Linux currently supports RSA PKCSv1.5 encoding scheme for signing / verification. This adds support for RSASSA PSS signature verification as described in RFC8017 [1].
Patch 1 extends the x509 certificate parser to unpack PSS signature parameters. Patches 2-8 pull out the common functions / struct definitions from rsa-pkcs1pad.c into rsa-common.c, to be shared across RSA encoding scheme implementations. Patches 9, 10 provide some more plumbing to export the data needed to perform PSS operations (salt length, RSA modulus). Patches 11-16 set up PSS scaffolding and provide the verification operation per RFC8017. Patches 17, 18 turn the final knobs on to allow lowering PSS signatures for verification via keyctl. The patchset is available as a git tree at [2]. Testing: The implementation was tested by adding reference public keys to the kernel's keyring via `keyctl padd` and then verifying a known message digest / signature against this public key via `keyctl pkey_verify`. The reference vectors were taken from: - the Wycheproof testsuite [3] - FIPS 186-2 and 186-4 test vectors [4] The test harness is available at [5]. Example keyctl usage for PSS verification: rsa_bits=4096 # 2048/3072/4096 hash_algo=sha256 # sha1/sha224/sha256/sha384/sha512 saltlen=32 # Generate keys, certificate: openssl req -x509 -newkey rsa:$rsa_bits -nodes -keyout private.pem -out cert.der \ -days 100 -outform der -$hash_algo -sigopt rsa_padding_mode:pss \ -sigopt rsa_pss_saltlen:$saltlen -sigopt rsa_mgf1_md:$hash_algo # Sign data.txt: openssl dgst -${hash_algo} -sign private.pem -sigopt rsa_padding_mode:pss \ -sigopt rsa_pss_saltlen:${saltlen} -out sig.bin data.txt # Digest data.txt: openssl dgst -${hash_algo} -binary -out data.${hash_algo}.raw data.txt # Load pubkey into the kernel's keyring: kv=$(keyctl padd asymmetric "test-key" @u < cert.der) # Verify with `enc=pss`: keyctl pkey_verify $kv "0" data.${hash_algo}.raw \ sig.bin "enc=pss hash=${hash_algo} slen=${saltlen} mgfhash=${hash_algo}" v2: - Allow certificates where mgf hash algorithm is different from the digest hash algorithm. - Fix sparse warnings on "X.509: Parse RSASSA-PSS style certificates". v1 is available at [6][7]. [1] https://tools.ietf.org/html/rfc8017#section-8.1 [2] https://github.com/varadgautam/kernel/tree/rsassa-psspad-v2 [3] https://github.com/google/wycheproof/blob/master/testvectors/ [4] https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/digital-signatures#rsavs [5] https://github.com/varadgautam/keyctl-rsa-tests [6] https://lore.kernel.org/lkml/20210330202829.4825-1-varad.gau...@suse.com/ [7] https://github.com/varadgautam/kernel/tree/rsassa-psspad Varad Gautam (18): X.509: Parse RSASSA-PSS style certificates crypto: rsa-pkcs1pad: Rename pkcs1pad-specific functions to rsapad crypto: rsa-pkcs1pad: Extract pkcs1pad_create into a generic helper crypto: rsa-pkcs1pad: Pull out child req processing code into helpers crypto: rsa-pkcs1pad: Rename pkcs1pad_* structs to rsapad_* crypto: rsa: Start moving RSA common code to rsa-common crypto: rsa: Move more common code to rsa-common crypto: rsa: Move rsapad_akcipher_setup_child and callback to rsa-common crypto: Extend akcipher API to pass signature parameters crypto: rsa: Move struct rsa_mpi_key definition to rsa.h crypto: Scaffolding for RSA-PSS signature style crypto: rsa-psspad: Introduce shash alloc/dealloc helpers crypto: rsa-psspad: Get signature parameters from a given signature crypto: Implement MGF1 Mask Generation Function for RSASSA-PSS crypto: rsa-psspad: Provide PSS signature verify operation crypto: rsa-psspad: Implement signature verify callback crypto: Accept pss as valid encoding during signature verification keyctl_pkey: Add pkey parameters slen and mgfhash for PSS crypto/Kconfig | 6 + crypto/Makefile | 2 + crypto/asymmetric_keys/Makefile | 5 +- crypto/asymmetric_keys/asymmetric_type.c | 2 + crypto/asymmetric_keys/public_key.c | 18 +- crypto/asymmetric_keys/x509_cert_parser.c | 148 ++++++++ crypto/asymmetric_keys/x509_rsassa.asn1 | 17 + crypto/rsa-common.c | 291 ++++++++++++++++ crypto/rsa-pkcs1pad.c | 400 +++------------------- crypto/rsa-psspad.c | 291 ++++++++++++++++ crypto/rsa.c | 26 +- include/crypto/akcipher.h | 26 ++ include/crypto/internal/rsa-common.h | 61 ++++ include/crypto/internal/rsa.h | 10 + include/crypto/public_key.h | 4 + include/linux/keyctl.h | 2 + include/linux/oid_registry.h | 3 + security/keys/keyctl_pkey.c | 13 + 18 files changed, 961 insertions(+), 364 deletions(-) create mode 100644 crypto/asymmetric_keys/x509_rsassa.asn1 create mode 100644 crypto/rsa-common.c create mode 100644 crypto/rsa-psspad.c create mode 100644 include/crypto/internal/rsa-common.h -- 2.30.2