crypto: arm/aes - don't use IV buffer to return final keystream block

The ARM bit sliced AES core code uses the IV buffer to pass the final
keystream block back to the glue code if the input is not a multiple of
the block size, so that the asm code does not have to deal with anything
except 16 byte blocks. This is done under the assumption that the outgoing
IV is meaningless anyway in this case, given that chaining is no longer
possible under these circumstances.

However, as it turns out, the CCM driver does expect the IV to retain
a value that is equal to the original IV except for the counter value,
and even interprets byte zero as a length indicator, which may result
in memory corruption if the IV is overwritten with something else.

So use a separate buffer to return the final keystream block.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/arch/arm/crypto/aes-neonbs-core.S b/arch/arm/crypto/aes-neonbs-core.S
index 12da247..2b625c6 100644 (file)
--- a/arch/arm/crypto/aes-neonbs-core.S
+++ b/arch/arm/crypto/aes-neonbs-core.S
@@ -779,14 +779,15 @@ ENDPROC(aesbs_cbc_decrypt)
 
        /*
         * aesbs_ctr_encrypt(u8 out[], u8 const in[], u8 const rk[],
-        *                   int rounds, int blocks, u8 ctr[], bool final)
+        *                   int rounds, int blocks, u8 ctr[], u8 final[])
         */
 ENTRY(aesbs_ctr_encrypt)
        mov             ip, sp
        push            {r4-r10, lr}
 
        ldm             ip, {r5-r7}             // load args 4-6
-       add             r5, r5, r7              // one extra block if final == 1
+       teq             r7, #0
+       addne           r5, r5, #1              // one extra block if final != 0
 
        vld1.8          {q0}, [r6]              // load counter
        vrev32.8        q1, q0
@@ -865,19 +866,20 @@ ENTRY(aesbs_ctr_encrypt)
        veor            q2, q2, q14
        vst1.8          {q2}, [r0]!
        teq             r4, #0                  // skip last block if 'final'
-       W(bne)          4f
+       W(bne)          5f
 3:     veor            q5, q5, q15
        vst1.8          {q5}, [r0]!
 
-       next_ctr        q0
+4:     next_ctr        q0
 
        subs            r5, r5, #8
        bgt             99b
 
-       vmov            q5, q0
-
-4:     vst1.8          {q5}, [r6]
+       vst1.8          {q0}, [r6]
        pop             {r4-r10, pc}
+
+5:     vst1.8          {q5}, [r4]
+       b               4b
 ENDPROC(aesbs_ctr_encrypt)
 
        .macro          next_tweak, out, in, const, tmp

diff --git a/arch/arm/crypto/aes-neonbs-glue.c b/arch/arm/crypto/aes-neonbs-glue.c
index e262f99..2920b96 100644 (file)
--- a/arch/arm/crypto/aes-neonbs-glue.c
+++ b/arch/arm/crypto/aes-neonbs-glue.c
@@ -35,7 +35,7 @@ asmlinkage void aesbs_cbc_decrypt(u8 out[], u8 const in[], u8 const rk[],
                                  int rounds, int blocks, u8 iv[]);
 
 asmlinkage void aesbs_ctr_encrypt(u8 out[], u8 const in[], u8 const rk[],
-                                 int rounds, int blocks, u8 ctr[], bool final);
+                                 int rounds, int blocks, u8 ctr[], u8 final[]);
 
 asmlinkage void aesbs_xts_encrypt(u8 out[], u8 const in[], u8 const rk[],
                                  int rounds, int blocks, u8 iv[]);
@@ -186,6 +186,7 @@ static int ctr_encrypt(struct skcipher_request *req)
        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
        struct aesbs_ctx *ctx = crypto_skcipher_ctx(tfm);
        struct skcipher_walk walk;
+       u8 buf[AES_BLOCK_SIZE];
        int err;
 
        err = skcipher_walk_virt(&walk, req, true);
@@ -193,12 +194,12 @@ static int ctr_encrypt(struct skcipher_request *req)
        kernel_neon_begin();
        while (walk.nbytes > 0) {
                unsigned int blocks = walk.nbytes / AES_BLOCK_SIZE;
-               bool final = (walk.total % AES_BLOCK_SIZE) != 0;
+               u8 *final = (walk.total % AES_BLOCK_SIZE) ? buf : NULL;
 
                if (walk.nbytes < walk.total) {
                        blocks = round_down(blocks,
                                            walk.stride / AES_BLOCK_SIZE);
-                       final = false;
+                       final = NULL;
                }
 
                aesbs_ctr_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
@@ -210,7 +211,7 @@ static int ctr_encrypt(struct skcipher_request *req)
 
                        if (dst != src)
                                memcpy(dst, src, walk.total % AES_BLOCK_SIZE);
-                       crypto_xor(dst, walk.iv, walk.total % AES_BLOCK_SIZE);
+                       crypto_xor(dst, final, walk.total % AES_BLOCK_SIZE);
 
                        err = skcipher_walk_done(&walk, 0);
                        break;