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commit 0fb1a617a07b8df5de188dd5a0c8bf293d4bfc0e
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Author: markus@openbsd.org <markus@openbsd.org>
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Date:   Sat Mar 11 13:07:35 2017 +0000
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    upstream commit
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    Don't count the initial block twice when computing how
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    many bytes to discard for the work around for the attacks against CBC-mode.
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    ok djm@; report from Jean Paul, Kenny, Martin and Torben @ RHUL
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    Upstream-ID: f445f509a4e0a7ba3b9c0dae7311cb42458dc1e2
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diff --git a/packet.c b/packet.c
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index 01e2d45..2f3a2ec 100644
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--- a/packet.c
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+++ b/packet.c
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@@ -1850,11 +1850,11 @@ ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
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 			if (r != SSH_ERR_MAC_INVALID)
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 				goto out;
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 			logit("Corrupted MAC on input.");
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-			if (need > PACKET_MAX_SIZE)
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+			if (need + block_size > PACKET_MAX_SIZE)
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 				return SSH_ERR_INTERNAL_ERROR;
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 			return ssh_packet_start_discard(ssh, enc, mac,
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 			    sshbuf_len(state->incoming_packet),
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-			    PACKET_MAX_SIZE - need);
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+			    PACKET_MAX_SIZE - need - block_size);
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 		}
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 		/* Remove MAC from input buffer */
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 		DBG(debug("MAC #%d ok", state->p_read.seqnr));