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[crypto] Allow creation of arbitrary CBC cipher algorithms using CBC_…
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…CIPHER()

Given any block cipher, a corresponding CBC mode of behaviour for the
cipher can be created using the CBC_CIPHER() macro.
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Michael Brown committed Feb 19, 2009
1 parent e950dc0 commit 9937bf1
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Showing 3 changed files with 66 additions and 106 deletions.
92 changes: 2 additions & 90 deletions src/crypto/axtls_aes.c
View file
Expand Up @@ -33,13 +33,6 @@
/** Basic AES blocksize */
#define AES_BLOCKSIZE 16

/****************************************************************************
*
* Basic AES algorithm (independent of mode of operation)
*
****************************************************************************
*/

/** AES context */
struct aes_context {
/** AES context for AXTLS */
Expand Down Expand Up @@ -169,87 +162,6 @@ static struct cipher_algorithm aes_algorithm = {
.decrypt = aes_decrypt,
};

/****************************************************************************
*
* AES with cipher-block chaining (CBC)
*
****************************************************************************
*/

/** AES with CBC context */
struct aes_cbc_context {
/** AES context */
struct aes_context aes_ctx;
/** CBC context */
uint8_t cbc_ctx[AES_BLOCKSIZE];
};

/**
* Set key
*
* @v ctx Context
* @v key Key
* @v keylen Key length
* @ret rc Return status code
*/
static int aes_cbc_setkey ( void *ctx, const void *key, size_t keylen ) {
struct aes_cbc_context *aes_cbc_ctx = ctx;

return cbc_setkey ( ctx, key, keylen, &aes_algorithm,
&aes_cbc_ctx->cbc_ctx );
}

/**
* Set initialisation vector
*
* @v ctx Context
* @v iv Initialisation vector
*/
static void aes_cbc_setiv ( void *ctx, const void *iv ) {
struct aes_cbc_context *aes_cbc_ctx = ctx;

cbc_setiv ( ctx, iv, &aes_algorithm, &aes_cbc_ctx->cbc_ctx );
}

/**
* Encrypt data
*
* @v ctx Context
* @v src Data to encrypt
* @v dst Buffer for encrypted data
* @v len Length of data
*/
static void aes_cbc_encrypt ( void *ctx, const void *src, void *dst,
size_t len ) {
struct aes_cbc_context *aes_cbc_ctx = ctx;

cbc_encrypt ( &aes_cbc_ctx->aes_ctx, src, dst, len,
&aes_algorithm, &aes_cbc_ctx->cbc_ctx );
}

/**
* Decrypt data
*
* @v ctx Context
* @v src Data to decrypt
* @v dst Buffer for decrypted data
* @v len Length of data
*/
static void aes_cbc_decrypt ( void *ctx, const void *src, void *dst,
size_t len ) {
struct aes_cbc_context *aes_cbc_ctx = ctx;

cbc_decrypt ( &aes_cbc_ctx->aes_ctx, src, dst, len,
&aes_algorithm, &aes_cbc_ctx->cbc_ctx );
}

/* AES with cipher-block chaining */
struct cipher_algorithm aes_cbc_algorithm = {
.name = "aes_cbc",
.ctxsize = sizeof ( struct aes_cbc_context ),
.blocksize = AES_BLOCKSIZE,
.setkey = aes_cbc_setkey,
.setiv = aes_cbc_setiv,
.encrypt = aes_cbc_encrypt,
.decrypt = aes_cbc_decrypt,
};
CBC_CIPHER ( aes_cbc, aes_cbc_algorithm,
aes_algorithm, struct aes_context, AES_BLOCKSIZE );
16 changes: 8 additions & 8 deletions src/crypto/cbc.c
View file
Expand Up @@ -53,18 +53,18 @@ static void cbc_xor ( const void *src, void *dst, size_t len ) {
* @v src Data to encrypt
* @v dst Buffer for encrypted data
* @v len Length of data
* @v cipher Underlying cipher algorithm
* @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 *cipher, void *cbc_ctx ) {
size_t blocksize = cipher->blocksize;
struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
size_t blocksize = raw_cipher->blocksize;

assert ( ( len % blocksize ) == 0 );

while ( len ) {
cbc_xor ( src, cbc_ctx, blocksize );
cipher_encrypt ( cipher, ctx, cbc_ctx, dst, blocksize );
cipher_encrypt ( raw_cipher, ctx, cbc_ctx, dst, blocksize );
memcpy ( cbc_ctx, dst, blocksize );
dst += blocksize;
src += blocksize;
Expand All @@ -79,17 +79,17 @@ void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
* @v src Data to decrypt
* @v dst Buffer for decrypted data
* @v len Length of data
* @v cipher Underlying cipher algorithm
* @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 *cipher, void *cbc_ctx ) {
size_t blocksize = cipher->blocksize;
struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
size_t blocksize = raw_cipher->blocksize;

assert ( ( len % blocksize ) == 0 );

while ( len ) {
cipher_decrypt ( cipher, ctx, src, dst, blocksize );
cipher_decrypt ( raw_cipher, ctx, src, dst, blocksize );
cbc_xor ( cbc_ctx, dst, blocksize );
memcpy ( cbc_ctx, src, blocksize );
dst += blocksize;
Expand Down
64 changes: 56 additions & 8 deletions src/include/gpxe/cbc.h
View file
Expand Up @@ -15,36 +15,84 @@
* @v ctx Context
* @v key Key
* @v keylen Key length
* @v cipher Underlying cipher algorithm
* @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 *cipher,
struct cipher_algorithm *raw_cipher,
void *cbc_ctx __unused ) {

return cipher_setkey ( cipher, ctx, key, keylen );
return cipher_setkey ( raw_cipher, ctx, key, keylen );
}

/**
* Set initialisation vector
*
* @v ctx Context
* @v iv Initialisation vector
* @v cipher Underlying cipher algorithm
* @v raw_cipher Underlying cipher algorithm
* @v cbc_ctx CBC context
*/
static inline void cbc_setiv ( void *ctx __unused, const void *iv,
struct cipher_algorithm *cipher,
struct cipher_algorithm *raw_cipher,
void *cbc_ctx ) {
memcpy ( cbc_ctx, iv, 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 *cipher,
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 *cipher,
size_t len, struct cipher_algorithm *raw_cipher,
void *cbc_ctx );

/**
* Create a cipher-block chaining mode of behaviour of an existing cipher
*
* @v _cbc_name Name for the new CBC cipher
* @v _cbc_cipher New cipher algorithm
* @v _raw_cipher Underlying cipher algorithm
* @v _raw_context Context structure for the underlying cipher
* @v _blocksize Cipher block size
*/
#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 ) { \
struct _cbc_name ## _context * _cbc_name ## _ctx = ctx; \
cbc_setiv ( &_cbc_name ## _ctx->raw_ctx, iv, \
&_raw_cipher, &aes_cbc_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, &aes_cbc_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, &aes_cbc_ctx->cbc_ctx ); \
} \
struct cipher_algorithm _cbc_cipher = { \
.name = #_cbc_name, \
.ctxsize = sizeof ( struct _cbc_name ## _context ), \
.blocksize = _blocksize, \
.setkey = _cbc_name ## _setkey, \
.setiv = _cbc_name ## _setiv, \
.encrypt = _cbc_name ## _encrypt, \
.decrypt = _cbc_name ## _decrypt, \
};

#endif /* _GPXE_CBC_H */

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