RSA is an asymmetric public key algorithm that has been formalized in RFC 3447. It is in widespread use in public key infrastructures (PKI) where certificates (cf. OpenSSL::X509::Certificate) often are issued on the basis of a public/private RSA key pair. RSA is used in a wide field of applications such as secure (symmetric) key exchange, e.g. when establishing a secure TLS/SSL connection. It is also used in various digital signature schemes.

Methods
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Class Public methods
RSA.generate(size) => RSA instance
RSA.generate(size, exponent) => RSA instance

Generates an RSA keypair. size is an integer representing the desired key size. Keys smaller than 1024 should be considered insecure. exponent is an odd number normally 3, 17, or 65537.

static VALUE
ossl_rsa_s_generate(int argc, VALUE *argv, VALUE klass)
{
/* why does this method exist?  why can't initialize take an optional exponent? */
    RSA *rsa;
    VALUE size, exp;
    VALUE obj;

    rb_scan_args(argc, argv, "11", &size, &exp);

    rsa = rsa_generate(NUM2INT(size), NIL_P(exp) ? RSA_F4 : NUM2ULONG(exp)); /* err handled by rsa_instance */
    obj = rsa_instance(klass, rsa);

    if (obj == Qfalse) {
        RSA_free(rsa);
        ossl_raise(eRSAError, NULL);
    }

    return obj;
}
RSA.new(key_size) => RSA instance
RSA.new(encoded_key) => RSA instance
RSA.new(encoded_key, pass_phrase) => RSA instance

Generates or loads an RSA keypair. If an integer key_size is given it represents the desired key size. Keys less than 1024 bits should be considered insecure.

A key can instead be loaded from an encoded_key which must be PEM or DER encoded. A pass_phrase can be used to decrypt the key. If none is given OpenSSL will prompt for the pass phrase.

Examples

OpenSSL::PKey::RSA.new 2048
OpenSSL::PKey::RSA.new File.read 'rsa.pem'
OpenSSL::PKey::RSA.new File.read('rsa.pem'), 'my pass phrase'
static VALUE
ossl_rsa_initialize(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    RSA *rsa;
    BIO *in;
    VALUE arg, pass;

    GetPKey(self, pkey);
    if(rb_scan_args(argc, argv, "02", &arg, &pass) == 0) {
        rsa = RSA_new();
    }
    else if (RB_INTEGER_TYPE_P(arg)) {
        rsa = rsa_generate(NUM2INT(arg), NIL_P(pass) ? RSA_F4 : NUM2ULONG(pass));
        if (!rsa) ossl_raise(eRSAError, NULL);
    }
    else {
        pass = ossl_pem_passwd_value(pass);
        arg = ossl_to_der_if_possible(arg);
        in = ossl_obj2bio(&arg);
        rsa = PEM_read_bio_RSAPrivateKey(in, NULL, ossl_pem_passwd_cb, (void *)pass);
        if (!rsa) {
            OSSL_BIO_reset(in);
            rsa = PEM_read_bio_RSA_PUBKEY(in, NULL, NULL, NULL);
        }
        if (!rsa) {
            OSSL_BIO_reset(in);
            rsa = d2i_RSAPrivateKey_bio(in, NULL);
        }
        if (!rsa) {
            OSSL_BIO_reset(in);
            rsa = d2i_RSA_PUBKEY_bio(in, NULL);
        }
        if (!rsa) {
            OSSL_BIO_reset(in);
            rsa = PEM_read_bio_RSAPublicKey(in, NULL, NULL, NULL);
        }
        if (!rsa) {
            OSSL_BIO_reset(in);
            rsa = d2i_RSAPublicKey_bio(in, NULL);
        }
        BIO_free(in);
        if (!rsa) {
            ossl_raise(eRSAError, "Neither PUB key nor PRIV key");
        }
    }
    if (!EVP_PKEY_assign_RSA(pkey, rsa)) {
        RSA_free(rsa);
        ossl_raise(eRSAError, NULL);
    }

    return self;
}
Instance Public methods
blinding_off!()
static VALUE
ossl_rsa_blinding_off(VALUE self)
{
    RSA *rsa;

