RSA_GET0_KEY(3ossl)

📦
version 3.5.9 · 8 versions
, in fedora 43, fedora 44

✨ RSA_GET0_KEY(3ossl) ✨

okay bestie, buckle up 💖 this is the OpenSSL manual page for all the lil getter/setter functions that poke at the insides of an RSA object — and yes, the page name is RSA_GET0_KEY(3ossl), so that's your ticket in. it's giving "group of 25 functions sharing one page" energy, and honestly? iconic.

🌸 NAME 🌸

RSA_set0_key, RSA_set0_factors, RSA_set0_crt_params, RSA_get0_key, RSA_get0_factors, RSA_get0_crt_params, RSA_get0_n, RSA_get0_e, RSA_get0_d, RSA_get0_p, RSA_get0_q, RSA_get0_dmp1, RSA_get0_dmq1, RSA_get0_iqmp, RSA_get0_pss_params, RSA_clear_flags, RSA_test_flags, RSA_set_flags, RSA_get0_engine, RSA_get_multi_prime_extra_count, RSA_get0_multi_prime_factors, RSA_get0_multi_prime_crt_params, RSA_set0_multi_prime_params, RSA_get_version — Routines for getting and setting data in an RSA object 🎀

🦋 SYNOPSIS 🦋

        #include <openssl/rsa.h>

       The following functions have been deprecated since OpenSSL 3.0, and can
       be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
       version value, see openssl_user_macros(7):

        int RSA_set0_key(RSA *r, BIGNUM *n, BIGNUM *e, BIGNUM *d);
        int RSA_set0_factors(RSA *r, BIGNUM *p, BIGNUM *q);
        int RSA_set0_crt_params(RSA *r, BIGNUM *dmp1, BIGNUM *dmq1, BIGNUM *iqmp);
        void RSA_get0_key(const RSA *r,
                          const BIGNUM **n, const BIGNUM **e, const BIGNUM **d);
        void RSA_get0_factors(const RSA *r, const BIGNUM **p, const BIGNUM **q);
        void RSA_get0_crt_params(const RSA *r,
                                 const BIGNUM **dmp1, const BIGNUM **dmq1,
                                 const BIGNUM **iqmp);
        const BIGNUM *RSA_get0_n(const RSA *d);
        const BIGNUM *RSA_get0_e(const RSA *d);
        const BIGNUM *RSA_get0_d(const RSA *d);
        const BIGNUM *RSA_get0_p(const RSA *d);
        const BIGNUM *RSA_get0_q(const RSA *d);
        const BIGNUM *RSA_get0_dmp1(const RSA *r);
        const BIGNUM *RSA_get0_dmq1(const RSA *r);
        const BIGNUM *RSA_get0_iqmp(const RSA *r);
        const RSA_PSS_PARAMS *RSA_get0_pss_params(const RSA *r);
        void RSA_clear_flags(RSA *r, int flags);
        int RSA_test_flags(const RSA *r, int flags);
        void RSA_set_flags(RSA *r, int flags);
        ENGINE *RSA_get0_engine(RSA *r);
        int RSA_get_multi_prime_extra_count(const RSA *r);
        int RSA_get0_multi_prime_factors(const RSA *r, const BIGNUM *primes[]);
        int RSA_get0_multi_prime_crt_params(const RSA *r, const BIGNUM *exps[],
                                            const BIGNUM *coeffs[]);
        int RSA_set0_multi_prime_params(RSA *r, BIGNUM *primes[], BIGNUM *exps[],
                                       BIGNUM *coeffs[], int pnum);
        int RSA_get_version(RSA *r);
⚠️ bestie, heads up: those functions have been deprecated since OpenSSL 3.0, and you can hide them entirely by defining OPENSSL_API_COMPAT with a suitable version value — peep openssl_user_macros(7) for the deets. 💅

💜 DESCRIPTION 💜

first things first, and I need you to hear me on this: all of the functions described on this page are deprecated. like, all of them. every single one. the glow-up path is to use EVP_PKEY_get_bn_param(3) for any method that hands you back a BIGNUM. and for the full tea, refer to EVP_PKEY-DH(7). periodt. 🫶

so, an RSA object is basically a lil handbag holding all the components for the public and private key: n, e, d, p, q, dmp1, dmq1 and iqmp. let's break that down:

  • n is the modulus, shared by both the public and private key
  • e is the public exponent
  • d is the private exponent
  • p, q, dmp1, dmq1 and iqmp are the factors for the second representation of a private key (see PKCS#1 section 3 Key Types), where p and q are the first and second factor of n, and dmp1, dmq1 and iqmp are the exponents and coefficient for CRT calculations

for multi-prime RSA (defined in RFC 8017), an RSA object also has one or more 'triplet's in it. a triplet contains three members: r, d and t.

  • r is the additional prime besides p and q
  • d and t are the exponent and coefficient for CRT calculations

✨ getting and setting the main three ✨

the n, e and d parameters can be obtained by calling RSA_get0_key(). if they haven't been set yet, then *n, *e and *d get set to NULL. otherwise they're set to pointers to their respective values. and here's the important bit — these point directly to the internal representations of the values, so the caller should not free them. not yours, don't touch. 🙈

the n, e and d values can be set by calling RSA_set0_key() and passing the new values for n, e and d as parameters to the function.

