
 			/* Encrypt counter */
 			DBGC2 ( context, "GCM %p Y[%d]:\n", context, block );
-			DBGC2_HDA ( context, 0, &context->ctr,
-				    sizeof ( context->ctr ) );
-			cipher_encrypt ( context->raw_cipher, &context->raw_ctx,
-					 &context->ctr, &tmp, sizeof ( tmp ) );
+			DBGC2_HDA ( context, 0, &context->gcm.ctr,
+				    sizeof ( context->gcm.ctr ) );
+			cipher_encrypt ( raw_cipher, &context->raw,
+					 &context->gcm.ctr, &tmp,
+					 sizeof ( tmp ) );
 			DBGC2 ( context, "GCM %p E(K,Y[%d]):\n",
 				context, block );
 			DBGC2_HDA ( context, 0, &tmp, sizeof ( tmp ) );
@@ -367,100 +394,53 @@ static void gcm_process ( struct gcm_context *context, const void *src,
 			dst += frag_len;
 
 			/* Update hash with encrypted data, if applicable */
-			gcm_xor ( &tmp, &context->hash, &context->hash,
+			gcm_xor ( &tmp, &context->gcm.hash, &context->gcm.hash,
 				  ( frag_len & flags ) );
 		}
 
 		/* Update hash */
-		gcm_multiply_key ( &context->key, &context->hash );
+		gcm_multiply_key ( &context->gcm.key, &context->gcm.hash );
 		DBGC2 ( context, "GCM %p X[%d]:\n", context, block );
-		DBGC2_HDA ( context, 0, &context->hash,
-			    sizeof ( context->hash ) );
+		DBGC2_HDA ( context, 0, &context->gcm.hash,
+			    sizeof ( context->gcm.hash ) );
 	}
 }
 
-/**
- * Construct hash
- *
- * @v context		Context
- * @v hash		Hash to fill in
- */
-static void gcm_hash ( struct gcm_context *context, union gcm_block *hash ) {
-
-	/* Construct big-endian lengths block */
-	hash->len.add = cpu_to_be64 ( context->len.len.add );
-	hash->len.data = cpu_to_be64 ( context->len.len.data );
-	DBGC2 ( context, "GCM %p len(A)||len(C):\n", context );
-	DBGC2_HDA ( context, 0, hash, sizeof ( *hash ) );
-
-	/* Update hash */
-	gcm_xor_block ( &context->hash, hash );
-	gcm_multiply_key ( &context->key, hash );
-	DBGC2 ( context, "GCM %p GHASH(H,A,C):\n", context );
-	DBGC2_HDA ( context, 0, hash, sizeof ( *hash ) );
-}
-
-/**
- * Construct tag
- *
- * @v context		Context
- * @v tag		Tag
- */
-void gcm_tag ( struct gcm_context *context, union gcm_block *tag ) {
-	union gcm_block tmp;
-	uint32_t offset;
-
-	/* Construct hash */
-	gcm_hash ( context, tag );
-
-	/* Construct encrypted initial counter value */
-	memcpy ( &tmp, &context->ctr, sizeof ( tmp ) );
-	offset = ( ( -context->len.len.data ) / ( 8 * sizeof ( tmp ) ) );
-	gcm_count ( &tmp, offset );
-	cipher_encrypt ( context->raw_cipher, &context->raw_ctx, &tmp,
-			 &tmp, sizeof ( tmp ) );
-	DBGC2 ( context, "GCM %p E(K,Y[0]):\n", context );
-	DBGC2_HDA ( context, 0, &tmp, sizeof ( tmp ) );
-
-	/* Construct tag */
-	gcm_xor_block ( &tmp, tag );
-	DBGC2 ( context, "GCM %p T:\n", context );
-	DBGC2_HDA ( context, 0, tag, sizeof ( *tag ) );
-}
-
 /**
  * Set key
  *
- * @v context		Context
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
  * @v key		Key
  * @v keylen		Key length
- * @v raw_cipher	Underlying cipher
  * @ret rc		Return status code
  */
-int gcm_setkey ( struct gcm_context *context, const void *key, size_t keylen,
-		 struct cipher_algorithm *raw_cipher ) {
+int gcm_setkey ( struct cipher_algorithm *cipher, void *ctx,
+		 const void *key, size_t keylen ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+	gcm_context_t ( cipher->ctxsize ) *context = ctx;
 	int rc;
 
