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Message-ID: <23649e1d-8fee-079a-21de-87f7024add81@meta.com>
Date: Tue, 25 Apr 2023 14:25:54 -0700
From: Yonghong Song <yhs@...a.com>
To: Roberto Sassu <roberto.sassu@...weicloud.com>, dhowells@...hat.com,
dwmw2@...radead.org, herbert@...dor.apana.org.au,
davem@...emloft.net, jarkko@...nel.org, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev,
song@...nel.org, yhs@...com, john.fastabend@...il.com,
kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
jolsa@...nel.org, rostedt@...dmis.org, mhiramat@...nel.org,
mykolal@...com, shuah@...nel.org
Cc: linux-kernel@...r.kernel.org, keyrings@...r.kernel.org,
linux-crypto@...r.kernel.org, bpf@...r.kernel.org,
linux-trace-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org,
Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [RFC][PATCH 4/6] bpf: Introduce bpf_verify_umd_signature() kfunc
On 4/25/23 10:35 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
>
> Introduce the bpf_verify_umd_signature() kfunc, to verify UMD-parsed
> signatures. The parameters and usage are the same as for
> bpf_verify_pkcs7_signature().
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
> kernel/trace/bpf_trace.c | 69 ++++++++++++++++++++++++++++++++--------
> 1 file changed, 55 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index e8da032bb6f..c9cae337596 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1271,7 +1271,7 @@ __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_umd_signature().
> *
> * Set *id* to one of the values defined in include/linux/verification.h:
> * 0 for the primary keyring (immutable keyring of system keys);
> @@ -1317,6 +1317,27 @@ __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);
> + if (ret < 0)
> + return ret;
The above
if (ret < 0)
return ret;
can be removed.
> + }
> +
> + return ret;
> +}
> +
> /**
> * bpf_verify_pkcs7_signature - verify a PKCS#7 signature
> * @data_ptr: data to verify
> @@ -1334,19 +1355,9 @@ __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_get_size(data_ptr),
> @@ -1356,6 +1367,35 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
> VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
> NULL);
> }
> +
> +/**
> + * bpf_verify_umd_signature - Verify a UMD-parsed signature
> + * @data_ptr: Data to verify
> + * @sig_ptr: Signature of the data
> + * @trusted_keyring: Keyring with keys trusted for signature verification
> + *
> + * Verify the UMD-parsed 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_umd_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_umd_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();
> @@ -1366,6 +1406,7 @@ 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_umd_signature, KF_SLEEPABLE)
> #endif
> BTF_SET8_END(key_sig_kfunc_set)
>
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