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linux-stable/kernel/bpf/token.c

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bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
#include <linux/bpf.h>
#include <linux/vmalloc.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/user_namespace.h>
bpf,lsm: Add BPF token LSM hooks Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to allocate LSM security blob (we add `void *security` field to struct bpf_token for that), but also control who can instantiate BPF token. This follows existing pattern for BPF map and BPF prog. Also add security_bpf_token_allow_cmd() and security_bpf_token_capable() LSM hooks that allow LSM implementation to control and negate (if necessary) BPF token's delegation of a specific bpf_cmd and capability, respectively. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/bpf/20240124022127.2379740-12-andrii@kernel.org
2024-01-24 02:21:08 +00:00
#include <linux/security.h>
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
static bool bpf_ns_capable(struct user_namespace *ns, int cap)
{
return ns_capable(ns, cap) || (cap != CAP_SYS_ADMIN && ns_capable(ns, CAP_SYS_ADMIN));
}
bool bpf_token_capable(const struct bpf_token *token, int cap)
{
struct user_namespace *userns;
/* BPF token allows ns_capable() level of capabilities */
userns = token ? token->userns : &init_user_ns;
if (!bpf_ns_capable(userns, cap))
return false;
bpf,lsm: Add BPF token LSM hooks Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to allocate LSM security blob (we add `void *security` field to struct bpf_token for that), but also control who can instantiate BPF token. This follows existing pattern for BPF map and BPF prog. Also add security_bpf_token_allow_cmd() and security_bpf_token_capable() LSM hooks that allow LSM implementation to control and negate (if necessary) BPF token's delegation of a specific bpf_cmd and capability, respectively. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/bpf/20240124022127.2379740-12-andrii@kernel.org
2024-01-24 02:21:08 +00:00
if (token && security_bpf_token_capable(token, cap) < 0)
return false;
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
return true;
}
void bpf_token_inc(struct bpf_token *token)
{
atomic64_inc(&token->refcnt);
}
static void bpf_token_free(struct bpf_token *token)
{
bpf,lsm: Add BPF token LSM hooks Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to allocate LSM security blob (we add `void *security` field to struct bpf_token for that), but also control who can instantiate BPF token. This follows existing pattern for BPF map and BPF prog. Also add security_bpf_token_allow_cmd() and security_bpf_token_capable() LSM hooks that allow LSM implementation to control and negate (if necessary) BPF token's delegation of a specific bpf_cmd and capability, respectively. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/bpf/20240124022127.2379740-12-andrii@kernel.org
2024-01-24 02:21:08 +00:00
security_bpf_token_free(token);
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
put_user_ns(token->userns);
kfree(token);
}
static void bpf_token_put_deferred(struct work_struct *work)
{
struct bpf_token *token = container_of(work, struct bpf_token, work);
bpf_token_free(token);
}
void bpf_token_put(struct bpf_token *token)
{
if (!token)
return;
if (!atomic64_dec_and_test(&token->refcnt))
return;
INIT_WORK(&token->work, bpf_token_put_deferred);
schedule_work(&token->work);
}
static int bpf_token_release(struct inode *inode, struct file *filp)
{
struct bpf_token *token = filp->private_data;
bpf_token_put(token);
return 0;
}
static void bpf_token_show_fdinfo(struct seq_file *m, struct file *filp)
{
struct bpf_token *token = filp->private_data;
u64 mask;
BUILD_BUG_ON(__MAX_BPF_CMD >= 64);
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
mask = BIT_ULL(__MAX_BPF_CMD) - 1;
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
if ((token->allowed_cmds & mask) == mask)
seq_printf(m, "allowed_cmds:\tany\n");
else
seq_printf(m, "allowed_cmds:\t0x%llx\n", token->allowed_cmds);
