The kernel RSA ASN.1 private key parser already supports only private keys with additional values to be used with the Chinese Remainder Theorem [1], but these values are currently not used. This rudimentary CRT implementation speeds up RSA private key operations for the following Go benchmark up to ~3x. This implementation also tries to minimise the allocation of additional MPIs, so existing MPIs are reused as much as possible (hence the variable names are a bit weird). The benchmark used: ``` package keyring_test import ( "crypto" "crypto/rand" "crypto/rsa" "crypto/x509" "io" "syscall" "testing" "unsafe" ) type KeySerial int32 type Keyring int32 const ( KEY_SPEC_PROCESS_KEYRING Keyring = -2 KEYCTL_PKEY_SIGN = 27 ) var ( keyTypeAsym = []byte("asymmetric\x00") sha256pkcs1 = []byte("enc=pkcs1 hash=sha256\x00") ) func (keyring Keyring) LoadAsym(desc string, payload []byte) (KeySerial, error) { cdesc := []byte(desc + "\x00") serial, _, errno := syscall.Syscall6(syscall.SYS_ADD_KEY, uintptr(unsafe.Pointer(&keyTypeAsym[0])), uintptr(unsafe.Pointer(&cdesc[0])), uintptr(unsafe.Pointer(&payload[0])), uintptr(len(payload)), uintptr(keyring), uintptr(0)) if errno == 0 { return KeySerial(serial), nil } return KeySerial(serial), errno } type pkeyParams struct { key_id KeySerial in_len uint32 out_or_in2_len uint32 __spare [7]uint32 } // the output signature buffer is an input parameter here, because we want to // avoid Go buffer allocation leaking into our benchmarks func (key KeySerial) Sign(info, digest, out []byte) error { var params pkeyParams params.key_id = key params.in_len = uint32(len(digest)) params.out_or_in2_len = uint32(len(out)) _, _, errno := syscall.Syscall6(syscall.SYS_KEYCTL, KEYCTL_PKEY_SIGN, uintptr(unsafe.Pointer(¶ms)), uintptr(unsafe.Pointer(&info[0])), uintptr(unsafe.Pointer(&digest[0])), uintptr(unsafe.Pointer(&out[0])), uintptr(0)) if errno == 0 { return nil } return errno } func BenchmarkSign(b *testing.B) { priv, err := rsa.GenerateKey(rand.Reader, 2048) if err != nil { b.Fatalf("failed to generate private key: %v", err) } pkcs8, err := x509.MarshalPKCS8PrivateKey(priv) if err != nil { b.Fatalf("failed to serialize the private key to PKCS8 blob: %v", err) } serial, err := KEY_SPEC_PROCESS_KEYRING.LoadAsym("test rsa key", pkcs8) if err != nil { b.Fatalf("failed to load the private key into the keyring: %v", err) } b.Logf("loaded test rsa key: %v", serial) digest := make([]byte, 32) _, err = io.ReadFull(rand.Reader, digest) if err != nil { b.Fatalf("failed to generate a random digest: %v", err) } sig := make([]byte, 256) for n := 0; n < b.N; n++ { err = serial.Sign(sha256pkcs1, digest, sig) if err != nil { b.Fatalf("failed to sign the digest: %v", err) } } err = rsa.VerifyPKCS1v15(&priv.PublicKey, crypto.SHA256, digest, sig) if err != nil { b.Fatalf("failed to verify the signature: %v", err) } } ``` [1]: https://en.wikipedia.org/wiki/RSA_(cryptosystem)#Using_the_Chinese_remainder_algorithm Signed-off-by: Ignat Korchagin <ignat@xxxxxxxxxxxxxx> --- crypto/rsa.