 	/* Initialise GCM context */
-	memset ( context, 0, sizeof ( *context ) );
-	context->raw_cipher = raw_cipher;
+	memset ( &context->gcm, 0, sizeof ( context->gcm ) );
 
 	/* Set underlying block cipher key */
-	if ( ( rc = cipher_setkey ( raw_cipher, context->raw_ctx, key,
+	if ( ( rc = cipher_setkey ( raw_cipher, context->raw, key,
 				    keylen ) ) != 0 )
 		return rc;
 
 	/* Construct GCM hash key */
-	cipher_encrypt ( raw_cipher, context->raw_ctx, &context->ctr,
-			 &context->key, sizeof ( context->key ) );
+	cipher_encrypt ( raw_cipher, context->raw, &context->gcm.ctr,
+			 &context->gcm.key, sizeof ( context->gcm.key ) );
 	DBGC2 ( context, "GCM %p H:\n", context );
-	DBGC2_HDA ( context, 0, &context->key, sizeof ( context->key ) );
+	DBGC2_HDA ( context, 0, &context->gcm.key,
+		    sizeof ( context->gcm.key ) );
 
 	/* Reset counter */
-	context->ctr.ctr.value = cpu_to_be32 ( 1 );
+	context->gcm.ctr.ctr.value = cpu_to_be32 ( 1 );
 
 	/* Construct cached tables */
-	gcm_cache ( &context->key );
+	gcm_cache ( &context->gcm.key );
 
 	return 0;
 }
@@ -468,75 +448,114 @@ int gcm_setkey ( struct gcm_context *context, const void *key, size_t keylen,
 /**
  * Set initialisation vector
  *
+ * @v cipher		Cipher algorithm
  * @v ctx		Context
  * @v iv		Initialisation vector
  * @v ivlen		Initialisation vector length
  */
-void gcm_setiv ( struct gcm_context *context, const void *iv, size_t ivlen ) {
+void gcm_setiv ( struct cipher_algorithm *cipher, void *ctx,
+		 const void *iv, size_t ivlen ) {
+	gcm_context_t ( cipher->ctxsize ) *context = ctx;
 
 	/* Reset non-key state */
-	memset ( context, 0, gcm_offset ( key ) );
+	memset ( &context->gcm, 0, gcm_offset ( key ) );
 	build_assert ( gcm_offset ( key ) > gcm_offset ( hash ) );
 	build_assert ( gcm_offset ( key ) > gcm_offset ( len ) );
 	build_assert ( gcm_offset ( key ) > gcm_offset ( ctr ) );
-	build_assert ( gcm_offset ( key ) < gcm_offset ( raw_cipher ) );
-	build_assert ( gcm_offset ( key ) < gcm_offset ( raw_ctx ) );
 
 	/* Reset counter */
-	context->ctr.ctr.value = cpu_to_be32 ( 1 );
+	context->gcm.ctr.ctr.value = cpu_to_be32 ( 1 );
 
 	/* Process initialisation vector */
-	if ( ivlen == sizeof ( context->ctr.ctr.iv ) ) {
+	if ( ivlen == sizeof ( context->gcm.ctr.ctr.iv ) ) {
 
 		/* Initialisation vector is exactly 96 bits, use it as-is */
-		memcpy ( context->ctr.ctr.iv, iv, ivlen );
+		memcpy ( context->gcm.ctr.ctr.iv, iv, ivlen );
 
 	} else {
 
 		/* Calculate hash over initialisation vector */
-		gcm_process ( context, iv, NULL, ivlen, GCM_FL_IV );
-		gcm_hash ( context, &context->ctr );
-		assert ( context->len.len.add == 0 );
+		context->gcm.flags = GCM_FL_IV;
+		gcm_process ( cipher, ctx, iv, NULL, ivlen );
+		gcm_hash ( &context->gcm, &context->gcm.ctr );
+		assert ( context->gcm.len.len.add == 0 );
 
