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=head1 NAME

X509_PUBKEY_new, X509_PUBKEY_free, X509_PUBKEY_dup,
X509_PUBKEY_set, X509_PUBKEY_get0, X509_PUBKEY_get,
d2i_PUBKEY_ex, d2i_PUBKEY, i2d_PUBKEY, d2i_PUBKEY_bio, d2i_PUBKEY_fp,
i2d_PUBKEY_fp, i2d_PUBKEY_bio, X509_PUBKEY_set0_param, X509_PUBKEY_get0_param,
X509_PUBKEY_eq - SubjectPublicKeyInfo public key functions

=head1 SYNOPSIS

 #include <openssl/x509.h>

 X509_PUBKEY *X509_PUBKEY_new(void);
 void X509_PUBKEY_free(X509_PUBKEY *a);
 X509_PUBKEY *X509_PUBKEY_dup(const X509_PUBKEY *a);

 int X509_PUBKEY_set(X509_PUBKEY **x, EVP_PKEY *pkey);
 EVP_PKEY *X509_PUBKEY_get0(const X509_PUBKEY *key);
 EVP_PKEY *X509_PUBKEY_get(const X509_PUBKEY *key);

 EVP_PKEY *d2i_PUBKEY_ex(EVP_PKEY **a, const unsigned char **pp, long length,
                         OSSL_LIB_CTX *libctx, const char *propq);
 EVP_PKEY *d2i_PUBKEY(EVP_PKEY **a, const unsigned char **pp, long length);
 int i2d_PUBKEY(const EVP_PKEY *a, unsigned char **pp);

 EVP_PKEY *d2i_PUBKEY_bio(BIO *bp, EVP_PKEY **a);
 EVP_PKEY *d2i_PUBKEY_fp(FILE *fp, EVP_PKEY **a);

 int i2d_PUBKEY_fp(const FILE *fp, EVP_PKEY *pkey);
 int i2d_PUBKEY_bio(BIO *bp, const EVP_PKEY *pkey);

 int X509_PUBKEY_set0_param(X509_PUBKEY *pub, ASN1_OBJECT *aobj,
                            int ptype, void *pval,
                            unsigned char *penc, int penclen);
 int X509_PUBKEY_get0_param(ASN1_OBJECT **ppkalg,
                            const unsigned char **pk, int *ppklen,
                            X509_ALGOR **pa, const X509_PUBKEY *pub);
 int X509_PUBKEY_eq(X509_PUBKEY *a, X509_PUBKEY *b);

=head1 DESCRIPTION

The B<X509_PUBKEY> structure represents the ASN.1 B<SubjectPublicKeyInfo>
structure defined in RFC5280 and used in certificates and certificate requests.

X509_PUBKEY_new() allocates and initializes an B<X509_PUBKEY> structure.

X509_PUBKEY_dup() creates a duplicate copy of the B<X509_PUBKEY> object
specified by I<a>.

X509_PUBKEY_free() frees up B<X509_PUBKEY> structure I<a>. If I<a> is NULL
nothing is done.

X509_PUBKEY_set() sets the public key in I<*x> to the public key contained
in the B<EVP_PKEY> structure I<pkey>. If I<*x> is not NULL any existing
public key structure will be freed.

X509_PUBKEY_get0() returns the public key contained in I<key>. The returned
value is an internal pointer which B<MUST NOT> be freed after use.

X509_PUBKEY_get() is similar to X509_PUBKEY_get0() except the reference
count on the returned key is incremented so it B<MUST> be freed using
EVP_PKEY_free() after use.

d2i_PUBKEY_ex() decodes an B<EVP_PKEY> structure using B<SubjectPublicKeyInfo>
format.  Some public key decoding implementations may use cryptographic
algorithms. In this case the supplied library context I<libctx> and property
query string I<propq> are used.
d2i_PUBKEY() does the same as d2i_PUBKEY_ex() except that the default
library context and property query string are used.

i2d_PUBKEY() encodes an B<EVP_PKEY> structure using B<SubjectPublicKeyInfo>
format.

d2i_PUBKEY_bio(), d2i_PUBKEY_fp(), i2d_PUBKEY_bio() and i2d_PUBKEY_fp() are
similar to d2i_PUBKEY() and i2d_PUBKEY() except they decode or encode using a
B<BIO> or B<FILE> pointer.

X509_PUBKEY_set0_param() sets the public key parameters of I<pub>. The
OID associated with the algorithm is set to I<aobj>. The type of the
algorithm parameters is set to I<type> using the structure I<pval>.
The encoding of the public key itself is set to the I<penclen>
bytes contained in buffer I<penc>. On success ownership of all the supplied
parameters is passed to I<pub> so they must not be freed after the
call.

X509_PUBKEY_get0_param() retrieves the public key parameters from I<pub>,
I<*ppkalg> is set to the associated OID and the encoding consists of
I<*ppklen> bytes at I<*pk>, I<*pa> is set to the associated
AlgorithmIdentifier for the public key. If the value of any of these
parameters is not required it can be set to NULL. All of the
retrieved pointers are internal and must not be freed after the
call.

X509_PUBKEY_eq() compares two B<X509_PUBKEY> values.

=head1 NOTES

The B<X509_PUBKEY> functions can be used to encode and decode public keys
in a standard format.

In many cases applications will not call the B<X509_PUBKEY> functions
directly: they will instead call wrapper functions such as X509_get0_pubkey().

=head1 RETURN VALUES

If the allocation fails, X509_PUBKEY_new() and X509_PUBKEY_dup() return
NULL and set an error code that can be obtained by L<ERR_get_error(3)>.
Otherwise they return a pointer to the newly allocated structure.

X509_PUBKEY_free() does not return a value.

X509_PUBKEY_get0() and X509_PUBKEY_get() return a pointer to an B<EVP_PKEY>
structure or NULL if an error occurs.

X509_PUBKEY_set(), X509_PUBKEY_set0_param() and X509_PUBKEY_get0_param()
return 1 for success and 0 if an error occurred.

X509_PUBKEY_eq() returns 1 for equal, 0 for different, and < 0 on error.

=head1 SEE ALSO

L<d2i_X509(3)>,
L<ERR_get_error(3)>,
L<X509_get_pubkey(3)>,

=head1 HISTORY

The X509_PUBKEY_eq() function was added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2016-2021 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
L<https://www.openssl.org/source/license.html>.

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