[RFC][PATCH 09/10] bpf: Introduce bpf_verify_uasym_signature() kfunc

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu at huawei.com>

Introduce the bpf_verify_uasym_signature() kfunc, to verify user asymmetric
key signatures. The parameters and usage are the same as for
bpf_verify_pkcs7_signature().

Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
---
 kernel/trace/bpf_trace.c | 68 +++++++++++++++++++++++++++++++---------
 1 file changed, 54 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 5f2dcabad20..476b6d526de 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1281,7 +1281,7 @@ __bpf_kfunc struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags)
  * The key pointer is marked as invalid, to prevent bpf_key_put() from
  * attempting to decrement the key reference count on that pointer. The key
  * pointer set in such way is currently understood only by
- * verify_pkcs7_signature().
+ * verify_pkcs7_signature() and verify_uasym_signature().
  *
  * Set *id* to one of the values defined in include/linux/verification.h:
  * 0 for the primary keyring (immutable keyring of system keys);
@@ -1327,6 +1327,25 @@ __bpf_kfunc void bpf_key_put(struct bpf_key *bkey)
 }
 
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
+static int validate_key(struct bpf_key *trusted_keyring)
+{
+	int ret = 0;
+
+	if (trusted_keyring->has_ref) {
+		/*
+		 * Do the permission check deferred in bpf_lookup_user_key().
+		 * See bpf_lookup_user_key() for more details.
+		 *
+		 * A call to key_task_permission() here would be redundant, as
+		 * it is already done by keyring_search() called by
+		 * find_asymmetric_key().
+		 */
+		ret = key_validate(trusted_keyring->key);
+	}
+
+	return ret;
+}
+
 /**
  * bpf_verify_pkcs7_signature - verify a PKCS#7 signature
  * @data_ptr: data to verify
@@ -1344,19 +1363,9 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 {
 	int ret;
 
-	if (trusted_keyring->has_ref) {
-		/*
-		 * Do the permission check deferred in bpf_lookup_user_key().
-		 * See bpf_lookup_user_key() for more details.
-		 *
-		 * A call to key_task_permission() here would be redundant, as
-		 * it is already done by keyring_search() called by
-		 * find_asymmetric_key().
-		 */
-		ret = key_validate(trusted_keyring->key);
-		if (ret < 0)
-			return ret;
-	}
+	ret = validate_key(trusted_keyring);
+	if (ret < 0)
+		return ret;
 
 	return verify_pkcs7_signature(data_ptr->data,
 				      __bpf_dynptr_size(data_ptr),
@@ -1366,6 +1375,36 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 				      VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
 				      NULL);
 }
+
+/**
+ * bpf_verify_uasym_signature - Verify a user asymmetric key signature
+ * @data_ptr: Data to verify
+ * @sig_ptr: Signature of the data
+ * @trusted_keyring: Keyring with keys trusted for signature verification
+ *
+ * Verify the user asymmetric key 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.
+ */
+__bpf_kfunc int bpf_verify_uasym_signature(struct bpf_dynptr_kern *data_ptr,
+					   struct bpf_dynptr_kern *sig_ptr,
+					   struct bpf_key *trusted_keyring)
+{
+	int ret;
+
+	ret = validate_key(trusted_keyring);
+	if (ret < 0)
+		return ret;
+
+	return verify_uasym_signature(data_ptr->data,
+				      __bpf_dynptr_size(data_ptr),
+				      sig_ptr->data,
+				      __bpf_dynptr_size(sig_ptr),
+				      trusted_keyring->key,
+				      VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
+				      NULL);
+}
 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 
 __diag_pop();
@@ -1376,6 +1415,7 @@ BTF_ID_FLAGS(func, bpf_lookup_system_key, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_key_put, KF_RELEASE)
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 BTF_ID_FLAGS(func, bpf_verify_pkcs7_signature, KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_verify_uasym_signature, KF_SLEEPABLE)
 #endif
 BTF_SET8_END(key_sig_kfunc_set)
 
-- 
2.34.1