 		/* Reset non-key, non-counter state */
-		memset ( context, 0, gcm_offset ( ctr ) );
+		memset ( &context->gcm, 0, gcm_offset ( ctr ) );
 		build_assert ( gcm_offset ( ctr ) > gcm_offset ( hash ) );
 		build_assert ( gcm_offset ( ctr ) > gcm_offset ( len ) );
 		build_assert ( gcm_offset ( ctr ) < gcm_offset ( key ) );
-		build_assert ( gcm_offset ( ctr ) < gcm_offset ( raw_cipher ) );
-		build_assert ( gcm_offset ( ctr ) < gcm_offset ( raw_ctx ) );
 	}
 
 	DBGC2 ( context, "GCM %p Y[0]:\n", context );
-	DBGC2_HDA ( context, 0, &context->ctr, sizeof ( context->ctr ) );
+	DBGC2_HDA ( context, 0, &context->gcm.ctr,
+		    sizeof ( context->gcm.ctr ) );
 }
 
 /**
  * Encrypt data
  *
- * @v context		Context
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
  * @v src		Data to encrypt
  * @v dst		Buffer for encrypted data, or NULL for additional data
  * @v len		Length of data
  */
-void gcm_encrypt ( struct gcm_context *context, const void *src, void *dst,
-		   size_t len ) {
+void gcm_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+		   const void *src, void *dst, size_t len ) {
+	gcm_context_t ( cipher->ctxsize ) *context = ctx;
 
 	/* Process data */
-	gcm_process ( context, src, dst, len, GCM_FL_ENCRYPT );
+	context->gcm.flags = GCM_FL_ENCRYPT;
+	gcm_process ( cipher, ctx, src, dst, len );
 }
 
 /**
  * Decrypt data
  *
- * @v context		Context
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
  * @v src		Data to decrypt
  * @v dst		Buffer for decrypted data, or NULL for additional data
  * @v len		Length of data
  */
-void gcm_decrypt ( struct gcm_context *context, const void *src, void *dst,
-		   size_t len ) {
+void gcm_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+		   const void *src, void *dst, size_t len ) {
+	gcm_context_t ( cipher->ctxsize ) *context = ctx;
 
 	/* Process data */
-	gcm_process ( context, src, dst, len, 0 );
+	context->gcm.flags = 0;
+	gcm_process ( cipher, ctx, src, dst, len );
+}
+
+/**
+ * Generate authentication tag
+ *
+ * @v cipher		Cipher algorithm
+ * @v ctx		Context
+ * @v auth		Authentication tag
+ */
+void gcm_auth ( struct cipher_algorithm *cipher, void *ctx, void *auth ) {
+	struct cipher_algorithm *raw_cipher = cipher->priv;
+	gcm_context_t ( cipher->ctxsize ) *context = ctx;
+	union gcm_block *tag = auth;
+	union gcm_block tmp;
+	uint32_t offset;
+
+	/* Construct hash */
+	gcm_hash ( &context->gcm, tag );
+
+	/* Construct encrypted initial counter value */
+	memcpy ( &tmp, &context->gcm.ctr, sizeof ( tmp ) );
+	offset = ( ( -context->gcm.len.len.data ) / ( 8 * sizeof ( tmp ) ) );
+	gcm_count ( &tmp, offset );
+	cipher_encrypt ( raw_cipher, &context->raw, &tmp, &tmp,
+			 sizeof ( tmp ) );
+	DBGC2 ( context, "GCM %p E(K,Y[0]):\n", context );
+	DBGC2_HDA ( context, 0, &tmp, sizeof ( tmp ) );
+
+	/* Construct tag */
+	gcm_xor_block ( &tmp, tag );
+	DBGC2 ( context, "GCM %p T:\n", context );
+	DBGC2_HDA ( context, 0, tag, sizeof ( *tag ) );
 }
diff --git a/src/include/ipxe/cbc.h b/src/include/ipxe/cbc.h
index 154fc5666..11979f2e2 100644
--- a/src/include/ipxe/cbc.h
+++ b/src/include/ipxe/cbc.h
@@ -12,46 +12,21 @@ FILE_SECBOOT ( PERMITTED );
 
