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Date: Mon, 28 Nov 2022 11:21:36 +0300 From: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com> To: Mickaël Salaün <mic@...ikod.net> CC: <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>, <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>, <artem.kuzin@...wei.com>, <linux-api@...r.kernel.org>, "Alejandro Colomar (man-pages)" <alx.manpages@...il.com> Subject: Re: [PATCH v8 08/12] landlock: Implement TCP network hooks 11/17/2022 9:43 PM, Mickaël Salaün пишет: > > On 21/10/2022 17:26, Konstantin Meskhidze wrote: >> This patch adds support of socket_bind() and socket_connect() hooks. >> It's possible to restrict binding and connecting of TCP sockets to >> particular ports. > > Implement socket_bind() and socket_connect LSM hooks, which enable to > restrict TCP socket binding and connection to specific ports. > Ok. Thanks. > >> >> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com> >> --- >> >> Changes since v7: >> * Minor fixes. >> * Refactors commit message. >> >> Changes since v6: >> * Updates copyright. >> * Refactors landlock_append_net_rule() and check_socket_access() >> functions with landlock_id type. >> >> Changes since v5: >> * Fixes some logic errors. >> * Formats code with clang-format-14. >> >> Changes since v4: >> * Factors out CONFIG_INET into make file. >> * Refactors check_socket_access(). >> * Adds helper get_port(). >> * Adds CONFIG_IPV6 in get_port(), hook_socket_bind/connect >> functions to support AF_INET6 family. >> * Adds AF_UNSPEC family support in hook_socket_bind/connect >> functions. >> * Refactors add_rule_net_service() and landlock_add_rule >> syscall to support network rule inserting. >> * Refactors init_layer_masks() to support network rules. >> >> Changes since v3: >> * Splits commit. >> * Adds SECURITY_NETWORK in config. >> * Adds IS_ENABLED(CONFIG_INET) if a kernel has no INET configuration. >> * Adds hook_socket_bind and hook_socket_connect hooks. >> >> --- >> security/landlock/Kconfig | 1 + >> security/landlock/Makefile | 2 + >> security/landlock/net.c | 164 +++++++++++++++++++++++++++++++++++ >> security/landlock/net.h | 26 ++++++ >> security/landlock/setup.c | 2 + >> security/landlock/syscalls.c | 59 ++++++++++++- >> 6 files changed, 251 insertions(+), 3 deletions(-) >> create mode 100644 security/landlock/net.c >> create mode 100644 security/landlock/net.h >> >> diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig >> index 8e33c4e8ffb8..10c099097533 100644 >> --- a/security/landlock/Kconfig >> +++ b/security/landlock/Kconfig >> @@ -3,6 +3,7 @@ >> config SECURITY_LANDLOCK >> bool "Landlock support" >> depends on SECURITY && !ARCH_EPHEMERAL_INODES >> + select SECURITY_NETWORK >> select SECURITY_PATH >> help >> Landlock is a sandboxing mechanism that enables processes to restrict >> diff --git a/security/landlock/Makefile b/security/landlock/Makefile >> index 7bbd2f413b3e..53d3c92ae22e 100644 >> --- a/security/landlock/Makefile >> +++ b/security/landlock/Makefile >> @@ -2,3 +2,5 @@ obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o >> >> landlock-y := setup.o syscalls.o object.o ruleset.o \ >> cred.o ptrace.o fs.o >> + >> +landlock-$(CONFIG_INET) += net.o >> \ No newline at end of file >> diff --git a/security/landlock/net.c b/security/landlock/net.c >> new file mode 100644 >> index 000000000000..39e8a156a1f4 >> --- /dev/null >> +++ b/security/landlock/net.c >> @@ -0,0 +1,164 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * Landlock LSM - Network management and hooks >> + * >> + * Copyright © 2022 Huawei Tech. Co., Ltd. >> + * Copyright © 2022 