From eba29771c006d6a689e946fa57334a2ce370c45c Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 28 Aug 2020 10:05:08 -0700 Subject: crypto: Assume blocksize is a power of 2 The check in the encode/decode path using full division has a noticeable amount of overhead. By asserting the blocksize is a power of 2, we can reduce this check to a mask. Signed-off-by: Richard Henderson Signed-off-by: Daniel P. Berrangé --- crypto/cipher-nettle.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'crypto/cipher-nettle.c') diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c index 7e9a4cc199..0677fdfd33 100644 --- a/crypto/cipher-nettle.c +++ b/crypto/cipher-nettle.c @@ -576,6 +576,7 @@ static QCryptoCipherNettle *qcrypto_cipher_ctx_new(QCryptoCipherAlgorithm alg, QCryptoCipherAlgorithm_str(alg)); goto error; } + g_assert(is_power_of_2(ctx->blocksize)); if (mode == QCRYPTO_CIPHER_MODE_XTS && ctx->blocksize != XTS_BLOCK_SIZE) { @@ -613,7 +614,7 @@ qcrypto_nettle_cipher_encrypt(QCryptoCipher *cipher, { QCryptoCipherNettle *ctx = cipher->opaque; - if (len % ctx->blocksize) { + if (len & (ctx->blocksize - 1)) { error_setg(errp, "Length %zu must be a multiple of block size %zu", len, ctx->blocksize); return -1; @@ -666,7 +667,7 @@ qcrypto_nettle_cipher_decrypt(QCryptoCipher *cipher, { QCryptoCipherNettle *ctx = cipher->opaque; - if (len % ctx->blocksize) { + if (len & (ctx->blocksize - 1)) { error_setg(errp, "Length %zu must be a multiple of block size %zu", len, ctx->blocksize); return -1; -- cgit v1.2.3-55-g7522