 #include <ipxe/crypto.h>
 
-/**
- * Set key
- *
- * @v ctx		Context
- * @v key		Key
- * @v keylen		Key length
- * @v raw_cipher	Underlying cipher algorithm
- * @v cbc_ctx		CBC context
- * @ret rc		Return status code
- */
-static inline int cbc_setkey ( void *ctx, const void *key, size_t keylen,
-			       struct cipher_algorithm *raw_cipher,
-			       void *cbc_ctx __unused ) {
-
-	return cipher_setkey ( raw_cipher, ctx, key, keylen );
-}
-
-/**
- * Set initialisation vector
- *
- * @v ctx		Context
- * @v iv		Initialisation vector
- * @v ivlen		Initialisation vector length
- * @v raw_cipher	Underlying cipher algorithm
- * @v cbc_ctx		CBC context
- */
-static inline void cbc_setiv ( void *ctx __unused,
-			       const void *iv, size_t ivlen,
-			       struct cipher_algorithm *raw_cipher,
-			       void *cbc_ctx ) {
-	assert ( ivlen == raw_cipher->blocksize );
-	memcpy ( cbc_ctx, iv, raw_cipher->blocksize );
-}
-
-extern void cbc_encrypt ( void *ctx, const void *src, void *dst,
-			  size_t len, struct cipher_algorithm *raw_cipher,
-			  void *cbc_ctx );
-extern void cbc_decrypt ( void *ctx, const void *src, void *dst,
-			  size_t len, struct cipher_algorithm *raw_cipher,
-			  void *cbc_ctx );
+/** A cipher-block chaining mode context */
+#define cbc_context_t( blocksize, ctxsize )				\
+	struct {							\
+		uint8_t cbc[ (blocksize) ];				\
+		uint8_t raw[ (ctxsize) - (blocksize) ];			\
+	}
+
+extern int cbc_setkey ( struct cipher_algorithm *cipher, void *ctx,
+			const void *key, size_t keylen );
+extern void cbc_setiv ( struct cipher_algorithm *cipher, void *ctx,
+			const void *iv, size_t ivlen );
+extern void cbc_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len );
+extern void cbc_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len );
 
 /**
  * Create a cipher-block chaining mode of behaviour of an existing cipher
@@ -64,45 +39,18 @@ extern void cbc_decrypt ( void *ctx, const void *src, void *dst,
  */
 #define CBC_CIPHER( _cbc_name, _cbc_cipher, _raw_cipher, _raw_context,	\
 		    _blocksize )					\
-struct _cbc_name ## _context {						\
-	_raw_context raw_ctx;						\
-	uint8_t cbc_ctx[_blocksize];					\
-};									\
-static int _cbc_name ## _setkey ( void *ctx, const void *key,		\
-				  size_t keylen ) {			\
-	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
-	return cbc_setkey ( &_cbc_name ## _ctx->raw_ctx, key, keylen,	\
-			    &_raw_cipher, &_cbc_name ## _ctx->cbc_ctx );\
-}									\
-static void _cbc_name ## _setiv ( void *ctx, const void *iv,		\
-				   size_t ivlen ) {			\
-	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
-	cbc_setiv ( &_cbc_name ## _ctx->raw_ctx, iv, ivlen,		\
-		    &_raw_cipher, &_cbc_name ## _ctx->cbc_ctx );	\
-}									\
-static void _cbc_name ## _encrypt ( void *ctx, const void *src,		\
-				    void *dst, size_t len ) {		\
-	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
-	cbc_encrypt ( &_cbc_name ## _ctx->raw_ctx, src, dst, len,	\
-		      &_raw_cipher, &_cbc_name ## _ctx->cbc_ctx );	\
-}									\
-static void _cbc_name ## _decrypt ( void *ctx, const void *src,		\
-				    void *dst, size_t len ) {		\
-	struct _cbc_name ## _context * _cbc_name ## _ctx = ctx;		\
-	cbc_decrypt ( &_cbc_name ## _ctx->raw_ctx, src, dst, len,	\
-		      &_raw_cipher, &_cbc_name ## _ctx->cbc_ctx );	\
-}									\
 struct cipher_algorithm _cbc_cipher = {					\
 	.name		= #_cbc_name,					\
-	.ctxsize	= sizeof ( struct _cbc_name ## _context ),	\
+	.ctxsize	= ( _blocksize + sizeof ( _raw_context ) ),	\
 	.blocksize	= _blocksize,					\
 	.alignsize	= _blocksize,					\
 	.authsize	= 0,						\
-	.setkey		= _cbc_name ## _setkey,				\
-	.setiv		= _cbc_name ## _setiv,				\
-	.encrypt	= _cbc_name ## _encrypt,			\
-	.decrypt	= _cbc_name ## _decrypt,			\
+	.setkey		= cbc_setkey,					\
+	.setiv		= cbc_setiv,					\
+	.encrypt	= cbc_encrypt,					\
+	.decrypt	= cbc_decrypt,					\
 	.auth		= cipher_null_auth,				\
+	.priv		= &_raw_cipher,					\
 };
 