bpf: Add BPF token support to BPF_MAP_CREATE command Allow providing token_fd for BPF_MAP_CREATE command to allow controlled BPF map creation from unprivileged process through delegated BPF token. New BPF_F_TOKEN_FD flag is added to specify together with BPF token FD for BPF_MAP_CREATE command. Wire through a set of allowed BPF map types to BPF token, derived from BPF FS at BPF token creation time. This, in combination with allowed_cmds allows to create a narrowly-focused BPF token (controlled by privileged agent) with a restrictive set of BPF maps that application can attempt to create. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-5-andrii@kernel.org
2024-01-24 02:21:01 +00:00
BUILD_BUG_ON(__MAX_BPF_MAP_TYPE >= 64);
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
mask = BIT_ULL(__MAX_BPF_MAP_TYPE) - 1;
bpf: Add BPF token support to BPF_MAP_CREATE command Allow providing token_fd for BPF_MAP_CREATE command to allow controlled BPF map creation from unprivileged process through delegated BPF token. New BPF_F_TOKEN_FD flag is added to specify together with BPF token FD for BPF_MAP_CREATE command. Wire through a set of allowed BPF map types to BPF token, derived from BPF FS at BPF token creation time. This, in combination with allowed_cmds allows to create a narrowly-focused BPF token (controlled by privileged agent) with a restrictive set of BPF maps that application can attempt to create. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-5-andrii@kernel.org
2024-01-24 02:21:01 +00:00
if ((token->allowed_maps & mask) == mask)
seq_printf(m, "allowed_maps:\tany\n");
else
seq_printf(m, "allowed_maps:\t0x%llx\n", token->allowed_maps);
bpf: Add BPF token support to BPF_PROG_LOAD command Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag should be set in prog_flags field when providing prog_token_fd. Wire through a set of allowed BPF program types and attach types, derived from BPF FS at BPF token creation time. Then make sure we perform bpf_token_capable() checks everywhere where it's relevant. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org
2024-01-24 02:21:03 +00:00
BUILD_BUG_ON(__MAX_BPF_PROG_TYPE >= 64);
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
mask = BIT_ULL(__MAX_BPF_PROG_TYPE) - 1;
bpf: Add BPF token support to BPF_PROG_LOAD command Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag should be set in prog_flags field when providing prog_token_fd. Wire through a set of allowed BPF program types and attach types, derived from BPF FS at BPF token creation time. Then make sure we perform bpf_token_capable() checks everywhere where it's relevant. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org
2024-01-24 02:21:03 +00:00
if ((token->allowed_progs & mask) == mask)
seq_printf(m, "allowed_progs:\tany\n");
else
seq_printf(m, "allowed_progs:\t0x%llx\n", token->allowed_progs);
BUILD_BUG_ON(__MAX_BPF_ATTACH_TYPE >= 64);
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
mask = BIT_ULL(__MAX_BPF_ATTACH_TYPE) - 1;
bpf: Add BPF token support to BPF_PROG_LOAD command Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag should be set in prog_flags field when providing prog_token_fd. Wire through a set of allowed BPF program types and attach types, derived from BPF FS at BPF token creation time. Then make sure we perform bpf_token_capable() checks everywhere where it's relevant. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org
2024-01-24 02:21:03 +00:00
if ((token->allowed_attachs & mask) == mask)
seq_printf(m, "allowed_attachs:\tany\n");
else
seq_printf(m, "allowed_attachs:\t0x%llx\n", token->allowed_attachs);
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
}
#define BPF_TOKEN_INODE_NAME "bpf-token"
static const struct inode_operations bpf_token_iops = { };
static const struct file_operations bpf_token_fops = {
.release = bpf_token_release,
.show_fdinfo = bpf_token_show_fdinfo,
};
int bpf_token_create(union bpf_attr *attr)
{
struct bpf_mount_opts *mnt_opts;
struct bpf_token *token = NULL;
struct user_namespace *userns;
struct inode *inode;
struct file *file;
struct path path;
struct fd f;
umode_t mode;
int err, fd;
f = fdget(attr->token_create.bpffs_fd);
if (!f.file)
return -EBADF;
path = f.file->f_path;
path_get(&path);
fdput(f);
if (path.dentry != path.mnt->mnt_sb->s_root) {
err = -EINVAL;
goto out_path;
}
if (path.mnt->mnt_sb->s_op != &bpf_super_ops) {
err = -EINVAL;
goto out_path;
}
err = path_permission(&path, MAY_ACCESS);
if (err)
goto out_path;
userns = path.dentry->d_sb->s_user_ns;
/*
* Enforce that creators of BPF tokens are in the same user
* namespace as the BPF FS instance. This makes reasoning about
* permissions a lot easier and we can always relax this later.
