bpf-lsm: Introduce new helper bpf_ima_file_hash()

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

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e9978a9..99fab54 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -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

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 9e4ecc9..e8d27af 100644 (file)
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -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);
        }

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index e9978a9..99fab54 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -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