 #endif /* _IPXE_CBC_H */
diff --git a/src/include/ipxe/crypto.h b/src/include/ipxe/crypto.h
index bf5bcc811..933103dfb 100644
--- a/src/include/ipxe/crypto.h
+++ b/src/include/ipxe/crypto.h
@@ -82,21 +82,26 @@ struct cipher_algorithm {
 	size_t authsize;
 	/** Set key
 	 *
+	 * @v cipher	Cipher algorithm
 	 * @v ctx	Context
 	 * @v key	Key
 	 * @v keylen	Key length
 	 * @ret rc	Return status code
 	 */
-	int ( * setkey ) ( void *ctx, const void *key, size_t keylen );
+	int ( * setkey ) ( struct cipher_algorithm *cipher, void *ctx,
+			   const void *key, size_t keylen );
 	/** Set initialisation vector
 	 *
+	 * @v cipher	Cipher algorithm
 	 * @v ctx	Context
 	 * @v iv	Initialisation vector
 	 * @v ivlen	Initialisation vector length
 	 */
-	void ( * setiv ) ( void *ctx, const void *iv, size_t ivlen );
+	void ( * setiv ) ( struct cipher_algorithm *cipher, void *ctx,
+			   const void *iv, size_t ivlen );
 	/** Encrypt data
 	 *
+	 * @v cipher	Cipher algorithm
 	 * @v ctx	Context
 	 * @v src	Data to encrypt
 	 * @v dst	Buffer for encrypted data, or NULL for additional data
@@ -104,10 +109,11 @@ struct cipher_algorithm {
 	 *
 	 * @v len is guaranteed to be a multiple of @c blocksize.
 	 */
-	void ( * encrypt ) ( void *ctx, const void *src, void *dst,
-			     size_t len );
+	void ( * encrypt ) ( struct cipher_algorithm *cipher, void *ctx,
+			     const void *src, void *dst, size_t len );
 	/** Decrypt data
 	 *
+	 * @v cipher	Cipher algorithm
 	 * @v ctx	Context
 	 * @v src	Data to decrypt
 	 * @v dst	Buffer for decrypted data, or NULL for additional data
@@ -115,14 +121,18 @@ struct cipher_algorithm {
 	 *
 	 * @v len is guaranteed to be a multiple of @c blocksize.
 	 */
-	void ( * decrypt ) ( void *ctx, const void *src, void *dst,
-			     size_t len );
+	void ( * decrypt ) ( struct cipher_algorithm *cipher, void *ctx,
+			     const void *src, void *dst, size_t len );
 	/** Generate authentication tag
 	 *
+	 * @v cipher	Cipher algorithm
 	 * @v ctx	Context
 	 * @v auth	Authentication tag
 	 */
-	void ( * auth ) ( void *ctx, void *auth );
+	void ( * auth ) ( struct cipher_algorithm *cipher, void *ctx,
+			  void *auth );
+	/** Algorithm private data */
+	void *priv;
 };
 
