Messages in this thread | | | Subject | Re: [PATCH v2 1/3] bpf: Add bpf_verify_pkcs7_signature() helper | From | Daniel Borkmann <> | Date | Wed, 8 Jun 2022 16:43:12 +0200 |
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On 6/8/22 1:12 PM, Roberto Sassu wrote: > Add the bpf_verify_pkcs7_signature() helper, to give the ability to eBPF > security modules to check the validity of a PKCS#7 signature against > supplied data. > > Use the 'keyring' parameter to select the keyring containing the > verification key: 0 for the primary keyring, 1 for the primary and > secondary keyrings, 2 for the platform keyring. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > include/uapi/linux/bpf.h | 8 ++++++++ > kernel/bpf/bpf_lsm.c | 32 ++++++++++++++++++++++++++++++++ > tools/include/uapi/linux/bpf.h | 8 ++++++++ > 3 files changed, 48 insertions(+) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index f4009dbdf62d..40d0fc0d9493 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -5249,6 +5249,13 @@ union bpf_attr { > * Pointer to the underlying dynptr data, NULL if the dynptr is > * read-only, if the dynptr is invalid, or if the offset and length > * is out of bounds. > + * > + * long bpf_verify_pkcs7_signature(u8 *data, u32 datalen, u8 *sig, u32 siglen, u64 keyring) > + * Description > + * Verify the PKCS#7 *sig* with length *siglen*, on *data* with > + * length *datalen*, with key in *keyring*.
Could you also add a description for users about the keyring argument and guidance on when they should use which in their programs? Above is a bit too terse, imho.
> + * Return > + * 0 on success, a negative value on error. > */ > #define __BPF_FUNC_MAPPER(FN) \ > FN(unspec), \ > @@ -5455,6 +5462,7 @@ union bpf_attr { > FN(dynptr_read), \ > FN(dynptr_write), \ > FN(dynptr_data), \ > + FN(verify_pkcs7_signature), \ > /* */ > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c > index c1351df9f7ee..1cda43cb541a 100644 > --- a/kernel/bpf/bpf_lsm.c > +++ b/kernel/bpf/bpf_lsm.c > @@ -16,6 +16,7 @@ > #include <linux/bpf_local_storage.h> > #include <linux/btf_ids.h> > #include <linux/ima.h> > +#include <linux/verification.h> > > /* For every LSM hook that allows attachment of BPF programs, declare a nop > * function where a BPF program can be attached. > @@ -132,6 +133,35 @@ static const struct bpf_func_proto bpf_get_attach_cookie_proto = { > .arg1_type = ARG_PTR_TO_CTX, > }; > > +BPF_CALL_5(bpf_verify_pkcs7_signature, u8 *, data, u32, datalen, u8 *, sig, > + u32, siglen, u64, keyring) > +{ > + int ret = -EOPNOTSUPP; > + > +#ifdef CONFIG_SYSTEM_DATA_VERIFICATION > + if (keyring > (unsigned long)VERIFY_USE_PLATFORM_KEYRING) > + return -EINVAL; > + > + ret = verify_pkcs7_signature(data, datalen, sig, siglen, > + (struct key *)keyring, > + VERIFYING_UNSPECIFIED_SIGNATURE, NULL, > + NULL); > +#endif > + return ret; > +}
Looks great! One small nit, I would move all of the BPF_CALL and _proto under the #ifdef CONFIG_SYSTEM_DATA_VERIFICATION ...
> +static const struct bpf_func_proto bpf_verify_pkcs7_signature_proto = { > + .func = bpf_verify_pkcs7_signature, > + .gpl_only = false, > + .ret_type = RET_INTEGER, > + .arg1_type = ARG_PTR_TO_MEM, > + .arg2_type = ARG_CONST_SIZE_OR_ZERO, > + .arg3_type = ARG_PTR_TO_MEM, > + .arg4_type = ARG_CONST_SIZE_OR_ZERO, > + .arg5_type = ARG_ANYTHING, > + .allowed = bpf_ima_inode_hash_allowed, > +}; > + > static const struct bpf_func_proto * > bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > { > @@ -158,6 +188,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > return prog->aux->sleepable ? &bpf_ima_file_hash_proto : NULL; > case BPF_FUNC_get_attach_cookie: > return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto : NULL; > + case BPF_FUNC_verify_pkcs7_signature: > + return prog->aux->sleepable ? &bpf_verify_pkcs7_signature_proto : NULL;
... same here:
#ifdef CONFIG_SYSTEM_DATA_VERIFICATION case BPF_FUNC_verify_pkcs7_signature: return prog->aux->sleepable ? &bpf_verify_pkcs7_signature_proto : NULL; #endif
So that bpftool or other feature probes can check for its availability. Otherwise, apps have a hard time checking whether bpf_verify_pkcs7_signature() helper is available for use or not.
> default: > return tracing_prog_func_proto(func_id, prog); > } > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > index f4009dbdf62d..40d0fc0d9493 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -5249,6 +5249,13 @@ union bpf_attr { > * Pointer to the underlying dynptr data, NULL if the dynptr is > * read-only, if the dynptr is invalid, or if the offset and length > * is out of bounds. > + * > + * long bpf_verify_pkcs7_signature(u8 *data, u32 datalen, u8 *sig, u32 siglen, u64 keyring) > + * Description > + * Verify the PKCS#7 *sig* with length *siglen*, on *data* with > + * length *datalen*, with key in *keyring*. > + * Return > + * 0 on success, a negative value on error. > */ > #define __BPF_FUNC_MAPPER(FN) \ > FN(unspec), \ > @@ -5455,6 +5462,7 @@ union bpf_attr { > FN(dynptr_read), \ > FN(dynptr_write), \ > FN(dynptr_data), \ > + FN(verify_pkcs7_signature), \ > /* */ > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper >
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