*/
if (current_user_ns() != userns) {
err = -EPERM;
goto out_path;
}
if (!ns_capable(userns, CAP_BPF)) {
err = -EPERM;
goto out_path;
}
/* Creating BPF token in init_user_ns doesn't make much sense. */
if (current_user_ns() == &init_user_ns) {
err = -EOPNOTSUPP;
goto out_path;
}
bpf: Fail BPF_TOKEN_CREATE if no delegation option was set on BPF FS It's quite confusing in practice when it's possible to successfully create a BPF token from BPF FS that didn't have any of delegate_xxx mount options set up. While it's not wrong, it's actually more meaningful to reject BPF_TOKEN_CREATE with specific error code (-ENOENT) to let user-space know that no token delegation is setup up. So, instead of creating empty BPF token that will be always ignored because it doesn't have any of the allow_xxx bits set, reject it with -ENOENT. If we ever need empty BPF token to be possible, we can support that with extra flag passed into BPF_TOKEN_CREATE. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20240124022127.2379740-19-andrii@kernel.org
2024-01-24 02:21:15 +00:00
mnt_opts = path.dentry->d_sb->s_fs_info;
if (mnt_opts->delegate_cmds == 0 &&
mnt_opts->delegate_maps == 0 &&
mnt_opts->delegate_progs == 0 &&
mnt_opts->delegate_attachs == 0) {
err = -ENOENT; /* no BPF token delegation is set up */
goto out_path;
}
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
inode = bpf_get_inode(path.mnt->mnt_sb, NULL, mode);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out_path;
}
inode->i_op = &bpf_token_iops;
inode->i_fop = &bpf_token_fops;
clear_nlink(inode); /* make sure it is unlinked */
file = alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, O_RDWR, &bpf_token_fops);
if (IS_ERR(file)) {
iput(inode);
err = PTR_ERR(file);
goto out_path;
}
token = kzalloc(sizeof(*token), GFP_USER);
if (!token) {
err = -ENOMEM;
goto out_file;
}
atomic64_set(&token->refcnt, 1);
/* remember bpffs owning userns for future ns_capable() checks */
token->userns = get_user_ns(userns);
token->allowed_cmds = mnt_opts->delegate_cmds;
bpf: Add BPF token support to BPF_MAP_CREATE command Allow providing token_fd for BPF_MAP_CREATE command to allow controlled BPF map creation from unprivileged process through delegated BPF token. New BPF_F_TOKEN_FD flag is added to specify together with BPF token FD for BPF_MAP_CREATE command. Wire through a set of allowed BPF map types to BPF token, derived from BPF FS at BPF token creation time. This, in combination with allowed_cmds allows to create a narrowly-focused BPF token (controlled by privileged agent) with a restrictive set of BPF maps that application can attempt to create. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-5-andrii@kernel.org
2024-01-24 02:21:01 +00:00
token->allowed_maps = mnt_opts->delegate_maps;
bpf: Add BPF token support to BPF_PROG_LOAD command Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag should be set in prog_flags field when providing prog_token_fd. Wire through a set of allowed BPF program types and attach types, derived from BPF FS at BPF token creation time. Then make sure we perform bpf_token_capable() checks everywhere where it's relevant. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org
2024-01-24 02:21:03 +00:00
token->allowed_progs = mnt_opts->delegate_progs;
token->allowed_attachs = mnt_opts->delegate_attachs;
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
bpf,lsm: Add BPF token LSM hooks Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to allocate LSM security blob (we add `void *security` field to struct bpf_token for that), but also control who can instantiate BPF token. This follows existing pattern for BPF map and BPF prog. Also add security_bpf_token_allow_cmd() and security_bpf_token_capable() LSM hooks that allow LSM implementation to control and negate (if necessary) BPF token's delegation of a specific bpf_cmd and capability, respectively. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/bpf/20240124022127.2379740-12-andrii@kernel.org
2024-01-24 02:21:08 +00:00
err = security_bpf_token_create(token, attr, &path);
if (err)
goto out_token;
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
fd = get_unused_fd_flags(O_CLOEXEC);
if (fd < 0) {
err = fd;
goto out_token;
}
file->private_data = token;
fd_install(fd, file);
path_put(&path);
return fd;
out_token:
bpf_token_free(token);
out_file:
fput(file);
out_path:
path_put(&path);
return err;
}
struct bpf_token *bpf_token_get_from_fd(u32 ufd)
{
struct fd f = fdget(ufd);
struct bpf_token *token;
if (!f.file)
return ERR_PTR(-EBADF);
if (f.file->f_op != &bpf_token_fops) {
fdput(f);
return ERR_PTR(-EINVAL);
}
token = f.file->private_data;
bpf_token_inc(token);
fdput(f);
return token;
}
bool bpf_token_allow_cmd(const struct bpf_token *token, enum bpf_cmd cmd)
{
if (!token)
return false;
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
if (!(token->allowed_cmds & BIT_ULL(cmd)))
bpf,lsm: Add BPF token LSM hooks Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to allocate LSM security blob (we add `void *security` field to struct bpf_token for that), but also control who can instantiate BPF token. This follows existing pattern for BPF map and BPF prog. Also add security_bpf_token_allow_cmd() and security_bpf_token_capable() LSM hooks that allow LSM implementation to control and negate (if necessary) BPF token's delegation of a specific bpf_cmd and capability, respectively. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/bpf/20240124022127.2379740-12-andrii@kernel.org
2024-01-24 02:21:08 +00:00
return false;
return security_bpf_token_cmd(token, cmd) == 0;