Microsoft Corporation >> + */ >> + >> +#include <linux/in.h> >> +#include <linux/net.h> >> +#include <linux/socket.h> >> +#include <net/ipv6.h> >> + >> +#include "common.h" >> +#include "cred.h" >> +#include "limits.h" >> +#include "net.h" >> +#include "ruleset.h" >> + >> +int landlock_append_net_rule(struct landlock_ruleset *const ruleset, >> + const u16 port, access_mask_t access_rights) >> +{ >> + int err; >> + const struct landlock_id id = { >> + .key.data = port, >> + .type = LANDLOCK_KEY_NET_PORT, >> + }; >> + BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data)); >> + >> + /* Transforms relative access rights to absolute ones. */ >> + access_rights |= LANDLOCK_MASK_ACCESS_NET & >> + ~landlock_get_net_access_mask(ruleset, 0); >> + >> + mutex_lock(&ruleset->lock); >> + err = landlock_insert_rule(ruleset, id, access_rights); >> + mutex_unlock(&ruleset->lock); >> + >> + return err; >> +} >> + >> +static int check_socket_access(const struct landlock_ruleset *const domain, >> + u16 port, access_mask_t access_request) >> +{ >> + bool allowed = false; >> + layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {}; >> + const struct landlock_rule *rule; >> + access_mask_t handled_access; >> + const struct landlock_id id = { >> + .key.data = port, >> + .type = LANDLOCK_KEY_NET_PORT, >> + }; >> + >> + if (WARN_ON_ONCE(!domain)) >> + return 0; >> + if (WARN_ON_ONCE(domain->num_layers < 1)) >> + return -EACCES; >> + >> + rule = landlock_find_rule(domain, id); >> + handled_access = init_layer_masks(domain, access_request, &layer_masks, >> + LANDLOCK_KEY_NET_PORT); >> + allowed = unmask_layers(rule, handled_access, &layer_masks, >> + ARRAY_SIZE(layer_masks)); >> + >> + return allowed ? 0 : -EACCES; >> +} >> + >> +static u16 get_port(const struct sockaddr *const address) > > get_port() should return a __be16 type. This enables to avoid converting > port when checking a rule. > > make C=2 security/landlock/ must not print any warning. Got it. > > >> +{ >> + /* Gets port value in host byte order. */ >> + switch (address->sa_family) { >> + case AF_UNSPEC: >> + case AF_INET: { >> + const struct sockaddr_in *const sockaddr = >> + (struct sockaddr_in *)address; >> + return ntohs(sockaddr->sin_port); >> + } >> +#if IS_ENABLED(CONFIG_IPV6) >> + case AF_INET6: { >> + const struct sockaddr_in6 *const sockaddr_ip6 = >> + (struct sockaddr_in6 *)address; >> + return ntohs(sockaddr_ip6->sin6_port); >> + } >> +#endif >> + } >> + WARN_ON_ONCE(1); >> + return 0; >> +} >> + >> +static int hook_socket_bind(struct socket *sock, struct sockaddr *address, >> + int addrlen) >> +{ >> + const struct landlock_ruleset *const dom = >> + landlock_get_current_domain(); >> + >> + if (!dom) >> + return 0; >> + >> + /* Check if it's a TCP socket. */ >> + if (sock->type != SOCK_STREAM) >> + return 0; >> + >> + switch (address->sa_family) { >> + case AF_UNSPEC: >> + case AF_INET: >> +#if IS_ENABLED(CONFIG_IPV6) >> + case AF_INET6: >> +#endif >> + return check_socket_access(dom, get_port(address), >> + LANDLOCK_ACCESS_NET_BIND_TCP); >> + default: >> + return 0; > > You can remove this default case and move the return 0 at the end of the > function. > Ok. Will be refactored. > >> + } >> +} >> + >> +static int hook_socket_connect(struct socket *sock, struct sockaddr *address, >> + int addrlen) >> +{ >> + const struct landlock_ruleset *const dom = >> + landlock_get_current_domain(); >> + >> + if (!dom) >> + return 0; >> + >> + /* Check if it's a TCP socket. */ >> + if (sock->type != SOCK_STREAM) >> + return 0; >> + >> + /* Check if the hook is AF_INET* socket's action. */ >> + switch (address->sa_family) { >> + case