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crypto: avoid undefined behavior in nettle calls 

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 <peter.maydell@linaro.org>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Message-Id: <1437062641-12684-3-git-send-email-rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Radim Krčmář 2015-07-10 19:18:01 +02:00 committed by Paolo Bonzini
parent becaeb726a
commit d3462e378f
1 changed files with 39 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
crypto/cipher-nettle.c
View File

@ -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;