From: Eric Biggers <ebiggers@xxxxxxxxxx>
The AES library code (which originally came from crypto/aes_ti.c) is
supposed to be constant-time, to the extent possible for a C
implementation. But the hardening measure of disabling interrupts while
the S-box is loaded into cache was not included in the library version;
it was left only in the crypto API wrapper in crypto/aes_ti.c.
Move this logic into the library version so that everyone gets it.
Fixes: e59c1c987456 ("crypto: aes - create AES library based on the fixed time AES code")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.4+
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
crypto/aes_ti.c | 18 ------------------
lib/crypto/aes.c | 18 ++++++++++++++++++
2 files changed, 18 insertions(+), 18 deletions(-)
diff --git a/crypto/aes_ti.c b/crypto/aes_ti.c
index 205c2c257d4926..121f36621d6dcf 100644
--- a/crypto/aes_ti.c
+++ b/crypto/aes_ti.c
@@ -20,33 +20,15 @@ static int aesti_set_key(struct crypto_tfm *tfm, const u8 *in_key,
static void aesti_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
- unsigned long flags;
-
- /*
- * Temporarily disable interrupts to avoid races where cachelines are
- * evicted when the CPU is interrupted to do something else.
- */
- local_irq_save(flags);
aes_encrypt(ctx, out, in);
-
- local_irq_restore(flags);
}
static void aesti_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
const struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
- unsigned long flags;
-
- /*
- * Temporarily disable interrupts to avoid races where cachelines are
- * evicted when the CPU is interrupted to do something else.
- */
- local_irq_save(flags);
aes_decrypt(ctx, out, in);
-
- local_irq_restore(flags);
}
static struct crypto_alg aes_alg = {
diff --git a/lib/crypto/aes.c b/lib/crypto/aes.c
index 827fe89922fff0..029d8d0eac1f6e 100644
--- a/lib/crypto/aes.c
+++ b/lib/crypto/aes.c
@@ -260,6 +260,7 @@ void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
const u32 *rkp = ctx->key_enc + 4;
int rounds = 6 + ctx->key_length / 4;
u32 st0[4], st1[4];
+ unsigned long flags;
int round;
st0[0] = ctx->key_enc[0] ^ get_unaligned_le32(in);
@@ -267,6 +268,12 @@ void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
st0[2] = ctx->key_enc[2] ^ get_unaligned_le32(in + 8);
st0[3] = ctx->key_enc[3] ^ get_unaligned_le32(in + 12);
+ /*
+ * Temporarily disable interrupts to avoid races where cachelines are
+ * evicted when the CPU is interrupted to do something else.
+ */
+ local_irq_save(flags);
+
/*
* Force the compiler to emit data independent Sbox references,
* by xoring the input with Sbox values that are known to add up
@@ -297,6 +304,8 @@ void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
put_unaligned_le32(subshift(st1, 1) ^ rkp[5], out + 4);
put_unaligned_le32(subshift(st1, 2) ^ rkp[6], out + 8);
put_unaligned_le32(subshift(st1, 3) ^ rkp[7], out + 12);
+
+ local_irq_restore(flags);
}
EXPORT_SYMBOL(aes_encrypt);
@@ -311,6 +320,7 @@ void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
const u32 *rkp = ctx->key_dec + 4;
int rounds = 6 + ctx->key_length / 4;
u32 st0[4], st1[4];
+ unsigned long flags;
int round;
st0[0] = ctx->key_dec[0] ^ get_unaligned_le32(in);
@@ -318,6 +328,12 @@ void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
st0[2] = ctx->key_dec[2] ^ get_unaligned_le32(in + 8);
st0[3] = ctx->key_dec[3] ^ get_unaligned_le32(in + 12);
+ /*
+ * Temporarily disable interrupts to avoid races where cachelines are
+ * evicted when the CPU is interrupted to do something else.
+ */
+ local_irq_save(flags);
+
/*
* Force the compiler to emit data independent Sbox references,
* by xoring the input with Sbox values that are known to add up
@@ -348,6 +364,8 @@ void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in)
put_unaligned_le32(inv_subshift(st1, 1) ^ rkp[5], out + 4);
put_unaligned_le32(inv_subshift(st1, 2) ^ rkp[6], out + 8);
put_unaligned_le32(inv_subshift(st1, 3) ^ rkp[7], out + 12);
+
+ local_irq_restore(flags);
}
EXPORT_SYMBOL(aes_decrypt);
--
2.26.2