    GetRSA(self, rsa);
    RSA_blinding_off(rsa);

    return self;
}
blinding_on!()
static VALUE
ossl_rsa_blinding_on(VALUE self)
{
    RSA *rsa;

    GetRSA(self, rsa);

    if (RSA_blinding_on(rsa, ossl_bn_ctx) != 1) {
        ossl_raise(eRSAError, NULL);
    }
    return self;
}
rsa.export([cipher, pass_phrase]) => PEM-format String
rsa.to_pem([cipher, pass_phrase]) => PEM-format String
rsa.to_s([cipher, pass_phrase]) => PEM-format String

Outputs this keypair in PEM encoding. If cipher and pass_phrase are given they will be used to encrypt the key. cipher must be an OpenSSL::Cipher instance.

Also aliased as: to_pem, to_s
static VALUE
ossl_rsa_export(int argc, VALUE *argv, VALUE self)
{
    RSA *rsa;
    BIO *out;
    const EVP_CIPHER *ciph = NULL;
    VALUE cipher, pass, str;

    GetRSA(self, rsa);

    rb_scan_args(argc, argv, "02", &cipher, &pass);

    if (!NIL_P(cipher)) {
        ciph = GetCipherPtr(cipher);
        pass = ossl_pem_passwd_value(pass);
    }
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eRSAError, NULL);
    }
    if (RSA_HAS_PRIVATE(rsa)) {
        if (!PEM_write_bio_RSAPrivateKey(out, rsa, ciph, NULL, 0,
                                         ossl_pem_passwd_cb, (void *)pass)) {
            BIO_free(out);
            ossl_raise(eRSAError, NULL);
        }
    } else {
        if (!PEM_write_bio_RSA_PUBKEY(out, rsa)) {
            BIO_free(out);
            ossl_raise(eRSAError, NULL);
        }
    }
    str = ossl_membio2str(out);

    return str;
}
rsa.params => hash

THIS METHOD IS INSECURE, PRIVATE INFORMATION CAN LEAK OUT!!!

Stores all parameters of key to the hash. The hash has keys 'n', 'e', 'd', 'p', 'q', 'dmp1', 'dmq1', 'iqmp'.

Don't use :-)) (It's up to you)

static VALUE
ossl_rsa_get_params(VALUE self)
{
    RSA *rsa;
    VALUE hash;
    const BIGNUM *n, *e, *d, *p, *q, *dmp1, *dmq1, *iqmp;

    GetRSA(self, rsa);
    RSA_get0_key(rsa, &n, &e, &d);
    RSA_get0_factors(rsa, &p, &q);
    RSA_get0_crt_params(rsa, &dmp1, &dmq1, &iqmp);

    hash = rb_hash_new();
    rb_hash_aset(hash, rb_str_new2("n"), ossl_bn_new(n));
    rb_hash_aset(hash, rb_str_new2("e"), ossl_bn_new(e));
    rb_hash_aset(hash, rb_str_new2("d"), ossl_bn_new(d));
    rb_hash_aset(hash, rb_str_new2("p"), ossl_bn_new(p));
    rb_hash_aset(hash, rb_str_new2("q"), ossl_bn_new(q));
    rb_hash_aset(hash, rb_str_new2("dmp1"), ossl_bn_new(dmp1));
    rb_hash_aset(hash, rb_str_new2("dmq1"), ossl_bn_new(dmq1));
    rb_hash_aset(hash, rb_str_new2("iqmp"), ossl_bn_new(iqmp));

    return hash;
}
rsa.private? => true | false

Does this keypair contain a private key?

static VALUE
ossl_rsa_is_private(VALUE self)
{
    RSA *rsa;

    GetRSA(self, rsa);

    return RSA_PRIVATE(self, rsa) ? Qtrue : Qfalse;
}
rsa.private_decrypt(string) => String
rsa.private_decrypt(string, padding) => String

Decrypt string, which has been encrypted with the public key, with the private key. padding defaults to PKCS1_PADDING.

