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

[Francis Laniel <flaniel@linux.microsoft.com>]

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@google.com>
> Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
> Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
> Signed-off-by: Mickaël Salaün <mic@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?

> +
> +		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:
> @@ -152,6 +189,13 @@ static int current_check_access_socket(struct socket
> *const sock, ARRAY_SIZE(layer_masks)))
>  		return 0;
> 
> +	audit_net.family = address->sa_family;
> +	request.audit.type = LSM_AUDIT_DATA_NET;
> +	request.audit.u.net = &audit_net;
> +	request.access = access_request;
> +	request.layer_masks = &layer_masks;
> +	request.layer_masks_size = ARRAY_SIZE(layer_masks);
> +	landlock_log_denial(dom, &request);
>  	return -EACCES;
>  }