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 73 insertions(+), 5 deletions(-) diff --git a/crypto/rsa.c b/crypto/rsa.c index 39e04176b04b..0e555ee4addb 100644 --- a/crypto/rsa.c +++ b/crypto/rsa.c @@ -17,6 +17,11 @@ struct rsa_mpi_key { MPI n; MPI e; MPI d; + MPI p; + MPI q; + MPI dp; + MPI dq; + MPI qinv; }; /* @@ -35,16 +40,49 @@ static int _rsa_enc(const struct rsa_mpi_key *key, MPI c, MPI m) /* * RSADP function [RFC3447 sec 5.1.2] - * m = c^d mod n; + * m_1 = c^dP mod p; + * m_2 = c^dQ mod q; + * h = (m_1 - m_2) * qInv mod p; + * m = m_2 + q * h; */ -static int _rsa_dec(const struct rsa_mpi_key *key, MPI m, MPI c) +static int _rsa_dec_crt(const struct rsa_mpi_key *key, MPI m_or_m1_or_h, MPI c) { + MPI m2, m12_or_qh; + int ret = -ENOMEM; + /* (1) Validate 0 <= c < n */ if (mpi_cmp_ui(c, 0) < 0 || mpi_cmp(c, key->n) >= 0) return -EINVAL; - /* (2) m = c^d mod n */ - return mpi_powm(m, c, key->d, key->n); + m2 = mpi_alloc(0); + m12_or_qh = mpi_alloc(0); + if (!m2 || !m12_or_qh) + goto err_free_mpi; + + /* (2i) m_1 = c^dP mod p */ + ret = mpi_powm(m_or_m1_or_h, c, key->dp, key->p); + if (ret) + goto err_free_mpi; + + /* (2i) m_2 = c^dQ mod q */ + ret = mpi_powm(m2, c, key->dq, key->q); + if (ret) + goto err_free_mpi; + + /* (2iii) h = (m_1 - m_2) * qInv mod p */ + mpi_sub(m12_or_qh, m_or_m1_or_h, m2); + mpi_mulm(m_or_m1_or_h, m12_or_qh, key->qinv, key->p); + + /* (2iv) m = m_2 + q * h */ + mpi_mul(m12_or_qh, key->q, m_or_m1_or_h); + mpi_addm(m_or_m1_or_h, m2, m12_or_qh, key->n); + + ret = 0; + +err_free_mpi: + mpi_free(m12_or_qh); + mpi_free(m2); + return ret; } static inline struct rsa_mpi_key *rsa_get_key(struct crypto_akcipher *tfm) @@ -112,7 +150,7 @@ static int rsa_dec(struct akcipher_request *req) if (!c) goto err_free_m; - ret = _rsa_dec(pkey, m, c); + ret = _rsa_dec_crt(pkey, m, c); if (ret) goto err_free_c; @@ -134,9 +172,19 @@ static void rsa_free_mpi_key(struct rsa_mpi_key *key) mpi_free(key->d); mpi_free(key->e); mpi_free(key->n); + mpi_free(key->p); + mpi_free(key->q); + mpi_free(key->dp); + mpi_free(key->dq); + mpi_free(key->qinv); key->d = NULL; key->e = NULL; key->n = NULL; + key->p = NULL; + key->q = NULL; + key->dp = NULL; + key->dq = NULL; + key->qinv = NULL; } static int rsa_check_key_length(unsigned int len) @@ -217,6 +265,26 @@ static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key, if (!mpi_key->n) goto err; + mpi_key->p = mpi_read_raw_data(raw_key.p, raw_key.p_sz); + if (!mpi_key->p) + goto err; + + mpi_key->q = mpi_read_raw_data(raw_key.q, raw_key.q_sz); + if (!mpi_key->q) + goto err; + + mpi_key->dp = mpi_read_raw_data(raw_key.dp, raw_key.dp_sz); + if (!mpi_key->dp) + goto err; + + mpi_key->dq = mpi_read_raw_data(raw_key.dq, raw_key.dq_sz); + if (!mpi_key->dq) + goto err; + + mpi_key->qinv = mpi_read_raw_data(raw_key.qinv, raw_key.qinv_sz); + if (!mpi_key->qinv) + goto err; + if (rsa_check_key_length(mpi_get_size(mpi_key->n) << 3)) { rsa_free_mpi_key(mpi_key); return -EINVAL; -- 2.36.1