crypto: Add aesdec_ISB_ISR_AK

Add a primitive for InvSubBytes + InvShiftRows + AddRoundKey.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/crypto/aes.c b/crypto/aes.c
index 408d92b81f..90274c3706 100644
--- a/crypto/aes.c
+++ b/crypto/aes.c
@@ -1261,6 +1261,51 @@ void aesenc_SB_SR_AK_genrev(AESState *r, const AESState *s, const AESState *k)
     aesenc_SB_SR_AK_swap(r, s, k, true);
 }
 
+/*
+ * Perform InvSubBytes + InvShiftRows + AddRoundKey.
+ */
+static inline void
+aesdec_ISB_ISR_AK_swap(AESState *ret, const AESState *st,
+                       const AESState *rk, bool swap)
+{
+    const int swap_b = swap ? 15 : 0;
+    AESState t;
+
+    t.b[swap_b ^ 0x0] = AES_isbox[st->b[swap_b ^ AES_ISH(0x0)]];
+    t.b[swap_b ^ 0x1] = AES_isbox[st->b[swap_b ^ AES_ISH(0x1)]];
+    t.b[swap_b ^ 0x2] = AES_isbox[st->b[swap_b ^ AES_ISH(0x2)]];
+    t.b[swap_b ^ 0x3] = AES_isbox[st->b[swap_b ^ AES_ISH(0x3)]];
+    t.b[swap_b ^ 0x4] = AES_isbox[st->b[swap_b ^ AES_ISH(0x4)]];
+    t.b[swap_b ^ 0x5] = AES_isbox[st->b[swap_b ^ AES_ISH(0x5)]];
+    t.b[swap_b ^ 0x6] = AES_isbox[st->b[swap_b ^ AES_ISH(0x6)]];
+    t.b[swap_b ^ 0x7] = AES_isbox[st->b[swap_b ^ AES_ISH(0x7)]];
+    t.b[swap_b ^ 0x8] = AES_isbox[st->b[swap_b ^ AES_ISH(0x8)]];
+    t.b[swap_b ^ 0x9] = AES_isbox[st->b[swap_b ^ AES_ISH(0x9)]];
+    t.b[swap_b ^ 0xa] = AES_isbox[st->b[swap_b ^ AES_ISH(0xA)]];
+    t.b[swap_b ^ 0xb] = AES_isbox[st->b[swap_b ^ AES_ISH(0xB)]];
+    t.b[swap_b ^ 0xc] = AES_isbox[st->b[swap_b ^ AES_ISH(0xC)]];
+    t.b[swap_b ^ 0xd] = AES_isbox[st->b[swap_b ^ AES_ISH(0xD)]];
+    t.b[swap_b ^ 0xe] = AES_isbox[st->b[swap_b ^ AES_ISH(0xE)]];
+    t.b[swap_b ^ 0xf] = AES_isbox[st->b[swap_b ^ AES_ISH(0xF)]];
+
+    /*
+     * Perform the AddRoundKey with generic vectors.
+     * This may be expanded to either host integer or host vector code.
+     * The key and output endianness match, so no bswap required.
+     */
+    ret->v = t.v ^ rk->v;
+}
+
+void aesdec_ISB_ISR_AK_gen(AESState *r, const AESState *s, const AESState *k)
+{
+    aesdec_ISB_ISR_AK_swap(r, s, k, false);
+}
+
+void aesdec_ISB_ISR_AK_genrev(AESState *r, const AESState *s, const AESState *k)
+{
+    aesdec_ISB_ISR_AK_swap(r, s, k, true);
+}
+
 /**
  * Expand the cipher key into the encryption key schedule.
  */