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84b114b984
Whole point of randomization was to hide server uptime, but an attacker
can simply start a syn flood and TCP generates 'old style' timestamps,
directly revealing server jiffies value.
Also, TSval sent by the server to a particular remote address vary
depending on syncookies being sent or not, potentially triggering PAWS
drops for innocent clients.
Lets implement proper randomization, including for SYNcookies.
Also we do not need to export sysctl_tcp_timestamps, since it is not
used from a module.
In v2, I added Florian feedback and contribution, adding tsoff to
tcp_get_cookie_sock().
v3 removed one unused variable in tcp_v4_connect() as Florian spotted.
Fixes: 95a22caee3 ("tcp: randomize tcp timestamp offsets for each connection")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Tested-by: Florian Westphal <fw@strlen.de>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
21 lines
767 B
C
21 lines
767 B
C
#ifndef _NET_SECURE_SEQ
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#define _NET_SECURE_SEQ
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#include <linux/types.h>
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u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
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u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
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__be16 dport);
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u32 secure_tcp_seq(__be32 saddr, __be32 daddr,
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__be16 sport, __be16 dport);
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u32 secure_tcp_ts_off(__be32 saddr, __be32 daddr);
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u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr,
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__be16 sport, __be16 dport);
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u32 secure_tcpv6_ts_off(const __be32 *saddr, const __be32 *daddr);
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u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
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__be16 sport, __be16 dport);
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u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
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__be16 sport, __be16 dport);
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#endif /* _NET_SECURE_SEQ */
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