- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- SEE ALSO
- HISTORY
- COPYRIGHT

# NAME

X509_get_pubkey, X509_get0_pubkey, X509_set_pubkey, X509_get_X509_PUBKEY, X509_REQ_get_pubkey, X509_REQ_get0_pubkey, X509_REQ_set_pubkey, X509_REQ_get_X509_PUBKEY - get or set certificate or certificate request public key

# SYNOPSIS

    #include <openssl/x509.h>

    EVP_PKEY *X509_get_pubkey(const X509 *x);
    EVP_PKEY *X509_get0_pubkey(const X509 *x);
    int X509_set_pubkey(X509 *x, EVP_PKEY *pkey);
    const X509_PUBKEY *X509_get_X509_PUBKEY(const X509 *x);

    EVP_PKEY *X509_REQ_get_pubkey(X509_REQ *req);
    EVP_PKEY *X509_REQ_get0_pubkey(const X509_REQ *req);
    int X509_REQ_set_pubkey(X509_REQ *req, EVP_PKEY *pkey);
    X509_PUBKEY *X509_REQ_get_X509_PUBKEY(const X509_REQ *req);

# DESCRIPTION

X509_get_pubkey() attempts to decode the public key for certificate x. If successful it returns the public key as an EVP_PKEY pointer with its reference count incremented: this means the returned key must be freed up after use. X509_get0_pubkey() is similar except it does not increment the reference count of the returned EVP_PKEY so it must not be freed up after use.

X509_get_X509_PUBKEY() returns an internal pointer to the X509_PUBKEY structure which encodes the certificate of x. The returned value must not be freed up after use.

X509_set_pubkey() attempts to set the public key for certificate x to pkey. The key pkey should be freed up after use.

X509_REQ_get_pubkey(), X509_REQ_get0_pubkey(), X509_REQ_set_pubkey() and X509_REQ_get_X509_PUBKEY() are similar but operate on certificate request req.

# NOTES

The first time a public key is decoded the EVP_PKEY structure is cached in the certificate or certificate request itself. Subsequent calls return the cached structure with its reference count incremented to improve performance.

# RETURN VALUES

X509_get_pubkey(), X509_get0_pubkey(), X509_get_X509_PUBKEY(), X509_REQ_get_pubkey() and X509_REQ_get_X509_PUBKEY() return a public key or NULL if no public key is present in the structure or an error occurred.

X509_set_pubkey() and X509_REQ_set_pubkey() return 1 for success and 0 for failure.

# SEE ALSO

d2i_X509(3), ERR_get_error(3), X509_CRL_get0_by_serial(3), X509_get0_signature(3), X509_get_ext_d2i(3), X509_get_extension_flags(3), X509_get_subject_name(3), X509_get_version(3), X509_NAME_add_entry_by_txt(3), X509_NAME_ENTRY_get_object(3), X509_NAME_get_index_by_NID(3), X509_NAME_print_ex(3), X509_new(3), X509_sign(3), X509V3_get_d2i(3), X509_verify_cert(3)

# HISTORY

X509_REQ_get0_X509_PUBKEY() was constified in OpenSSL 4.0.

X509_get_pubkey() and X509_REQ_get_pubkey() are deprecated but retained for backward compatibility.

X509_get_pubkey() was converted to use a const parameter in OpenSSL 4.0.

# COPYRIGHT

Copyright 2015-2026 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.