From: KP Singh <[email protected]>
The helper allows modification of certain bits on the linux_binprm
struct starting with the secureexec bit which can be updated using the
BPF_LSM_F_BPRM_SECUREEXEC flag.
secureexec can be set by the LSM for privilege gaining executions to set
the AT_SECURE auxv for glibc. When set, the dynamic linker disables the
use of certain environment variables (like LD_PRELOAD).
Signed-off-by: KP Singh <[email protected]>
---
include/uapi/linux/bpf.h | 18 ++++++++++++++++++
kernel/bpf/bpf_lsm.c | 27 +++++++++++++++++++++++++++
scripts/bpf_helpers_doc.py | 2 ++
tools/include/uapi/linux/bpf.h | 18 ++++++++++++++++++
4 files changed, 65 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 162999b12790..bfa79054d106 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3787,6 +3787,18 @@ union bpf_attr {
* *ARG_PTR_TO_BTF_ID* of type *task_struct*.
* Return
* Pointer to the current task.
+ *
+ * long bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags)
+ *
+ * Description
+ * Set or clear certain options on *bprm*:
+ *
+ * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit
+ * which sets the **AT_SECURE** auxv for glibc. The bit
+ * is cleared if the flag is not specified.
+ * Return
+ * **-EINVAL** if invalid *flags* are passed.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3948,6 +3960,7 @@ union bpf_attr {
FN(task_storage_get), \
FN(task_storage_delete), \
FN(get_current_task_btf), \
+ FN(lsm_set_bprm_opts), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4119,6 +4132,11 @@ enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_IP,
};
+/* Flags for LSM helpers */
+enum {
+ BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0),
+};
+
#define __bpf_md_ptr(type, name) \
union { \
type name; \
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 553107f4706a..cd85482228a0 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -7,6 +7,7 @@
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/btf.h>
+#include <linux/binfmts.h>
#include <linux/lsm_hooks.h>
#include <linux/bpf_lsm.h>
#include <linux/kallsyms.h>
@@ -51,6 +52,30 @@ int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
return 0;
}
+/* Mask for all the currently supported BPRM option flags */
+#define BPF_LSM_F_BRPM_OPTS_MASK BPF_LSM_F_BPRM_SECUREEXEC
+
+BPF_CALL_2(bpf_lsm_set_bprm_opts, struct linux_binprm *, bprm, u64, flags)
+{
+
+ if (flags & ~BPF_LSM_F_BRPM_OPTS_MASK)
+ return -EINVAL;
+
+ bprm->secureexec = (flags & BPF_LSM_F_BPRM_SECUREEXEC);
+ return 0;
+}
+
+BTF_ID_LIST_SINGLE(bpf_lsm_set_bprm_opts_btf_ids, struct, linux_binprm)
+
+const static struct bpf_func_proto bpf_lsm_set_bprm_opts_proto = {
+ .func = bpf_lsm_set_bprm_opts,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_btf_id = &bpf_lsm_set_bprm_opts_btf_ids[0],
+ .arg2_type = ARG_ANYTHING,
+};
+
static const struct bpf_func_proto *
bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -71,6 +96,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_task_storage_get_proto;
case BPF_FUNC_task_storage_delete:
return &bpf_task_storage_delete_proto;
+ case BPF_FUNC_lsm_set_bprm_opts:
+ return &bpf_lsm_set_bprm_opts_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 31484377b8b1..c5bc947a70ad 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -418,6 +418,7 @@ class PrinterHelpers(Printer):
'struct bpf_tcp_sock',
'struct bpf_tunnel_key',
'struct bpf_xfrm_state',
+ 'struct linux_binprm',
'struct pt_regs',
'struct sk_reuseport_md',
'struct sockaddr',
@@ -465,6 +466,7 @@ class PrinterHelpers(Printer):
'struct bpf_tcp_sock',
'struct bpf_tunnel_key',
'struct bpf_xfrm_state',
+ 'struct linux_binprm',
'struct pt_regs',
'struct sk_reuseport_md',
'struct sockaddr',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 162999b12790..bfa79054d106 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3787,6 +3787,18 @@ union bpf_attr {
* *ARG_PTR_TO_BTF_ID* of type *task_struct*.
* Return
* Pointer to the current task.
+ *
+ * long bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags)
+ *
+ * Description
+ * Set or clear certain options on *bprm*:
+ *
+ * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit
+ * which sets the **AT_SECURE** auxv for glibc. The bit
+ * is cleared if the flag is not specified.