static VALUE
ossl_rsa_private_decrypt(int argc, VALUE *argv, VALUE self)
{
    RSA *rsa;
    const BIGNUM *rsa_n;
    int buf_len, pad;
    VALUE str, buffer, padding;

    GetRSA(self, rsa);
    RSA_get0_key(rsa, &rsa_n, NULL, NULL);
    if (!rsa_n)
        ossl_raise(eRSAError, "incomplete RSA");
    if (!RSA_PRIVATE(self, rsa))
        ossl_raise(eRSAError, "private key needed.");
    rb_scan_args(argc, argv, "11", &buffer, &padding);
    pad = (argc == 1) ? RSA_PKCS1_PADDING : NUM2INT(padding);
    StringValue(buffer);
    str = rb_str_new(0, RSA_size(rsa));
    buf_len = RSA_private_decrypt(RSTRING_LENINT(buffer), (unsigned char *)RSTRING_PTR(buffer),
                                  (unsigned char *)RSTRING_PTR(str), rsa, pad);
    if (buf_len < 0) ossl_raise(eRSAError, NULL);
    rb_str_set_len(str, buf_len);

    return str;
}
rsa.private_encrypt(string) => String
rsa.private_encrypt(string, padding) => String

Encrypt string with the private key. padding defaults to PKCS1_PADDING. The encrypted string output can be decrypted using public_decrypt.

static VALUE
ossl_rsa_private_encrypt(int argc, VALUE *argv, VALUE self)
{
    RSA *rsa;
    const BIGNUM *rsa_n;
    int buf_len, pad;
    VALUE str, buffer, padding;

    GetRSA(self, rsa);
    RSA_get0_key(rsa, &rsa_n, NULL, NULL);
    if (!rsa_n)
        ossl_raise(eRSAError, "incomplete RSA");
    if (!RSA_PRIVATE(self, rsa))
        ossl_raise(eRSAError, "private key needed.");
    rb_scan_args(argc, argv, "11", &buffer, &padding);
    pad = (argc == 1) ? RSA_PKCS1_PADDING : NUM2INT(padding);
    StringValue(buffer);
    str = rb_str_new(0, RSA_size(rsa));
    buf_len = RSA_private_encrypt(RSTRING_LENINT(buffer), (unsigned char *)RSTRING_PTR(buffer),
                                  (unsigned char *)RSTRING_PTR(str), rsa, pad);
    if (buf_len < 0) ossl_raise(eRSAError, NULL);
    rb_str_set_len(str, buf_len);

    return str;
}
rsa.public? => true

The return value is always true since every private key is also a public key.

static VALUE
ossl_rsa_is_public(VALUE self)
{
    RSA *rsa;

    GetRSA(self, rsa);
    /*
     * This method should check for n and e.  BUG.
     */
    (void)rsa;
    return Qtrue;
}
rsa.public_decrypt(string) => String
rsa.public_decrypt(string, padding) => String

Decrypt string, which has been encrypted with the private key, with the public key. padding defaults to PKCS1_PADDING.

static VALUE
ossl_rsa_public_decrypt(int argc, VALUE *argv, VALUE self)
{
    RSA *rsa;
    const BIGNUM *rsa_n;
    int buf_len, pad;
    VALUE str, buffer, padding;

    GetRSA(self, rsa);
    RSA_get0_key(rsa, &rsa_n, NULL, NULL);
    if (!rsa_n)
        ossl_raise(eRSAError, "incomplete RSA");
    rb_scan_args(argc, argv, "11", &buffer, &padding);
    pad = (argc == 1) ? RSA_PKCS1_PADDING : NUM2INT(padding);
    StringValue(buffer);
    str = rb_str_new(0, RSA_size(rsa));
    buf_len = RSA_public_decrypt(RSTRING_LENINT(buffer), (unsigned char *)RSTRING_PTR(buffer),
                                 (unsigned char *)RSTRING_PTR(str), rsa, pad);
    if (buf_len < 0) ossl_raise(eRSAError, NULL);
    rb_str_set_len(str, buf_len);

    return str;
}
rsa.public_encrypt(string) => String
rsa.public_encrypt(string, padding) => String