 /** A public key algorithm */
@@ -283,19 +293,19 @@ digest_final ( struct digest_algorithm *digest, void *ctx, void *out ) {
 static inline __attribute__ (( always_inline )) int
 cipher_setkey ( struct cipher_algorithm *cipher, void *ctx,
 		const void *key, size_t keylen ) {
-	return cipher->setkey ( ctx, key, keylen );
+	return cipher->setkey ( cipher, ctx, key, keylen );
 }
 
 static inline __attribute__ (( always_inline )) void
 cipher_setiv ( struct cipher_algorithm *cipher, void *ctx,
 	       const void *iv, size_t ivlen ) {
-	cipher->setiv ( ctx, iv, ivlen );
+	cipher->setiv ( cipher, ctx, iv, ivlen );
 }
 
 static inline __attribute__ (( always_inline )) void
 cipher_encrypt ( struct cipher_algorithm *cipher, void *ctx,
 		 const void *src, void *dst, size_t len ) {
-	cipher->encrypt ( ctx, src, dst, len );
+	cipher->encrypt ( cipher, ctx, src, dst, len );
 }
 #define cipher_encrypt( cipher, ctx, src, dst, len ) do {		\
 	assert ( ( (len) & ( (cipher)->blocksize - 1 ) ) == 0 );	\
@@ -305,7 +315,7 @@ cipher_encrypt ( struct cipher_algorithm *cipher, void *ctx,
 static inline __attribute__ (( always_inline )) void
 cipher_decrypt ( struct cipher_algorithm *cipher, void *ctx,
 		 const void *src, void *dst, size_t len ) {
-	cipher->decrypt ( ctx, src, dst, len );
+	cipher->decrypt ( cipher, ctx, src, dst, len );
 }
 #define cipher_decrypt( cipher, ctx, src, dst, len ) do {		\
 	assert ( ( (len) & ( (cipher)->blocksize - 1 ) ) == 0 );	\
@@ -314,7 +324,7 @@ cipher_decrypt ( struct cipher_algorithm *cipher, void *ctx,
 
 static inline __attribute__ (( always_inline )) void
 cipher_auth ( struct cipher_algorithm *cipher, void *ctx, void *auth ) {
-	cipher->auth ( ctx, auth );
+	cipher->auth ( cipher, ctx, auth );
 }
 
 static inline __attribute__ (( always_inline )) int
@@ -402,13 +412,16 @@ extern void digest_null_update ( struct digest_algorithm *digest, void *ctx,
 extern void digest_null_final ( struct digest_algorithm *digest, void *ctx,
 				void *out );
 
-extern int cipher_null_setkey ( void *ctx, const void *key, size_t keylen );
-extern void cipher_null_setiv ( void *ctx, const void *iv, size_t ivlen );
-extern void cipher_null_encrypt ( void *ctx, const void *src, void *dst,
-				  size_t len );
-extern void cipher_null_decrypt ( void *ctx, const void *src, void *dst,
-				  size_t len );
-extern void cipher_null_auth ( void *ctx, void *auth );
+extern int cipher_null_setkey ( struct cipher_algorithm *cipher, void *ctx,
+				const void *key, size_t keylen );
+extern void cipher_null_setiv ( struct cipher_algorithm *cipehr, void *ctx,
+				const void *iv, size_t ivlen );
+extern void cipher_null_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+				  const void *src, void *dst, size_t len );
+extern void cipher_null_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+				  const void *src, void *dst, size_t len );
+extern void cipher_null_auth ( struct cipher_algorithm *cipher, void *ctx,
+			       void *auth );
 
 extern int pubkey_null_encrypt ( const struct asn1_cursor *key,
 				 const struct asn1_cursor *plaintext,
diff --git a/src/include/ipxe/ecb.h b/src/include/ipxe/ecb.h
index c29602fca..791ab067c 100644
--- a/src/include/ipxe/ecb.h
+++ b/src/include/ipxe/ecb.h
@@ -12,13 +12,15 @@ FILE_SECBOOT ( PERMITTED );
 
