[RFC PATCH v2 12/14] landlock: Log TCP bind and connect denials

[Mickaël Salaün]

On Fri, Oct 25, 2024 at 05:25:45PM +0200, Francis Laniel wrote:
> Le mardi 22 octobre 2024, 18:10:07 CEST Mickaël Salaün a écrit :
> > Add audit support to socket_bind and socket_connect hooks.
> > 
> > Audit record sample:
> > 
> >   DENY:    domain=4533720601 blockers=net_connect_tcp daddr=127.0.0.1
> > dest=80 SYSCALL: arch=c000003e syscall=42 success=no exit=-13 ...
> > 
> > Cc: Günther Noack <gnoack at google.com>
> > Cc: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
> > Cc: Mikhail Ivanov <ivanov.mikhail1 at huawei-partners.com>
> > Signed-off-by: Mickaël Salaün <mic at digikod.net>
> > Link: https://lore.kernel.org/r/20241022161009.982584-13-mic@digikod.net
> > ---
> >  security/landlock/audit.c | 11 +++++++++
> >  security/landlock/audit.h |  1 +
> >  security/landlock/net.c   | 52 ++++++++++++++++++++++++++++++++++++---
> >  3 files changed, 60 insertions(+), 4 deletions(-)
> > 
> > diff --git a/security/landlock/audit.c b/security/landlock/audit.c
> > index 898c95ebe847..c31a4a8719ee 100644
> > --- a/security/landlock/audit.c
> > +++ b/security/landlock/audit.c
> > @@ -41,6 +41,12 @@ static const char *const fs_access_strings[] = {
> >  };
> >  static_assert(ARRAY_SIZE(fs_access_strings) == LANDLOCK_NUM_ACCESS_FS);
> > 
> > +static const char *const net_access_strings[] = {
> > +	[BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_TCP)] = "net_bind_tcp",
> > +	[BIT_INDEX(LANDLOCK_ACCESS_NET_CONNECT_TCP)] = "net_connect_tcp",
> > +};
> > +static_assert(ARRAY_SIZE(net_access_strings) == LANDLOCK_NUM_ACCESS_NET);
> > +
> >  static __attribute_const__ const char *
> >  get_blocker(const enum landlock_request_type type,
> >  	    const unsigned long access_bit)
> > @@ -58,6 +64,11 @@ get_blocker(const enum landlock_request_type type,
> >  		if (WARN_ON_ONCE(access_bit >= ARRAY_SIZE(fs_access_strings)))
> >  			return "unknown";
> >  		return fs_access_strings[access_bit];
> > +
> > +	case LANDLOCK_REQUEST_NET_ACCESS:
> > +		if (WARN_ON_ONCE(access_bit >= ARRAY_SIZE(net_access_strings)))
> > +			return "unknown";
> > +		return net_access_strings[access_bit];
> >  	}
> > 
> >  	WARN_ON_ONCE(1);
> > diff --git a/security/landlock/audit.h b/security/landlock/audit.h
> > index 320394fd6b84..1075b0c8401f 100644
> > --- a/security/landlock/audit.h
> > +++ b/security/landlock/audit.h
> > @@ -18,6 +18,7 @@ enum landlock_request_type {
> >  	LANDLOCK_REQUEST_PTRACE = 1,
> >  	LANDLOCK_REQUEST_FS_CHANGE_LAYOUT,
> >  	LANDLOCK_REQUEST_FS_ACCESS,
> > +	LANDLOCK_REQUEST_NET_ACCESS,
> >  };
> > 
> >  /*
> > diff --git a/security/landlock/net.c b/security/landlock/net.c
> > index 27872d0f7e11..c21afd6e0b4d 100644
> > --- a/security/landlock/net.c
> > +++ b/security/landlock/net.c
> > @@ -7,10 +7,12 @@
> >   */
> > 
> >  #include <linux/in.h>
> > +#include <linux/lsm_audit.h>
> >  #include <linux/net.h>
> >  #include <linux/socket.h>
> >  #include <net/ipv6.h>
> > 
> > +#include "audit.h"
> >  #include "common.h"
> >  #include "cred.h"
> >  #include "limits.h"
> > @@ -56,6 +58,10 @@ static int current_check_access_socket(struct socket
> > *const sock, };
> >  	const struct landlock_ruleset *const dom =
> >  		landlock_match_ruleset(landlock_get_current_domain(), any_net);
> > +	struct lsm_network_audit audit_net = {};
> > +	struct landlock_request request = {
> > +		.type = LANDLOCK_REQUEST_NET_ACCESS,
> > +	};
> > 
> >  	if (!dom)
> >  		return 0;
> > @@ -72,18 +78,49 @@ static int current_check_access_socket(struct socket
> > *const sock,
> > 
> >  	switch (address->sa_family) {
> >  	case AF_UNSPEC:
> > -	case AF_INET:
> > +	case AF_INET: {
> > +		const struct sockaddr_in *addr4;
> > +
> >  		if (addrlen < sizeof(struct sockaddr_in))
> >  			return -EINVAL;
> > -		port = ((struct sockaddr_in *)address)->sin_port;
> > +
> > +		addr4 = (struct sockaddr_in *)address;
> > +		port = addr4->sin_port;
> > +
> > +		if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
> > +			audit_net.dport = port;
> > +			audit_net.v4info.daddr = addr4->sin_addr.s_addr;
> > +		} else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
> > +			audit_net.sport = port;
> > +			audit_net.v4info.saddr = addr4->sin_addr.s_addr;
> > +		} else {
> > +			WARN_ON_ONCE(1);
> > +		}
> >  		break;
> > +	}
> > 
> >  #if IS_ENABLED(CONFIG_IPV6)
> > -	case AF_INET6:
> > +	case AF_INET6: {
> > +		const struct sockaddr_in6 *addr6;
> > +
> >  		if (addrlen < SIN6_LEN_RFC2133)
> >  			return -EINVAL;
> > -		port = ((struct sockaddr_in6 *)address)->sin6_port;
> > +
> > +		addr6 = (struct sockaddr_in6 *)address;
> > +		port = addr6->sin6_port;
> > +		audit_net.v6info.saddr = addr6->sin6_addr;
> 
> You set this for all access_request, but not for IPv4, is this done on 
> purpose?

Indeed, this is a bug, I'll remove this line.  Thanks!

> 
> > +
> > +		if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) {
> > +			audit_net.dport = port;
> > +			audit_net.v6info.daddr = addr6->sin6_addr;
> > +		} else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
> > +			audit_net.sport = port;
> > +			audit_net.v6info.saddr = addr6->sin6_addr;
> > +		} else {
> > +			WARN_ON_ONCE(1);
> > +		}
> >  		break;
> > +	}
> >  #endif /* IS_ENABLED(CONFIG_IPV6) */
> > 
> >  	default: