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fscrypt: write CBC-CTS instead of CTS-CBC

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Calling CBC with ciphertext stealing "CBC-CTS" seems to be more common
than calling it "CTS-CBC".  E.g., CBC-CTS is used by OpenSSL, Crypto++,
RFC3962, and RFC6803.  The NIST SP800-38A addendum uses CBC-CS1,
CBC-CS2, and CBC-CS3, distinguishing between different CTS conventions
but similarly putting the CBC part first.  In the interest of avoiding
any idiosyncratic terminology, update the fscrypt documentation and the
fscrypt_mode "friendly names" to align with the more common convention.

Changing the "friendly names" only affects some log messages.  The
actual mode constants in the API are unchanged; those call it simply
"CTS".  Add a note to the documentation that clarifies that "CBC" and
"CTS" in the API really mean CBC-ESSIV and CBC-CTS, respectively.

Link: https://lore.kernel.org/r/20240224053550.44659-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers
2024-02-23 21:35:49 -08:00
parent d3a7bd4200
commit 2f944c66ae
2 changed files with 18 additions and 15 deletions
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6
fs/crypto/keysetup.c
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@@ -23,7 +23,7 @@ struct fscrypt_mode fscrypt_modes[] = {
.blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
},
[FSCRYPT_MODE_AES_256_CTS] = {
.friendly_name = "AES-256-CTS-CBC",
.friendly_name = "AES-256-CBC-CTS",
.cipher_str = "cts(cbc(aes))",
.keysize = 32,
.security_strength = 32,
@@ -38,7 +38,7 @@ struct fscrypt_mode fscrypt_modes[] = {
.blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
},
[FSCRYPT_MODE_AES_128_CTS] = {
.friendly_name = "AES-128-CTS-CBC",
.friendly_name = "AES-128-CBC-CTS",
.cipher_str = "cts(cbc(aes))",
.keysize = 16,
.security_strength = 16,
@@ -53,7 +53,7 @@ struct fscrypt_mode fscrypt_modes[] = {
.blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,
},
[FSCRYPT_MODE_SM4_CTS] = {
.friendly_name = "SM4-CTS-CBC",
.friendly_name = "SM4-CBC-CTS",
.cipher_str = "cts(cbc(sm4))",
.keysize = 16,
.security_strength = 16,