47 lines
1.7 KiB
Diff
47 lines
1.7 KiB
Diff
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From df943912046aee2e5e541949dbdbafa38819f195 Mon Sep 17 00:00:00 2001
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From: Matt Caswell <matt@openssl.org>
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Date: Fri, 8 May 2020 11:12:10 +0100
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Subject: [PATCH 050/217] Correct alignment calculation in ssl3_setup_write
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The alignment calculation in ssl3_setup_write incorrectly results in an
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alignment allowance of
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(-SSL3_RT_HEADER_LENGTH) & (SSL3_ALIGN_PAYLOAD - 1) bytes. This equals 3
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in almost all cases. The maximum alignment actually used in do_ssl3_write
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is (SSL3_ALIGN_PAYLOAD - 1). This equals 7 bytes in almost all cases. So
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there is a potential to overrun the buffer by up to 4 bytes.
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Fortunately, the encryption overhead allowed for is 80 bytes which
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consists of 16 bytes for the cipher block size and 64 bytes for the MAC
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output. However the biggest MAC that we ever produce is HMAC-384 which is
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48 bytes - so we have a headroom of 16 bytes (i.e. more than the 4 bytes
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of potential overrun).
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Thanks to Nagesh Hegde for reporting this.
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Fixes #11766
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Reviewed-by: Ben Kaduk <kaduk@mit.edu>
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(Merged from https://github.com/openssl/openssl/pull/11768)
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(cherry picked from commit d30ef639647ad263d09740c931a5bfb5a8b6a5f6)
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---
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ssl/record/ssl3_buffer.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/ssl/record/ssl3_buffer.c b/ssl/record/ssl3_buffer.c
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index 605f8f9..56c0d78 100644
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--- a/ssl/record/ssl3_buffer.c
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+++ b/ssl/record/ssl3_buffer.c
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@@ -94,7 +94,7 @@ int ssl3_setup_write_buffer(SSL *s, size_t numwpipes, size_t len)
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headerlen = SSL3_RT_HEADER_LENGTH;
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#if defined(SSL3_ALIGN_PAYLOAD) && SSL3_ALIGN_PAYLOAD!=0
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- align = (-SSL3_RT_HEADER_LENGTH) & (SSL3_ALIGN_PAYLOAD - 1);
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+ align = SSL3_ALIGN_PAYLOAD - 1;
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#endif
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len = ssl_get_max_send_fragment(s)
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--
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1.8.3.1
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