From d3462e378f40ba6838b6c42584c30769ca633e6f Mon Sep 17 00:00:00 2001 From: Radim Krčmář Date: Fri, 10 Jul 2015 19:18:01 +0200 Subject: crypto: avoid undefined behavior in nettle calls MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Calling a function pointer that was cast from an incompatible function results in undefined behavior. 'void *' isn't compatible with 'struct XXX *', so we can't cast to nettle_cipher_func, but have to provide a wrapper. (Conversion from 'void *' to 'struct XXX *' might require computation, which won't be done if we drop argument's true type, and pointers can have different sizes so passing arguments on stack would bug.) Having two different prototypes based on nettle version doesn't make this solution any nicer. Reported-by: Peter Maydell Signed-off-by: Radim Krčmář Message-Id: <1437062641-12684-3-git-send-email-rkrcmar@redhat.com> Signed-off-by: Paolo Bonzini --- crypto/cipher-nettle.c | 43 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c index e61aaa29f0..a55a8e8bc5 100644 --- a/crypto/cipher-nettle.c +++ b/crypto/cipher-nettle.c @@ -25,8 +25,43 @@ #if CONFIG_NETTLE_VERSION_MAJOR < 3 typedef nettle_crypt_func nettle_cipher_func; + +typedef void * cipher_ctx_t; +typedef unsigned cipher_length_t; +#else +typedef const void * cipher_ctx_t; +typedef size_t cipher_length_t; #endif +static nettle_cipher_func aes_encrypt_wrapper; +static nettle_cipher_func aes_decrypt_wrapper; +static nettle_cipher_func des_encrypt_wrapper; +static nettle_cipher_func des_decrypt_wrapper; + +static void aes_encrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length, + uint8_t *dst, const uint8_t *src) +{ + aes_encrypt(ctx, length, dst, src); +} + +static void aes_decrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length, + uint8_t *dst, const uint8_t *src) +{ + aes_encrypt(ctx, length, dst, src); +} + +static void des_encrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length, + uint8_t *dst, const uint8_t *src) +{ + des_encrypt(ctx, length, dst, src); +} + +static void des_decrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length, + uint8_t *dst, const uint8_t *src) +{ + des_decrypt(ctx, length, dst, src); +} + typedef struct QCryptoCipherNettle QCryptoCipherNettle; struct QCryptoCipherNettle { void *ctx_encrypt; @@ -87,8 +122,8 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg, des_set_key(ctx->ctx_encrypt, rfbkey); g_free(rfbkey); - ctx->alg_encrypt = (nettle_cipher_func *)des_encrypt; - ctx->alg_decrypt = (nettle_cipher_func *)des_decrypt; + ctx->alg_encrypt = des_encrypt_wrapper; + ctx->alg_decrypt = des_decrypt_wrapper; ctx->niv = DES_BLOCK_SIZE; break; @@ -102,8 +137,8 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg, aes_set_encrypt_key(ctx->ctx_encrypt, nkey, key); aes_set_decrypt_key(ctx->ctx_decrypt, nkey, key); - ctx->alg_encrypt = (nettle_cipher_func *)aes_encrypt; - ctx->alg_decrypt = (nettle_cipher_func *)aes_decrypt; + ctx->alg_encrypt = aes_encrypt_wrapper; + ctx->alg_decrypt = aes_decrypt_wrapper; ctx->niv = AES_BLOCK_SIZE; break; -- cgit v1.2.3