bpf: Introduce BPF token object Add new kind of BPF kernel object, BPF token. BPF token is meant to allow delegating privileged BPF functionality, like loading a BPF program or creating a BPF map, from privileged process to a *trusted* unprivileged process, all while having a good amount of control over which privileged operations could be performed using provided BPF token. This is achieved through mounting BPF FS instance with extra delegation mount options, which determine what operations are delegatable, and also constraining it to the owning user namespace (as mentioned in the previous patch). BPF token itself is just a derivative from BPF FS and can be created through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF FS FD, which can be attained through open() API by opening BPF FS mount point. Currently, BPF token "inherits" delegated command, map types, prog type, and attach type bit sets from BPF FS as is. In the future, having an BPF token as a separate object with its own FD, we can allow to further restrict BPF token's allowable set of things either at the creation time or after the fact, allowing the process to guard itself further from unintentionally trying to load undesired kind of BPF programs. But for now we keep things simple and just copy bit sets as is. When BPF token is created from BPF FS mount, we take reference to the BPF super block's owning user namespace, and then use that namespace for checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN} capabilities that are normally only checked against init userns (using capable()), but now we check them using ns_capable() instead (if BPF token is provided). See bpf_token_capable() for details. Such setup means that BPF token in itself is not sufficient to grant BPF functionality. User namespaced process has to *also* have necessary combination of capabilities inside that user namespace. So while previously CAP_BPF was useless when granted within user namespace, now it gains a meaning and allows container managers and sys admins to have a flexible control over which processes can and need to use BPF functionality within the user namespace (i.e., container in practice). And BPF FS delegation mount options and derived BPF tokens serve as a per-container "flag" to grant overall ability to use bpf() (plus further restrict on which parts of bpf() syscalls are treated as namespaced). Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF) within the BPF FS owning user namespace, rounding up the ns_capable() story of BPF token. Also creating BPF token in init user namespace is currently not supported, given BPF token doesn't have any effect in init user namespace anyways. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-4-andrii@kernel.org
2024-01-24 02:21:00 +00:00
}
bpf: Add BPF token support to BPF_MAP_CREATE command Allow providing token_fd for BPF_MAP_CREATE command to allow controlled BPF map creation from unprivileged process through delegated BPF token. New BPF_F_TOKEN_FD flag is added to specify together with BPF token FD for BPF_MAP_CREATE command. Wire through a set of allowed BPF map types to BPF token, derived from BPF FS at BPF token creation time. This, in combination with allowed_cmds allows to create a narrowly-focused BPF token (controlled by privileged agent) with a restrictive set of BPF maps that application can attempt to create. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-5-andrii@kernel.org
2024-01-24 02:21:01 +00:00
bool bpf_token_allow_map_type(const struct bpf_token *token, enum bpf_map_type type)
{
if (!token || type >= __MAX_BPF_MAP_TYPE)
return false;
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
return token->allowed_maps & BIT_ULL(type);
bpf: Add BPF token support to BPF_MAP_CREATE command Allow providing token_fd for BPF_MAP_CREATE command to allow controlled BPF map creation from unprivileged process through delegated BPF token. New BPF_F_TOKEN_FD flag is added to specify together with BPF token FD for BPF_MAP_CREATE command. Wire through a set of allowed BPF map types to BPF token, derived from BPF FS at BPF token creation time. This, in combination with allowed_cmds allows to create a narrowly-focused BPF token (controlled by privileged agent) with a restrictive set of BPF maps that application can attempt to create. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-5-andrii@kernel.org
2024-01-24 02:21:01 +00:00
}
bpf: Add BPF token support to BPF_PROG_LOAD command Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag should be set in prog_flags field when providing prog_token_fd. Wire through a set of allowed BPF program types and attach types, derived from BPF FS at BPF token creation time. Then make sure we perform bpf_token_capable() checks everywhere where it's relevant. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org
2024-01-24 02:21:03 +00:00
bool bpf_token_allow_prog_type(const struct bpf_token *token,
enum bpf_prog_type prog_type,
enum bpf_attach_type attach_type)
{
if (!token || prog_type >= __MAX_BPF_PROG_TYPE || attach_type >= __MAX_BPF_ATTACH_TYPE)
return false;
bpf,token: Use BIT_ULL() to convert the bit mask Replace the '(1ULL << *)' with the macro BIT_ULL(nr). Signed-off-by: Haiyue Wang <haiyue.wang@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240127134901.3698613-1-haiyue.wang@intel.com
2024-01-27 13:48:56 +00:00
return (token->allowed_progs & BIT_ULL(prog_type)) &&
(token->allowed_attachs & BIT_ULL(attach_type));
bpf: Add BPF token support to BPF_PROG_LOAD command Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag should be set in prog_flags field when providing prog_token_fd. Wire through a set of allowed BPF program types and attach types, derived from BPF FS at BPF token creation time. Then make sure we perform bpf_token_capable() checks everywhere where it's relevant. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org
2024-01-24 02:21:03 +00:00
}