AES: Extend key wrap implementation to support longer data

This extends the "XOR t" operation in aes_wrap() and aes_unwrap() to
handle up to four octets of the n*h+i value instead of just the least
significant octet. This allows the plaintext be longer than 336 octets
which was the previous limit.

Signed-off-by: Jouni Malinen <j@w1.fi>

diff --git a/src/crypto/aes-unwrap.c b/src/crypto/aes-unwrap.c
index c2b46b7..ec793d9 100644 (file)
--- a/src/crypto/aes-unwrap.c
+++ b/src/crypto/aes-unwrap.c
@@ -29,6 +29,7 @@ int aes_unwrap(const u8 *kek, size_t kek_len, int n, const u8 *cipher,
        u8 a[8], *r, b[AES_BLOCK_SIZE];
        int i, j;
        void *ctx;
+       unsigned int t;
 
        /* 1) Initialize variables. */
        os_memcpy(a, cipher, 8);
@@ -50,7 +51,11 @@ int aes_unwrap(const u8 *kek, size_t kek_len, int n, const u8 *cipher,
                r = plain + (n - 1) * 8;
                for (i = n; i >= 1; i--) {
                        os_memcpy(b, a, 8);
-                       b[7] ^= n * j + i;
+                       t = n * j + i;
+                       b[7] ^= t;
+                       b[6] ^= t >> 8;
+                       b[5] ^= t >> 16;
+                       b[4] ^= t >> 24;
 
                        os_memcpy(b + 8, r, 8);
                        aes_decrypt(ctx, b, b);

diff --git a/src/crypto/aes-wrap.c b/src/crypto/aes-wrap.c
index f72437a..7ed34e8 100644 (file)
--- a/src/crypto/aes-wrap.c
+++ b/src/crypto/aes-wrap.c
@@ -28,6 +28,7 @@ int aes_wrap(const u8 *kek, size_t kek_len, int n, const u8 *plain, u8 *cipher)
        u8 *a, *r, b[AES_BLOCK_SIZE];
        int i, j;
        void *ctx;
+       unsigned int t;
 
        a = cipher;
        r = cipher + 8;
@@ -54,7 +55,11 @@ int aes_wrap(const u8 *kek, size_t kek_len, int n, const u8 *plain, u8 *cipher)
                        os_memcpy(b + 8, r, 8);
                        aes_encrypt(ctx, b, b);
                        os_memcpy(a, b, 8);
-                       a[7] ^= n * j + i;
+                       t = n * j + i;
+                       a[7] ^= t;
+                       a[6] ^= t >> 8;
+                       a[5] ^= t >> 16;
+                       a[4] ^= t >> 24;
                        os_memcpy(r, b + 8, 8);
                        r += 8;
                }