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Fix XTS bug

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when input/output share the same buffer, the XTS  output will crush the last input part.
This commit is contained in:
Zhi Guan
2024-07-31 19:27:38 +08:00
parent a266042160
commit 34fa519dc0
2 changed files with 29 additions and 17 deletions
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37
src/sm4_xts.c
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@@ -51,9 +51,9 @@ int sm4_xts_encrypt(const SM4_KEY *key1, const SM4_KEY *key2, const uint8_t twea
gmssl_memxor(out, block, T, 16);
} else {
gmssl_memxor(block, in, T, 16);
sm4_encrypt(key1, block, block);
gmssl_memxor(block, block, T, 16);
gmssl_memxor(out, in, T, 16);
sm4_encrypt(key1, out, out);
gmssl_memxor(out, out, T, 16);
gf128_from_bytes(a, T);
gf128_mul_by_2(a, a);
@@ -62,12 +62,14 @@ int sm4_xts_encrypt(const SM4_KEY *key1, const SM4_KEY *key2, const uint8_t twea
in += 16;
inlen -= 16;
memcpy(out + 16, block, inlen);
memcpy(block, in, inlen);
memcpy(block, out, inlen); // backup last part of ciphertext
gmssl_memxor(block, block, T, 16);
sm4_encrypt(key1, block, block);
gmssl_memxor(out, block, T, 16);
memcpy(out, in, inlen);
gmssl_memxor(out, out, T, 16);
sm4_encrypt(key1, out, out);
gmssl_memxor(out, out, T, 16);
memcpy(out + 16, block, inlen);
}
return 1;
@@ -116,19 +118,21 @@ int sm4_xts_decrypt(const SM4_KEY *key1, const SM4_KEY *key2, const uint8_t twea
gf128_mul_by_2(a, a);
gf128_to_bytes(a, T1);
gmssl_memxor(block, in, T1, 16);
sm4_encrypt(key1, block, block);
gmssl_memxor(block, block, T1, 16);
gmssl_memxor(out, in, T1, 16);
sm4_encrypt(key1, out, out);
gmssl_memxor(out, out, T1, 16);
in += 16;
inlen -= 16;
memcpy(out + 16, block, inlen);
memcpy(block, in, inlen);
memcpy(block, out, inlen); // backup last part of plaintext
gmssl_memxor(block, block, T, 16);
sm4_encrypt(key1, block, block);
gmssl_memxor(out, block, T, 16);
memcpy(out, in, inlen);
gmssl_memxor(out, out, T, 16);
sm4_encrypt(key1, out, out);
gmssl_memxor(out, out, T, 16);
memcpy(out + 16, block, inlen);
}
return 1;
@@ -258,6 +262,7 @@ int sm4_xts_decrypt_update(SM4_XTS_CTX *ctx,
}
*outlen = 0;
if (ctx->block_nbytes) {
error_print();
left = DATA_UNIT_SIZE - ctx->block_nbytes;
if (inlen < left) {
memcpy(ctx->block + ctx->block_nbytes, in, inlen);