+ * Return
+ * **-EINVAL** if invalid *flags* are passed.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3948,6 +3960,7 @@ union bpf_attr {
FN(task_storage_get), \
FN(task_storage_delete), \
FN(get_current_task_btf), \
+ FN(lsm_set_bprm_opts), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4119,6 +4132,11 @@ enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_IP,
};
+/* Flags for LSM helpers */
+enum {
+ BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0),
+};
+
#define __bpf_md_ptr(type, name) \
union { \
type name; \
--
2.29.2.299.gdc1121823c-goog
On Tue, Nov 17, 2020 at 02:13:06AM +0000, KP Singh wrote:
> From: KP Singh <[email protected]>
>
> The helper allows modification of certain bits on the linux_binprm
> struct starting with the secureexec bit which can be updated using the
> BPF_LSM_F_BPRM_SECUREEXEC flag.
>
> secureexec can be set by the LSM for privilege gaining executions to set
> the AT_SECURE auxv for glibc. When set, the dynamic linker disables the
> use of certain environment variables (like LD_PRELOAD).
>
> Signed-off-by: KP Singh <[email protected]>
Acked-by: Martin KaFai Lau <[email protected]>
On 11/17/20 3:13 AM, KP Singh wrote:
> From: KP Singh <[email protected]>
>
> The helper allows modification of certain bits on the linux_binprm
> struct starting with the secureexec bit which can be updated using the
> BPF_LSM_F_BPRM_SECUREEXEC flag.
>
> secureexec can be set by the LSM for privilege gaining executions to set
> the AT_SECURE auxv for glibc. When set, the dynamic linker disables the
> use of certain environment variables (like LD_PRELOAD).
>
> Signed-off-by: KP Singh <[email protected]>
> ---
> include/uapi/linux/bpf.h | 18 ++++++++++++++++++
> kernel/bpf/bpf_lsm.c | 27 +++++++++++++++++++++++++++
> scripts/bpf_helpers_doc.py | 2 ++
> tools/include/uapi/linux/bpf.h | 18 ++++++++++++++++++
> 4 files changed, 65 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 162999b12790..bfa79054d106 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3787,6 +3787,18 @@ union bpf_attr {
> * *ARG_PTR_TO_BTF_ID* of type *task_struct*.
> * Return
> * Pointer to the current task.
> + *
> + * long bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags)
> + *
small nit: should have no extra newline (same for the tools/ copy)
> + * Description
> + * Set or clear certain options on *bprm*:
> + *
> + * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit
> + * which sets the **AT_SECURE** auxv for glibc. The bit
> + * is cleared if the flag is not specified.
> + * Return
> + * **-EINVAL** if invalid *flags* are passed.
> + *
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3948,6 +3960,7 @@ union bpf_attr {
> FN(task_storage_get), \
> FN(task_storage_delete), \
> FN(get_current_task_btf), \
> + FN(lsm_set_bprm_opts), \
> /* */
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> @@ -4119,6 +4132,11 @@ enum bpf_lwt_encap_mode {
> BPF_LWT_ENCAP_IP,
> };
>
> +/* Flags for LSM helpers */
> +enum {
> + BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0),
> +};
> +
> #define __bpf_md_ptr(type, name) \
> union { \
> type name; \
> diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> index 553107f4706a..cd85482228a0 100644
> --- a/kernel/bpf/bpf_lsm.c
> +++ b/kernel/bpf/bpf_lsm.c
> @@ -7,6 +7,7 @@
> #include <linux/filter.h>
> #include <linux/bpf.h>
> #include <linux/btf.h>
> +#include <linux/binfmts.h>
> #include <linux/lsm_hooks.h>
> #include <linux/bpf_lsm.h>
> #include <linux/kallsyms.h>
> @@ -51,6 +52,30 @@ int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
> return 0;
> }
>
> +/* Mask for all the currently supported BPRM option flags */
> +#define BPF_LSM_F_BRPM_OPTS_MASK BPF_LSM_F_BPRM_SECUREEXEC
> +
> +BPF_CALL_2(bpf_lsm_set_bprm_opts, struct linux_binprm *, bprm, u64, flags)
> +{
> +
ditto
Would have fixed up these things on the fly while applying, but one small item
I wanted to bring up here given uapi which will then freeze: it would be cleaner
to call the helper just bpf_bprm_opts_set() or so given it's implied that we
attach to lsm here and we don't use _lsm in the naming for the others either.
Similarly, I'd drop the _LSM from the flag/mask.
