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Message-ID: <ade93f7324c5f07511a0793f702024d41889636d.camel@huaweicloud.com>
Date: Wed, 26 Apr 2023 13:44:09 +0200
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Yonghong Song <yhs@...a.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 Tue, 2023-04-25 at 14:25 -0700, Yonghong Song wrote:
>
> 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.
Right, thanks!
Roberto
> > + }
> > +
> > + 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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