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bpf-lsm: Introduce new helper bpf_ima_file_hash()

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ima_file_hash() has been modified to calculate the measurement of a file on
demand, if it has not been already performed by IMA or the measurement is
not fresh. For compatibility reasons, ima_inode_hash() remains unchanged.

Keep the same approach in eBPF and introduce the new helper
bpf_ima_file_hash() to take advantage of the modified behavior of
ima_file_hash().

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220302111404.193900-4-roberto.sassu@huawei.com
This commit is contained in:
Roberto Sassu 2022-03-02 12:13:58 +01:00 committed by Alexei Starovoitov
parent 280fe8367b
commit 174b16946e
3 changed files with 42 additions and 0 deletions
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11
include/uapi/linux/bpf.h
View File

@ -5119,6 +5119,16 @@ union bpf_attr {
* 0 on success.
* **-EINVAL** for invalid input
* **-EOPNOTSUPP** for unsupported protocol
*
* long bpf_ima_file_hash(struct file *file, void *dst, u32 size)
* Description
* Returns a calculated IMA hash of the *file*.
* If the hash is larger than *size*, then only *size*
* bytes will be copied to *dst*
* Return
* The **hash_algo** is returned on success,
* **-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
* invalid arguments are passed.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -5314,6 +5324,7 @@ union bpf_attr {
FN(xdp_store_bytes), \
FN(copy_from_user_task), \
FN(skb_set_tstamp), \
FN(ima_file_hash), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper

20
kernel/bpf/bpf_lsm.c
View File

@ -99,6 +99,24 @@ static const struct bpf_func_proto bpf_ima_inode_hash_proto = {
.allowed = bpf_ima_inode_hash_allowed,
};
BPF_CALL_3(bpf_ima_file_hash, struct file *, file, void *, dst, u32, size)
{
return ima_file_hash(file, dst, size);
}
BTF_ID_LIST_SINGLE(bpf_ima_file_hash_btf_ids, struct, file)
static const struct bpf_func_proto bpf_ima_file_hash_proto = {
.func = bpf_ima_file_hash,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_BTF_ID,
.arg1_btf_id = &bpf_ima_file_hash_btf_ids[0],
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE,
.allowed = bpf_ima_inode_hash_allowed,
};
static const struct bpf_func_proto *
bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@ -121,6 +139,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_bprm_opts_set_proto;
case BPF_FUNC_ima_inode_hash:
return prog->aux->sleepable ? &bpf_ima_inode_hash_proto : NULL;
case BPF_FUNC_ima_file_hash:
return prog->aux->sleepable ? &bpf_ima_file_hash_proto : NULL;
default:
return tracing_prog_func_proto(func_id, prog);
}

11
tools/include/uapi/linux/bpf.h
View File

@ -5119,6 +5119,16 @@ union bpf_attr {
* 0 on success.
* **-EINVAL** for invalid input
* **-EOPNOTSUPP** for unsupported protocol
*
* long bpf_ima_file_hash(struct file *file, void *dst, u32 size)
* Description
* Returns a calculated IMA hash of the *file*.
* If the hash is larger than *size*, then only *size*
* bytes will be copied to *dst*
* Return
* The **hash_algo** is returned on success,
* **-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
* invalid arguments are passed.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -5314,6 +5324,7 @@ union bpf_attr {
FN(xdp_store_bytes), \
FN(copy_from_user_task), \
FN(skb_set_tstamp), \
FN(ima_file_hash), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper