On Tue, 2022-09-06 at 04:57 +0200, Kumar Kartikeya Dwivedi wrote:
On Mon, 5 Sept 2022 at 16:35, Roberto Sassu roberto.sassu@huaweicloud.com wrote:
From: Roberto Sassu roberto.sassu@huawei.com
Add the bpf_verify_pkcs7_signature() kfunc, to give eBPF security modules the ability to check the validity of a signature against supplied data, by using user-provided or system-provided keys as trust anchor.
The new kfunc makes it possible to enforce mandatory policies, as eBPF programs might be allowed to make security decisions only based on data sources the system administrator approves.
The caller should provide the data to be verified and the signature as eBPF dynamic pointers (to minimize the number of parameters) and a bpf_key structure containing a reference to the keyring with keys trusted for signature verification, obtained from bpf_lookup_user_key() or bpf_lookup_system_key().
For bpf_key structures obtained from the former lookup function, bpf_verify_pkcs7_signature() completes the permission check deferred by that function by calling key_validate(). key_task_permission() is already called by the PKCS#7 code.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com Acked-by: KP Singh kpsingh@kernel.org
kernel/trace/bpf_trace.c | 45 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 7a7023704ac2..8e2c026b0a58 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1294,12 +1294,57 @@ void bpf_key_put(struct bpf_key *bkey) kfree(bkey); }
+#ifdef CONFIG_SYSTEM_DATA_VERIFICATION +/**
- bpf_verify_pkcs7_signature - verify a PKCS#7 signature
- @data_ptr: data to verify
- @sig_ptr: signature of the data
- @trusted_keyring: keyring with keys trusted for signature
verification
- Verify the PKCS#7 signature *sig_ptr* against the supplied
*data_ptr*
- with keys in a keyring referenced by *trusted_keyring*.
- Return: 0 on success, a negative value on error.
- */
+int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
struct bpf_dynptr_kern *sig_ptr,struct bpf_key *trusted_keyring)+{
int ret;if (trusted_keyring->has_ref) {/** Do the permission check deferred inbpf_lookup_user_key().
* See bpf_lookup_user_key() for more details.** A call to key_task_permission() here would beredundant, as
* it is already done by keyring_search() called by* find_asymmetric_key().*/ret = key_validate(trusted_keyring->key);if (ret < 0)return ret;}return verify_pkcs7_signature(data_ptr->data,bpf_dynptr_get_size(data_ptr),
sig_ptr->data,bpf_dynptr_get_size(sig_ptr),MIssing check for data_ptr->data == NULL before making this call? Same for sig_ptr.
Patch 3 requires the dynptrs to be initialized. Isn't enough?
Thanks
Roberto