> + if (flags & ~BPF_LSM_F_BRPM_OPTS_MASK)
> + return -EINVAL;
> +
> + bprm->secureexec = (flags & BPF_LSM_F_BPRM_SECUREEXEC);
> + return 0;
> +}
> +
> +BTF_ID_LIST_SINGLE(bpf_lsm_set_bprm_opts_btf_ids, struct, linux_binprm)
> +
> +const static struct bpf_func_proto bpf_lsm_set_bprm_opts_proto = {
> + .func = bpf_lsm_set_bprm_opts,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_BTF_ID,
> + .arg1_btf_id = &bpf_lsm_set_bprm_opts_btf_ids[0],
> + .arg2_type = ARG_ANYTHING,
> +};
> +
> static const struct bpf_func_proto *
> bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> {
> @@ -71,6 +96,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> return &bpf_task_storage_get_proto;
> case BPF_FUNC_task_storage_delete:
> return &bpf_task_storage_delete_proto;
> + case BPF_FUNC_lsm_set_bprm_opts:
> + return &bpf_lsm_set_bprm_opts_proto;
> default:
> return tracing_prog_func_proto(func_id, prog);
> }
On Tue, Nov 17, 2020 at 11:41 PM Daniel Borkmann <[email protected]> wrote:
>
> On 11/17/20 3:13 AM, KP Singh wrote:
> > From: KP Singh <[email protected]>
> >
> > The helper allows modification of certain bits on the linux_binprm
> > struct starting with the secureexec bit which can be updated using the
> > BPF_LSM_F_BPRM_SECUREEXEC flag.
> >
> > secureexec can be set by the LSM for privilege gaining executions to set
> > the AT_SECURE auxv for glibc. When set, the dynamic linker disables the
> > use of certain environment variables (like LD_PRELOAD).
> >
> > Signed-off-by: KP Singh <[email protected]>
> > ---
> > include/uapi/linux/bpf.h | 18 ++++++++++++++++++
> > kernel/bpf/bpf_lsm.c | 27 +++++++++++++++++++++++++++
> > scripts/bpf_helpers_doc.py | 2 ++
> > tools/include/uapi/linux/bpf.h | 18 ++++++++++++++++++
> > 4 files changed, 65 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 162999b12790..bfa79054d106 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -3787,6 +3787,18 @@ union bpf_attr {
> > * *ARG_PTR_TO_BTF_ID* of type *task_struct*.
> > * Return
> > * Pointer to the current task.
> > + *
> > + * long bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags)
> > + *
>
> small nit: should have no extra newline (same for the tools/ copy)
>
> > + * Description
> > + * Set or clear certain options on *bprm*:
> > + *
> > + * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit
> > + * which sets the **AT_SECURE** auxv for glibc. The bit
> > + * is cleared if the flag is not specified.
> > + * Return
> > + * **-EINVAL** if invalid *flags* are passed.
> > + *
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -3948,6 +3960,7 @@ union bpf_attr {
> > FN(task_storage_get), \
> > FN(task_storage_delete), \
> > FN(get_current_task_btf), \
> > + FN(lsm_set_bprm_opts), \
> > /* */
> >
> > /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > @@ -4119,6 +4132,11 @@ enum bpf_lwt_encap_mode {
> > BPF_LWT_ENCAP_IP,
> > };
> >
> > +/* Flags for LSM helpers */
> > +enum {
> > + BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0),
> > +};
> > +
> > #define __bpf_md_ptr(type, name) \
> > union { \
> > type name; \
> > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> > index 553107f4706a..cd85482228a0 100644
> > --- a/kernel/bpf/bpf_lsm.c
> > +++ b/kernel/bpf/bpf_lsm.c
> > @@ -7,6 +7,7 @@
> > #include <linux/filter.h>
> > #include <linux/bpf.h>
> > #include <linux/btf.h>
> > +#include <linux/binfmts.h>
> > #include <linux/lsm_hooks.h>
> > #include <linux/bpf_lsm.h>
> > #include <linux/kallsyms.h>
> > @@ -51,6 +52,30 @@ int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
> > return 0;
> > }
> >
> > +/* Mask for all the currently supported BPRM option flags */
> > +#define BPF_LSM_F_BRPM_OPTS_MASK BPF_LSM_F_BPRM_SECUREEXEC
> > +
> > +BPF_CALL_2(bpf_lsm_set_bprm_opts, struct linux_binprm *, bprm, u64, flags)
> > +{
> > +
>
> ditto
>
> Would have fixed up these things on the fly while applying, but one small item
> I wanted to bring up here given uapi which will then freeze: it would be cleaner
> to call the helper just bpf_bprm_opts_set() or so given it's implied that we
> attach to lsm here and we don't use _lsm in the naming for the others either.
> Similarly, I'd drop the _LSM from the flag/mask.
>
Thanks Daniel, this makes sense and is more future proof, I respun this and
sent out another version with some minor fixes and the rename. Also added
Martin's acks.
- KP