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From 32cc2479b473c49ce869e57fded7e9a77b695c0d Mon Sep 17 00:00:00 2001
From: "Dr. Stephen Henson" <steve@openssl.org>
Date: Thu, 7 Feb 2013 21:06:37 +0000
Subject: [PATCH] Fix IV check and padding removal.
Fix the calculation that checks there is enough room in a record
after removing padding and optional explicit IV. (by Steve)
For AEAD remove the correct number of padding bytes (by Andy)
---
ssl/s3_cbc.c | 33 ++++++++++++---------------------
1 file changed, 12 insertions(+), 21 deletions(-)
diff --git a/ssl/s3_cbc.c b/ssl/s3_cbc.c
index ce77acd..0f60507 100644
--- a/ssl/s3_cbc.c
+++ b/ssl/s3_cbc.c
@@ -139,31 +139,22 @@ int tls1_cbc_remove_padding(const SSL* s,
unsigned mac_size)
{
unsigned padding_length, good, to_check, i;
- const char has_explicit_iv =
- s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION;
- const unsigned overhead = 1 /* padding length byte */ +
- mac_size +
- (has_explicit_iv ? block_size : 0);
-
- /* These lengths are all public so we can test them in non-constant
- * time. */
- if (overhead > rec->length)
- return 0;
-
- /* We can always safely skip the explicit IV. We check at the beginning
- * of this function that the record has at least enough space for the
- * IV, MAC and padding length byte. (These can be checked in
- * non-constant time because it's all public information.) So, if the
- * padding was invalid, then we didn't change |rec->length| and this is
- * safe. If the padding was valid then we know that we have at least
- * overhead+padding_length bytes of space and so this is still safe
- * because overhead accounts for the explicit IV. */
- if (has_explicit_iv)
+ const unsigned overhead = 1 /* padding length byte */ + mac_size;
+ /* Check if version requires explicit IV */
+ if (s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION)
{
+ /* These lengths are all public so we can test them in
+ * non-constant time.
+ */
+ if (overhead + block_size > rec->length)
+ return 0;
+ /* We can now safely skip explicit IV */
rec->data += block_size;
rec->input += block_size;
rec->length -= block_size;
}
+ else if (overhead > rec->length)
+ return 0;
padding_length = rec->data[rec->length-1];
@@ -190,7 +181,7 @@ int tls1_cbc_remove_padding(const SSL* s,
if (EVP_CIPHER_flags(s->enc_read_ctx->cipher)&EVP_CIPH_FLAG_AEAD_CIPHER)
{
/* padding is already verified */
- rec->length -= padding_length;
+ rec->length -= padding_length + 1;
return 1;
}
--
1.8.1.2
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