From: Roberto Sassu <roberto.sa...@huawei.com> Support for PGP keys and signatures was proposed by David long time ago, before the decision of using PKCS#7 for kernel modules signatures verification was made. After that, there has been not enough interest to support PGP too.
Lately, when discussing a proposal of introducing fsverity signatures in Fedora [1], developers expressed their preference on not having a separate key for signing, which would complicate the management of the distribution. They would be more in favor of using the same PGP key, currently used for signing RPM headers, also for file-based signatures (not only fsverity, but also IMA ones). Another envisioned use case would be to add the ability to appraise RPM headers with their existing PGP signature, so that they can be used as an authenticated source of reference values for appraising remaining files [2]. To make these use cases possible, introduce support for PGP keys and signatures in the kernel, and load provided PGP keys in the built-in keyring, so that PGP signatures of RPM headers, fsverity digests, and IMA digests can be verified from this trust anchor. In addition to the original version of the patch set, also introduce support for signature verification of PGP keys, so that those keys can be added to keyrings with a signature-based restriction (e.g. .ima). PGP keys are searched with partial IDs, provided with signature subtype 16 (Issuer). Search with full IDs could be supported with draft-ietf-openpgp-rfc4880bis-10, by retrieving the information from signature subtype 33 (Issuer Fingerprint). Due to the possibility of ID collisions, the key_or_keyring restriction is not supported. The patch set includes two preliminary patches: patch 1 introduces mpi_key_length(), to get the number of bits and bytes of an MPI; patch 2 introduces rsa_parse_priv_key_raw() and rsa_parse_pub_key_raw(), to parse an RSA key in RAW format if the ASN.1 parser returns an error. Patches 3-5 introduce the library necessary to parse PGP keys and signatures, whose support is added with patches 6-10. Patch 11 introduces verify_pgp_signature() to be used by kernel subsystems (e.g. fsverity and IMA). Patch 12 is for testing of PGP signatures. Finally, patches 13-14 allow loading a set of PGP keys from a supplied blob at boot time. Changelog v1 [4]: - Remove quiet_cmd_extract_certs (redundant, likely leftover from conflict resolution) - Load PGP keys embedded in the kernel image within load_module_cert() and load_system_certificate_list(), instead of using a separate initcall - Style bug fixes found by checkpatch.pl - Add <crypto/pgp.h> include in crypto/asymmetric_keys/pgp_preload.c, to remove no previous prototype warning - Correctly check returned tfm in pgp_generate_fingerprint() - Fix printing message in pgp_generate_fingerprint() - Don't create a public key if the key blob does not contain a PGP key packet - Remove unused pgp_pubkey_hash array - Set KEY_EFLAG_DIGITALSIG key flag if the key has the capability - Allow PGP_SIG_GENERAL_CERT_OF_UID_PUBKEY signature type (for key sigs) - Add is_key_sig parameter to pgp_sig_get_sig() to ensure the key signature type is PGP_SIG_GENERAL_CERT_OF_UID_PUBKEY or PGP_SIG_POSTITIVE_CERT_OF_UID_PUBKEY v0 [3]: - style fixes - move include/linux/pgp.h and pgplib.h to crypto/asymmetric_keys - introduce verify_pgp_signature() - replace KEY_ALLOC_TRUSTED flag with KEY_ALLOC_BUILT_IN - don't fetch PGP subkeys - drop support for DSA - store number of MPIs in pgp_key_algo_p_num_mpi array - replace dynamic memory allocations with static ones in pgp_generate_fingerprint() - store only keys with capability of verifying signatures - remember selection of PGP signature packet and don't repeat parsing - move search of the PGP key to verify the signature from the beginning to the end of the verification process (to be similar with PKCS#7) - don't retry key search in the session keyring from the signature verification code, let the caller pass the desired keyring - for the PGP signature test key type, retry the key search in the session keyring - retry key search in restrict_link_by_signature() with a partial ID (provided in the PGP signature) [1] https://fedoraproject.org/wiki/Changes/FsVerityRPM [2] https://lore.kernel.org/linux-integrity/20240415142436.2545003-1-roberto.sa...@huaweicloud.com/ [3] https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-modsign.git/log/?h=pgp-parser [4] https://lore.kernel.org/linux-integrity/20220111180318.591029-1-roberto.sa...@huawei.com/ David Howells (8): PGPLIB: PGP definitions (RFC 4880) PGPLIB: Basic packet parser PGPLIB: Signature parser KEYS: PGP data parser KEYS: Provide PGP key description autogeneration KEYS: PGP-based public key signature verification PGP: Provide a key type for testing PGP signatures KEYS: Provide a function to load keys from a PGP keyring blob Roberto Sassu (6): mpi: Introduce mpi_key_length() rsa: add parser of raw format KEYS: Retry asym key search with partial ID in restrict_link_by_signature() KEYS: Calculate key digest and get signature of the key verification: introduce verify_pgp_signature() KEYS: Introduce load_pgp_public_keyring() MAINTAINERS | 1 + certs/Kconfig | 11 + certs/Makefile | 7 + certs/system_certificates.S | 18 + certs/system_keyring.c | 93 ++++ crypto/asymmetric_keys/Kconfig | 38 ++ crypto/asymmetric_keys/Makefile | 13 + crypto/asymmetric_keys/pgp.h | 206 ++++++++ crypto/asymmetric_keys/pgp_library.c | 620 ++++++++++++++++++++++++ crypto/asymmetric_keys/pgp_parser.h | 18 + crypto/asymmetric_keys/pgp_preload.c | 111 +++++ crypto/asymmetric_keys/pgp_public_key.c | 492 +++++++++++++++++++ crypto/asymmetric_keys/pgp_signature.c | 505 +++++++++++++++++++ crypto/asymmetric_keys/pgp_test_key.c | 129 +++++ crypto/asymmetric_keys/pgplib.h | 74 +++ crypto/asymmetric_keys/restrict.c | 10 +- crypto/rsa.c | 14 +- crypto/rsa_helper.c | 69 +++ include/crypto/internal/rsa.h | 6 + include/crypto/pgp.h | 36 ++ include/linux/mpi.h | 2 + include/linux/verification.h | 23 + lib/crypto/mpi/mpicoder.c | 33 +- 23 files changed, 2516 insertions(+), 13 deletions(-) create mode 100644 crypto/asymmetric_keys/pgp.h create mode 100644 crypto/asymmetric_keys/pgp_library.c create mode 100644 crypto/asymmetric_keys/pgp_parser.h create mode 100644 crypto/asymmetric_keys/pgp_preload.c create mode 100644 crypto/asymmetric_keys/pgp_public_key.c create mode 100644 crypto/asymmetric_keys/pgp_signature.c create mode 100644 crypto/asymmetric_keys/pgp_test_key.c create mode 100644 crypto/asymmetric_keys/pgplib.h create mode 100644 include/crypto/pgp.h -- 2.34.1