AF_INET: >> +#if IS_ENABLED(CONFIG_IPV6) >> + case AF_INET6: >> +#endif >> + return check_socket_access(dom, get_port(address), >> + LANDLOCK_ACCESS_NET_CONNECT_TCP); >> + case AF_UNSPEC: { >> + u16 i; > > You can move "i" after the "dom" declaration to remove the extra braces. > Ok. Thanks. > >> + >> + /* >> + * If just in a layer a mask supports connect access, >> + * the socket_connect() hook with AF_UNSPEC family flag >> + * must be banned. This prevents from disconnecting already >> + * connected sockets. >> + */ >> + for (i = 0; i < dom->num_layers; i++) { >> + if (landlock_get_net_access_mask(dom, i) & >> + LANDLOCK_ACCESS_NET_CONNECT_TCP) >> + return -EACCES; > > I'm wondering if this is the right error code for this case. EPERM may > be more appropriate. Ok. Will be refactored. > > Thinking more about this case, I don't understand what is the rationale > to deny such action. What would be the consequence to always allow > connection with AF_UNSPEC (i.e. to disconnect a socket)? > I thought we have come to a conclusion about connect(...AF_UNSPEC..) behaviour in the patchset V3: https://lore.kernel.org/linux-security-module/19ad3a01-d76e-0e73-7833-99acd4afd97e@huawei.com/ > >> + } >> + } >> + } >> + return 0; >> +} >> + >> +static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { >> + LSM_HOOK_INIT(socket_bind, hook_socket_bind), >> + LSM_HOOK_INIT(socket_connect, hook_socket_connect), >> +}; >> + >> +__init void landlock_add_net_hooks(void) >> +{ >> + security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks), >> + LANDLOCK_NAME); >> +} >> diff --git a/security/landlock/net.h b/security/landlock/net.h >> new file mode 100644 >> index 000000000000..0da1d9dff5ab >> --- /dev/null >> +++ b/security/landlock/net.h >> @@ -0,0 +1,26 @@ >> +/* SPDX-License-Identifier: GPL-2.0-only */ >> +/* >> + * Landlock LSM - Network management and hooks >> + * >> + * Copyright © 2022 Huawei Tech. Co., Ltd. >> + */ >> + >> +#ifndef _SECURITY_LANDLOCK_NET_H >> +#define _SECURITY_LANDLOCK_NET_H >> + >> +#include "common.h" >> +#include "ruleset.h" >> +#include "setup.h" >> + >> +#if IS_ENABLED(CONFIG_INET) >> +__init void landlock_add_net_hooks(void); >> + >> +int landlock_append_net_rule(struct landlock_ruleset *const ruleset, >> + const u16 port, access_mask_t access_rights); >> +#else /* IS_ENABLED(CONFIG_INET) */ >> +static inline void landlock_add_net_hooks(void) >> +{ >> +} >> +#endif /* IS_ENABLED(CONFIG_INET) */ >> + >> +#endif /* _SECURITY_LANDLOCK_NET_H */ >> diff --git a/security/landlock/setup.c b/security/landlock/setup.c >> index 3f196d2ce4f9..7e4a598177b8 100644 >> --- a/security/landlock/setup.c >> +++ b/security/landlock/setup.c >> @@ -14,6 +14,7 @@ >> #include "fs.h" >> #include "ptrace.h" >> #include "setup.h" >> +#include "net.h" >> >> bool landlock_initialized __lsm_ro_after_init = false; >> >> @@ -29,6 +30,7 @@ static int __init landlock_init(void) >> landlock_add_cred_hooks(); >> landlock_add_ptrace_hooks(); >> landlock_add_fs_hooks(); >> + landlock_add_net_hooks(); >> landlock_initialized = true; >> pr_info("Up and running.