Encrypt string with the public key. padding defaults to PKCS1_PADDING. The encrypted string output can be decrypted using private_decrypt.

static VALUE
ossl_rsa_public_encrypt(int argc, VALUE *argv, VALUE self)
{
    RSA *rsa;
    const BIGNUM *rsa_n;
    int buf_len, pad;
    VALUE str, buffer, padding;

    GetRSA(self, rsa);
    RSA_get0_key(rsa, &rsa_n, NULL, NULL);
    if (!rsa_n)
        ossl_raise(eRSAError, "incomplete RSA");
    rb_scan_args(argc, argv, "11", &buffer, &padding);
    pad = (argc == 1) ? RSA_PKCS1_PADDING : NUM2INT(padding);
    StringValue(buffer);
    str = rb_str_new(0, RSA_size(rsa));
    buf_len = RSA_public_encrypt(RSTRING_LENINT(buffer), (unsigned char *)RSTRING_PTR(buffer),
                                 (unsigned char *)RSTRING_PTR(str), rsa, pad);
    if (buf_len < 0) ossl_raise(eRSAError, NULL);
    rb_str_set_len(str, buf_len);

    return str;
}
rsa.public_key → RSA

Makes new RSA instance containing the public key from the private key.

static VALUE
ossl_rsa_to_public_key(VALUE self)
{
    EVP_PKEY *pkey;
    RSA *rsa;
    VALUE obj;

    GetPKeyRSA(self, pkey);
    /* err check performed by rsa_instance */
    rsa = RSAPublicKey_dup(EVP_PKEY_get0_RSA(pkey));
    obj = rsa_instance(rb_obj_class(self), rsa);
    if (obj == Qfalse) {
        RSA_free(rsa);
        ossl_raise(eRSAError, NULL);
    }
    return obj;
}
rsa.set_crt_params(dmp1, dmq1, iqmp) → self

Sets dmp1, dmq1, iqmp for the RSA instance. They are calculated by d mod (p - 1), d mod (q - 1) and q^(-1) mod p respectively.

rsa.set_factors(p, q) → self

Sets p, q for the RSA instance.

rsa.set_key(n, e, d) → self

Sets n, e, d for the RSA instance.

rsa.to_der => DER-format String

Outputs this keypair in DER encoding.

static VALUE
ossl_rsa_to_der(VALUE self)
{
    RSA *rsa;
    int (*i2d_func)(const RSA *, unsigned char **);
    unsigned char *p;
    long len;
    VALUE str;

    GetRSA(self, rsa);
    if (RSA_HAS_PRIVATE(rsa))
        i2d_func = i2d_RSAPrivateKey;
    else
        i2d_func = (int (*)(const RSA *, unsigned char **))i2d_RSA_PUBKEY;
    if((len = i2d_func(rsa, NULL)) <= 0)
        ossl_raise(eRSAError, NULL);
    str = rb_str_new(0, len);
    p = (unsigned char *)RSTRING_PTR(str);
    if(i2d_func(rsa, &p) < 0)
        ossl_raise(eRSAError, NULL);
    ossl_str_adjust(str, p);

    return str;
}
to_pem(p1 = v1, p2 = v2)
Alias for: export
to_s(p1 = v1, p2 = v2)
Alias for: export
rsa.to_text => String

THIS METHOD IS INSECURE, PRIVATE INFORMATION CAN LEAK OUT!!!

Dumps all parameters of a keypair to a String

Don't use :-)) (It's up to you)

static VALUE
ossl_rsa_to_text(VALUE self)
{
    RSA *rsa;
    BIO *out;
    VALUE str;

    GetRSA(self, rsa);
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eRSAError, NULL);
    }
    if (!RSA_print(out, rsa, 0)) { /* offset = 0 */
        BIO_free(out);
        ossl_raise(eRSAError, NULL);
    }
    str = ossl_membio2str(out);

    return str;
}