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authorPhil Carmody <ext-phil.2.carmody@nokia.com>2009-07-24 01:59:17 -0400
committerHerbert Xu <herbert@gondor.apana.org.au>2009-07-24 01:59:17 -0400
commit7b4ffcf953f091a815df081911c5e75c8a38418d (patch)
tree9592ddafb6399806b3e1bbfe86333572ed782e9a /crypto/aes_generic.c
parent0044f3eda9a778ab63c2a5eafede3803f01b0b97 (diff)
crypto: aes - Undefined behaviour in crypto_aes_expand_key
It's undefined behaviour in C to write outside the bounds of an array. The key expansion routine takes a shortcut of creating 8 words at a time, but this creates 4 additional words which don't fit in the array. As everyone is hopefully now aware, GCC is at liberty to make any assumptions and optimisations it likes in situations where it can detect that UB has occured, up to and including nasal demons, and as the indices being accessed in the array are trivially calculable, it's rash to invite gcc to do take any liberties at all. Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/aes_generic.c')
-rw-r--r--crypto/aes_generic.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/crypto/aes_generic.c b/crypto/aes_generic.c
index b8b66ec3883b..e78b7ee44a74 100644
--- a/crypto/aes_generic.c
+++ b/crypto/aes_generic.c
@@ -1174,7 +1174,7 @@ EXPORT_SYMBOL_GPL(crypto_il_tab);
1174 ctx->key_enc[6 * i + 11] = t; \ 1174 ctx->key_enc[6 * i + 11] = t; \
1175} while (0) 1175} while (0)
1176 1176
1177#define loop8(i) do { \ 1177#define loop8tophalf(i) do { \
1178 t = ror32(t, 8); \ 1178 t = ror32(t, 8); \
1179 t = ls_box(t) ^ rco_tab[i]; \ 1179 t = ls_box(t) ^ rco_tab[i]; \
1180 t ^= ctx->key_enc[8 * i]; \ 1180 t ^= ctx->key_enc[8 * i]; \
@@ -1185,6 +1185,10 @@ EXPORT_SYMBOL_GPL(crypto_il_tab);
1185 ctx->key_enc[8 * i + 10] = t; \ 1185 ctx->key_enc[8 * i + 10] = t; \
1186 t ^= ctx->key_enc[8 * i + 3]; \ 1186 t ^= ctx->key_enc[8 * i + 3]; \
1187 ctx->key_enc[8 * i + 11] = t; \ 1187 ctx->key_enc[8 * i + 11] = t; \
1188} while (0)
1189
1190#define loop8(i) do { \
1191 loop8tophalf(i); \
1188 t = ctx->key_enc[8 * i + 4] ^ ls_box(t); \ 1192 t = ctx->key_enc[8 * i + 4] ^ ls_box(t); \
1189 ctx->key_enc[8 * i + 12] = t; \ 1193 ctx->key_enc[8 * i + 12] = t; \
1190 t ^= ctx->key_enc[8 * i + 5]; \ 1194 t ^= ctx->key_enc[8 * i + 5]; \
@@ -1245,8 +1249,9 @@ int crypto_aes_expand_key(struct crypto_aes_ctx *ctx, const u8 *in_key,
1245 ctx->key_enc[5] = le32_to_cpu(key[5]); 1249 ctx->key_enc[5] = le32_to_cpu(key[5]);
1246 ctx->key_enc[6] = le32_to_cpu(key[6]); 1250 ctx->key_enc[6] = le32_to_cpu(key[6]);
1247 t = ctx->key_enc[7] = le32_to_cpu(key[7]); 1251 t = ctx->key_enc[7] = le32_to_cpu(key[7]);
1248 for (i = 0; i < 7; ++i) 1252 for (i = 0; i < 6; ++i)
1249 loop8(i); 1253 loop8(i);
1254 loop8tophalf(i);
1250 break; 1255 break;
1251 } 1256 }
1252 1257