On 8/9/22 3:46 PM, Roberto Sassu wrote:
[...]
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@xxxxxxxxxx>
---
kernel/trace/bpf_trace.c | 56 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 33ca4cfe6e26..79ba8c96735a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -21,6 +21,7 @@
#include <linux/bsearch.h>
#include <linux/sort.h>
#include <linux/key.h>
+#include <linux/verification.h>
#include <net/bpf_sk_storage.h>
@@ -1290,6 +1291,47 @@ noinline __weak 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.
+ */
+noinline __weak int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
nit: see comment on prev patch for noinline and __weak
+ struct bpf_dynptr_kern *sig_ptr,
+ struct bpf_key *trusted_keyring)
+{
+ int ret;
+
+ if (trusted_keyring->valid_ptr) {
+ /*
+ * Do the permission check deferred in bpf_lookup_user_key().
+ *
+ * A call to key_task_permission() here would be redundant, as
+ * it is already done by keyring_search() called by
+ * find_asymmetric_key().
+ */
In this patch and previous one, you describe that calling key_validate() is
deferred, but you should also provide the actual rationale for readers on
"why" we need to do it.
+ 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),
+ trusted_keyring->key,
+ VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
+ NULL);
+}
+#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
+
__diag_pop();
BTF_SET8_START(key_kfunc_set)
@@ -1303,11 +1345,25 @@ static const struct btf_kfunc_id_set bpf_key_kfunc_set = {
.owner = THIS_MODULE,
.set = &key_kfunc_set,
};
