[CRYPTO]: Fix XTEA implementation
The XTEA implementation was incorrect due to a misinterpretation of
operator precedence. Because of the wide-spread nature of this
error, the erroneous implementation will be kept, albeit under the
new name of XETA.
Signed-off-by: Aaron Grothe <ajgrothe@yahoo.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/crypto/tea.c b/crypto/tea.c
index 03c23cb..5924efd 100644
--- a/crypto/tea.c
+++ b/crypto/tea.c
@@ -1,11 +1,15 @@
/*
* Cryptographic API.
*
- * TEA and Xtended TEA Algorithms
+ * TEA, XTEA, and XETA crypto alogrithms
*
* The TEA and Xtended TEA algorithms were developed by David Wheeler
* and Roger Needham at the Computer Laboratory of Cambridge University.
*
+ * Due to the order of evaluation in XTEA many people have incorrectly
+ * implemented it. XETA (XTEA in the wrong order), exists for
+ * compatibility with these implementations.
+ *
* Copyright (c) 2004 Aaron Grothe ajgrothe@yahoo.com
*
* This program is free software; you can redistribute it and/or modify
@@ -153,9 +157,9 @@
z = u32_in (src + 4);
while (sum != limit) {
- y += (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum&3];
+ y += ((z << 4 ^ z >> 5) + z) ^ (sum + ctx->KEY[sum&3]);
sum += XTEA_DELTA;
- z += (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 &3];
+ z += ((y << 4 ^ y >> 5) + y) ^ (sum + ctx->KEY[sum>>11 &3]);
}
u32_out (dst, y);
@@ -175,6 +179,51 @@
sum = XTEA_DELTA * XTEA_ROUNDS;
while (sum) {
+ z -= ((y << 4 ^ y >> 5) + y) ^ (sum + ctx->KEY[sum>>11 & 3]);
+ sum -= XTEA_DELTA;
+ y -= ((z << 4 ^ z >> 5) + z) ^ (sum + ctx->KEY[sum & 3]);
+ }
+
+ u32_out (dst, y);
+ u32_out (dst + 4, z);
+
+}
+
+
+static void xeta_encrypt(void *ctx_arg, u8 *dst, const u8 *src)
+{
+
+ u32 y, z, sum = 0;
+ u32 limit = XTEA_DELTA * XTEA_ROUNDS;
+
+ struct xtea_ctx *ctx = ctx_arg;
+
+ y = u32_in (src);
+ z = u32_in (src + 4);
+
+ while (sum != limit) {
+ y += (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum&3];
+ sum += XTEA_DELTA;
+ z += (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 &3];
+ }
+
+ u32_out (dst, y);
+ u32_out (dst + 4, z);
+
+}
+
+static void xeta_decrypt(void *ctx_arg, u8 *dst, const u8 *src)
+{
+
+ u32 y, z, sum;
+ struct tea_ctx *ctx = ctx_arg;
+
+ y = u32_in (src);
+ z = u32_in (src + 4);
+
+ sum = XTEA_DELTA * XTEA_ROUNDS;
+
+ while (sum) {
z -= (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 & 3];
sum -= XTEA_DELTA;
y -= (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum & 3];
@@ -215,6 +264,21 @@
.cia_decrypt = xtea_decrypt } }
};
+static struct crypto_alg xeta_alg = {
+ .cra_name = "xeta",
+ .cra_flags = CRYPTO_ALG_TYPE_CIPHER,
+ .cra_blocksize = XTEA_BLOCK_SIZE,
+ .cra_ctxsize = sizeof (struct xtea_ctx),
+ .cra_module = THIS_MODULE,
+ .cra_list = LIST_HEAD_INIT(xtea_alg.cra_list),
+ .cra_u = { .cipher = {
+ .cia_min_keysize = XTEA_KEY_SIZE,
+ .cia_max_keysize = XTEA_KEY_SIZE,
+ .cia_setkey = xtea_setkey,
+ .cia_encrypt = xeta_encrypt,
+ .cia_decrypt = xeta_decrypt } }
+};
+
static int __init init(void)
{
int ret = 0;
@@ -229,6 +293,13 @@
goto out;
}
+ ret = crypto_register_alg(&xeta_alg);
+ if (ret < 0) {
+ crypto_unregister_alg(&tea_alg);
+ crypto_unregister_alg(&xtea_alg);
+ goto out;
+ }
+
out:
return ret;
}
@@ -237,12 +308,14 @@
{
crypto_unregister_alg(&tea_alg);
crypto_unregister_alg(&xtea_alg);
+ crypto_unregister_alg(&xeta_alg);
}
MODULE_ALIAS("xtea");
+MODULE_ALIAS("xeta");
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("TEA & XTEA Cryptographic Algorithms");
+MODULE_DESCRIPTION("TEA, XTEA & XETA Cryptographic Algorithms");