\n"); >> return 0; >> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c >> index c5a6ad4e2fca..7853f32e8325 100644 >> --- a/security/landlock/syscalls.c >> +++ b/security/landlock/syscalls.c >> @@ -29,6 +29,7 @@ >> #include "cred.h" >> #include "fs.h" >> #include "limits.h" >> +#include "net.h" >> #include "ruleset.h" >> #include "setup.h" >> >> @@ -74,7 +75,8 @@ static void build_check_abi(void) >> { >> struct landlock_ruleset_attr ruleset_attr; >> struct landlock_path_beneath_attr path_beneath_attr; >> - size_t ruleset_size, path_beneath_size; >> + struct landlock_net_service_attr net_service_attr; >> + size_t ruleset_size, path_beneath_size, net_service_size; >> >> /* >> * For each user space ABI structures, first checks that there is no >> @@ -90,6 +92,11 @@ static void build_check_abi(void) >> path_beneath_size += sizeof(path_beneath_attr.parent_fd); >> BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size); >> BUILD_BUG_ON(sizeof(path_beneath_attr) != 12); >> + >> + net_service_size = sizeof(net_service_attr.allowed_access); >> + net_service_size += sizeof(net_service_attr.port); >> + BUILD_BUG_ON(sizeof(net_service_attr) != net_service_size); >> + BUILD_BUG_ON(sizeof(net_service_attr) != 10); >> } >> >> /* Ruleset handling */ >> @@ -322,13 +329,54 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, >> return err; >> } >> >> +static int add_rule_net_service(struct landlock_ruleset *ruleset, >> + const void __user *const rule_attr) >> +{ >> +#if IS_ENABLED(CONFIG_INET) >> + struct landlock_net_service_attr net_service_attr; >> + int res; >> + u32 mask; > > access_mask_t mask; Got it. Thanks. > > >> + >> + /* Copies raw user space buffer, only one type for now. */ >> + res = copy_from_user(&net_service_attr, rule_attr, >> + sizeof(net_service_attr)); >> + if (res) >> + return -EFAULT; >> + >> + /* >> + * Informs about useless rule: empty allowed_access (i.e. deny rules) >> + * are ignored by network actions. >> + */ >> + if (!net_service_attr.allowed_access) >> + return -ENOMSG; >> + >> + /* >> + * Checks that allowed_access matches the @ruleset constraints >> + * (ruleset->access_masks[0] is automatically upgraded to 64-bits). >> + */ >> + mask = landlock_get_net_access_mask(ruleset, 0); >> + if ((net_service_attr.allowed_access | mask) != mask) >> + return -EINVAL; >> + >> + /* Denies inserting a rule with port 0. */ >> + if (net_service_attr.port == 0) >> + return -EINVAL; >> + >> + /* Imports the new rule. */ >> + return landlock_append_net_rule(ruleset, net_service_attr.port, >> + net_service_attr.allowed_access); >> +#else /* IS_ENABLED(CONFIG_INET) */ >> + return -EAFNOSUPPORT; >> +#endif /* IS_ENABLED(CONFIG_INET) */ >> +} >> + >> /** >> * sys_landlock_add_rule - Add a new rule to a ruleset >> * >> * @ruleset_fd: File descriptor tied to the ruleset that should be extended >> * with the new rule. >> - * @rule_type: Identify the structure type pointed to by @rule_attr (only >> - * %LANDLOCK_RULE_PATH_BENEATH for now). >> + * @rule_type: Identify the structure type pointed to by @rule_attr: >> + * %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_SERVICE. >> * @rule_attr: Pointer to a rule (only of type &struct >> * landlock_path_beneath_attr for now). >> * @flags: Must be 0. >> @@ -339,6 +387,8 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, >> * Possible returned errors are: >> * >> * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time; >> + * - %EAFNOSUPPORT: @rule_type is LANDLOCK_RULE_NET_SERVICE but TCP/IP is not > > %LANDLOCK_RULE_NET_SERVICE Ok. > > >> + * supported by the running kernel; >> * - %EINVAL: @flags is not 0, or inconsistent access in the rule (i.e. >> * &landlock_path_beneath_attr.allowed_access is not a subset of the >> * ruleset handled accesses); >> @@ -373,6 +423,9 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd, >> case LANDLOCK_RULE_PATH_BENEATH: >> err = add_rule_path_beneath(ruleset, rule_attr); >> break; >> + case LANDLOCK_RULE_NET_SERVICE: >> + err = add_rule_net_service(ruleset, rule_attr); >> + break; >> default: >> err = -EINVAL; >> break; >> -- >> 2.25.1 >> > .
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