Re: [PATCH v9 07/10] bpf: Add bpf_verify_pkcs7_signature() kfunc
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2022-08-09 23:10:14
Also in:
bpf, keyrings, linux-doc, linux-kselftest, lkml
On 8/9/22 3:46 PM, Roberto Sassu wrote: [...]
quoted hunk ↗ jump to hunk
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> --- 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.
quoted hunk ↗ jump to hunk
+ 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, };