 #include <ipxe/crypto.h>
 
-extern void ecb_encrypt ( void *ctx, const void *src, void *dst,
-			  size_t len, struct cipher_algorithm *raw_cipher );
-extern void ecb_decrypt ( void *ctx, const void *src, void *dst,
-			  size_t len, struct cipher_algorithm *raw_cipher );
+extern int ecb_setkey ( struct cipher_algorithm *cipher, void *ctx,
+			const void *key, size_t keylen );
+extern void ecb_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len );
+extern void ecb_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len );
 
 /**
- * Create a cipher-block chaining mode of behaviour of an existing cipher
+ * Create an electronic codebook mode of behaviour of an existing cipher
  *
  * @v _ecb_name		Name for the new ECB cipher
  * @v _ecb_cipher	New cipher algorithm
@@ -28,33 +30,18 @@ extern void ecb_decrypt ( void *ctx, const void *src, void *dst,
  */
 #define ECB_CIPHER( _ecb_name, _ecb_cipher, _raw_cipher, _raw_context,	\
 		    _blocksize )					\
-static int _ecb_name ## _setkey ( void *ctx, const void *key,		\
-				  size_t keylen ) {			\
-	return cipher_setkey ( &_raw_cipher, ctx, key, keylen );	\
-}									\
-static void _ecb_name ## _setiv ( void *ctx, const void *iv,		\
-				  size_t ivlen ) {			\
-	cipher_setiv ( &_raw_cipher, ctx, iv, ivlen );			\
-}									\
-static void _ecb_name ## _encrypt ( void *ctx, const void *src,		\
-				    void *dst, size_t len ) {		\
-	ecb_encrypt ( ctx, src, dst, len, &_raw_cipher );		\
-}									\
-static void _ecb_name ## _decrypt ( void *ctx, const void *src,		\
-				    void *dst, size_t len ) {		\
-	ecb_decrypt ( ctx, src, dst, len, &_raw_cipher );		\
-}									\
 struct cipher_algorithm _ecb_cipher = {					\
 	.name		= #_ecb_name,					\
 	.ctxsize	= sizeof ( _raw_context ),			\
 	.blocksize	= _blocksize,					\
 	.alignsize	= _blocksize,					\
 	.authsize	= 0,						\
-	.setkey		= _ecb_name ## _setkey,				\
-	.setiv		= _ecb_name ## _setiv,				\
-	.encrypt	= _ecb_name ## _encrypt,			\
-	.decrypt	= _ecb_name ## _decrypt,			\
+	.setkey		= ecb_setkey,					\
+	.setiv		= cipher_null_setiv,				\
+	.encrypt	= ecb_encrypt,					\
+	.decrypt	= ecb_decrypt,					\
 	.auth		= cipher_null_auth,				\
+	.priv		= &_raw_cipher,					\
 };
 
 #endif /* _IPXE_ECB_H */
diff --git a/src/include/ipxe/gcm.h b/src/include/ipxe/gcm.h
index 5635a1031..d794a7283 100644
--- a/src/include/ipxe/gcm.h
+++ b/src/include/ipxe/gcm.h
@@ -53,21 +53,28 @@ struct gcm_context {
 	union gcm_block ctr;
 	/** Hash key (H) */
 	union gcm_block key;
-	/** Underlying block cipher */
-	struct cipher_algorithm *raw_cipher;
-	/** Underlying block cipher context */
-	uint8_t raw_ctx[0];
+	/** Processing flags */
+	unsigned int flags;
 };
 
-extern void gcm_tag ( struct gcm_context *context, union gcm_block *tag );
-extern int gcm_setkey ( struct gcm_context *context, const void *key,
-			size_t keylen, struct cipher_algorithm *raw_cipher );
-extern void gcm_setiv ( struct gcm_context *context, const void *iv,
-			size_t ivlen );
-extern void gcm_encrypt ( struct gcm_context *context, const void *src,
-			  void *dst, size_t len );
-extern void gcm_decrypt ( struct gcm_context *context, const void *src,
-			  void *dst, size_t len );
+/** A GCM mode context */
+#define gcm_context_t( ctxsize )					\
+	struct {							\
+		struct gcm_context gcm;					\
+		uint8_t raw[ (ctxsize) -				\
+			     sizeof ( struct gcm_context ) ];		\
+	}
+
+extern int gcm_setkey ( struct cipher_algorithm *cipher, void *ctx,
+			const void *key, size_t keylen );
+extern void gcm_setiv ( struct cipher_algorithm *cipher, void *ctx,
+			const void *iv, size_t ivlen );
+extern void gcm_encrypt ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len );
+extern void gcm_decrypt ( struct cipher_algorithm *cipher, void *ctx,
+			  const void *src, void *dst, size_t len );
+extern void gcm_auth ( struct cipher_algorithm *cipher, void *ctx,
+		       void *auth );
 