  • n and e must be non-NULL the first time this function is called on a given RSA object.
  • d may be NULL.
  • on subsequent calls, any of these values may be NULL, which means the corresponding RSA field is left untouched.

calling this function transfers the memory management of the values to the RSA object, so the values you passed in should not be freed by the caller after this function has been called. the object owns them now, it's their main character era. 👑

🌸 factors and CRT params 🌸

in a similar fashion:

  • the p and q parameters can be obtained and set with RSA_get0_factors() and RSA_set0_factors()
  • the dmp1, dmq1 and iqmp parameters can be obtained and set with RSA_get0_crt_params() and RSA_set0_crt_params()

for RSA_get0_key(), RSA_get0_factors(), and RSA_get0_crt_params(), NULL value BIGNUM ** output parameters are permitted. the functions ignore NULL parameters but still return values for the other, non-NULL, parameters. so you can just grab the one you want and not care about the rest. lowkey convenient. 😌

🦋 multi-prime RSA 🦋

for multi-prime RSA, RSA_get0_multi_prime_factors() and RSA_get0_multi_prime_params() can be used to obtain other primes and related CRT parameters. the return values are stored in an array of BIGNUM *.

RSA_set0_multi_prime_params() sets a collect of multi-prime 'triplet' members (prime, exponent and coefficient) into an RSA object.

💅 individual getters 💅

any of the values n, e, d, p, q, dmp1, dmq1, and iqmp can also be retrieved separately by the corresponding function, respectively:

  • RSA_get0_n()
  • RSA_get0_e()
  • RSA_get0_d()
  • RSA_get0_p()
  • RSA_get0_q()
  • RSA_get0_dmp1()
  • RSA_get0_dmq1()
  • RSA_get0_iqmp()

RSA_get0_pss_params() is used to retrieve the RSA-PSS parameters.

🎀 flags & friends 🎀

RSA_set_flags() sets the flags in the flags parameter on the RSA object. multiple flags can be passed in one go (bitwise ORed together). any flags that are already set are left set. RSA_test_flags() tests to see whether the flags passed in the flags parameter are currently set in the RSA object. multiple flags can be tested in one go. all flags that are currently set are returned, or zero if none of the flags are set. RSA_clear_flags() clears the specified flags within the RSA object.

RSA_get0_engine() returns a handle to the ENGINE that has been set for this RSA object, or NULL if no such ENGINE has been set.

RSA_get_version() returns the version of an RSA object r.

😭 NOTES 😭

values retrieved with RSA_get0_key() are owned by the RSA object used in the call and may therefore not be passed to RSA_set0_key(). if you need to, duplicate the received value using BN_dup() and pass the duplicate. the same applies to RSA_get0_factors() and RSA_set0_factors() as well as RSA_get0_crt_params() and RSA_set0_crt_params().

🫶 the caller should obtain the size by calling RSA_get_multi_prime_extra_count() in advance and allocate sufficient buffer to store the return values before calling RSA_get0_multi_prime_factors() and RSA_get0_multi_prime_params().

RSA_set0_multi_prime_params() always clears the original multi-prime triplets in RSA object r and assigns the new set of triplets into it. no keeping the old ones, it's a full rebrand. 💀

⭐ RETURN VALUES ⭐

  • RSA_set0_key(), RSA_set0_factors(), RSA_set0_crt_params() and RSA_set0_multi_prime_params() return 1 on success or 0 on failure.
  • RSA_get0_n(), RSA_get0_e(), RSA_get0_d(), RSA_get0_p(), RSA_get0_q(), RSA_get0_dmp1(), RSA_get0_dmq1(), and RSA_get0_iqmp() return the respective value.
  • RSA_get0_pss_params() returns a RSA_PSS_PARAMS pointer, or NULL if there is none.
  • RSA_get0_multi_prime_factors() and RSA_get0_multi_prime_crt_params() return 1 on success or 0 on failure.
  • RSA_get_multi_prime_extra_count() returns two less than the number of primes in use — which is 0 for traditional RSA and the number of extra primes for multi-prime RSA.
  • RSA_get_version() returns RSA_ASN1_VERSION_MULTI for multi-prime RSA and RSA_ASN1_VERSION_DEFAULT for normal two-prime RSA, as defined in RFC 8017.
  • RSA_test_flags() returns the current state of the flags in the RSA object.
  • RSA_get0_engine() returns the ENGINE set for the RSA object or NULL if no ENGINE has been set.

👀 SEE ALSO 👀

RSA_new(3), RSA_size(3)

🌈 HISTORY 🌈

  • RSA_get0_pss_params() was added in OpenSSL 1.1.1e.
  • RSA_get_multi_prime_extra_count(), RSA_get0_multi_prime_factors(), RSA_get0_multi_prime_crt_params(), RSA_set0_multi_prime_params(), and RSA_get_version() were added in OpenSSL 1.1.1.
  • the other functions described here were added in OpenSSL 1.1.0.
  • all of these functions were deprecated in OpenSSL 3.0.

Copyright 2016-2022 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

and that's the whole page bestie, no cap 💖 this one's from the OpenSSL docs, version 3.5.9, dated 2026-09-29 — go forth and not free those internal pointers, iykyk 🎀✨🦋

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