Messages in this thread | | | Subject | Re: [PATCH v2 09/25] tcp: authopt: Disable via sysctl by default | From | Leonard Crestez <> | Date | Fri, 5 Nov 2021 10:50:01 +0200 |
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On 11/3/21 4:39 AM, David Ahern wrote: > On 11/1/21 10:34 AM, Leonard Crestez wrote: >> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c >> index 97eb54774924..cc34de6e4817 100644 >> --- a/net/ipv4/sysctl_net_ipv4.c >> +++ b/net/ipv4/sysctl_net_ipv4.c >> @@ -17,10 +17,11 @@ >> #include <net/udp.h> >> #include <net/cipso_ipv4.h> >> #include <net/ping.h> >> #include <net/protocol.h> >> #include <net/netevent.h> >> +#include <net/tcp_authopt.h> >> >> static int two = 2; >> static int three __maybe_unused = 3; >> static int four = 4; >> static int thousand = 1000; >> @@ -583,10 +584,19 @@ static struct ctl_table ipv4_table[] = { >> .mode = 0644, >> .proc_handler = proc_douintvec_minmax, >> .extra1 = &sysctl_fib_sync_mem_min, >> .extra2 = &sysctl_fib_sync_mem_max, >> }, >> +#ifdef CONFIG_TCP_AUTHOPT >> + { >> + .procname = "tcp_authopt", >> + .data = &sysctl_tcp_authopt, >> + .maxlen = sizeof(int), >> + .mode = 0644, >> + .proc_handler = proc_dointvec, > > Just add it to the namespace set, and this could be a u8 (try to plug a > hole if possible) with min/max specified: > > .maxlen = sizeof(u8), > .mode = 0644, > .extra1 = SYSCTL_ZERO, > .extra2 = SYSCTL_ONE > > > see icmp_echo_enable_probe as an example. And if you are not going to > clean up when toggled off, you need a handler that tells the user it can > not be disabled by erroring out on attempts to disable it.
This is deliberately per-system because the goal is to avoid possible local privilege escalations by reducing the attack surface. Even the smallest flaw could be exploited by a malicious application establishing an authenticated connection on loopback.
Applications running in containers frequently have full access to sysctls so making this per-namespace would defeat the original purpose. I can't think of any reason to prevent using this feature at the namespace level, it has no interesting effects outside TCP connections for which it is enabled.
I also believe that as similar sysctl would be useful for TCP-MD5.
You're right about adding additional prints.
-- Regards, Leonard
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