 /**
  * Create a GCM mode of behaviour of an existing cipher
@@ -80,52 +87,20 @@ extern void gcm_decrypt ( struct gcm_context *context, const void *src,
  */
 #define GCM_CIPHER( _gcm_name, _gcm_cipher, _raw_cipher, _raw_context,	\
 		    _blocksize )					\
-struct _gcm_name ## _context {						\
-	/** GCM context */						\
-	struct gcm_context gcm;						\
-	/** Underlying block cipher context */				\
-	_raw_context raw;						\
-};									\
-static int _gcm_name ## _setkey ( void *ctx, const void *key,		\
-				  size_t keylen ) {			\
-	struct _gcm_name ## _context *context = ctx;			\
-	build_assert ( _blocksize == sizeof ( context->gcm.key ) );	\
-	build_assert ( offsetof ( typeof ( *context ), gcm ) == 0 );	\
-	build_assert ( offsetof ( typeof ( *context ), raw ) ==		\
-		       offsetof ( typeof ( *context ), gcm.raw_ctx ) );	\
-	return gcm_setkey ( &context->gcm, key, keylen, &_raw_cipher );	\
-}									\
-static void _gcm_name ## _setiv ( void *ctx, const void *iv,		\
-				  size_t ivlen ) {			\
-	struct _gcm_name ## _context *context = ctx;			\
-	gcm_setiv ( &context->gcm, iv, ivlen );				\
-}									\
-static void _gcm_name ## _encrypt ( void *ctx, const void *src,		\
-				    void *dst, size_t len ) {		\
-	struct _gcm_name ## _context *context = ctx;			\
-	gcm_encrypt ( &context->gcm, src, dst, len );			\
-}									\
-static void _gcm_name ## _decrypt ( void *ctx, const void *src,		\
-				    void *dst, size_t len ) {		\
-	struct _gcm_name ## _context *context = ctx;			\
-	gcm_decrypt ( &context->gcm, src, dst, len );			\
-}									\
-static void _gcm_name ## _auth ( void *ctx, void *auth ) {		\
-	struct _gcm_name ## _context *context = ctx;			\
-	union gcm_block *tag = auth;					\
-	gcm_tag ( &context->gcm, tag );					\
-}									\
+static_assert ( _blocksize == sizeof ( union gcm_block ) );		\
 struct cipher_algorithm _gcm_cipher = {					\
 	.name		= #_gcm_name,					\
-	.ctxsize	= sizeof ( struct _gcm_name ## _context ),	\
+	.ctxsize	= ( sizeof ( struct gcm_context ) +		\
+			    sizeof ( _raw_context ) ),			\
 	.blocksize	= 1,						\
 	.alignsize	= sizeof ( union gcm_block ),			\
 	.authsize	= sizeof ( union gcm_block ),			\
-	.setkey		= _gcm_name ## _setkey,				\
-	.setiv		= _gcm_name ## _setiv,				\
-	.encrypt	= _gcm_name ## _encrypt,			\
-	.decrypt	= _gcm_name ## _decrypt,			\
-	.auth		= _gcm_name ## _auth,				\
+	.setkey		= gcm_setkey,					\
+	.setiv		= gcm_setiv,					\
+	.encrypt	= gcm_encrypt,					\
+	.decrypt	= gcm_decrypt,					\
+	.auth		= gcm_auth,					\
+	.priv		= &_raw_cipher,					\
 };
 
 #endif /* _IPXE_GCM_H */