X509_PUBKEY_NEW(3) | Library Functions Manual | X509_PUBKEY_NEW(3)

# NAME

`X509_PUBKEY_new`, `X509_PUBKEY_free`, `X509_PUBKEY_set`, `X509_PUBKEY_get0`, `X509_PUBKEY_get`, `d2i_X509_PUBKEY`, `i2d_X509_PUBKEY`, `d2i_PUBKEY`, `i2d_PUBKEY`, `d2i_PUBKEY_bio`, `d2i_PUBKEY_fp`, `i2d_PUBKEY_fp`, `i2d_PUBKEY_bio`, `X509_PUBKEY_set0_param`, `X509_PUBKEY_get0_param` — X.509 SubjectPublicKeyInfo structure

# SYNOPSIS

library “libcrypto”
`#include <openssl/x509.h>`

X509_PUBKEY *
`X509_PUBKEY_new`(void);

void
`X509_PUBKEY_free`(X509_PUBKEY *a);

int
`X509_PUBKEY_set`(X509_PUBKEY **x, EVP_PKEY *pkey);

EVP_PKEY *
`X509_PUBKEY_get0`(X509_PUBKEY *key);

EVP_PKEY *
`X509_PUBKEY_get`(X509_PUBKEY *key);

X509_PUBKEY *
`d2i_X509_PUBKEY`(X509_PUBKEY **val_out, const unsigned char **der_in, long length);

int
`i2d_X509_PUBKEY`(X509_PUBKEY *val_in, unsigned char **der_out);

EVP_PKEY *
`d2i_PUBKEY`(EVP_PKEY **val_out, const unsigned char **der_in, long length);

int
`i2d_PUBKEY`(EVP_PKEY *val_in, unsigned char **der_out);

EVP_PKEY *
`d2i_PUBKEY_bio`(BIO *bp, EVP_PKEY **val_out);

EVP_PKEY *
`d2i_PUBKEY_fp`(FILE *fp, EVP_PKEY **val_out);

int
`i2d_PUBKEY_fp`(FILE *fp, EVP_PKEY *val_in);

int
`i2d_PUBKEY_bio`(BIO *bp, EVP_PKEY *val_in);

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, X509_PUBKEY *pub);

# DESCRIPTION

The X509_PUBKEY structure represents the ASN.1 SubjectPublicKeyInfo structure defined in RFC 5280 section 4.1 and used in certificates and certificate requests.

`X509_PUBKEY_new`() allocates and initializes an X509_PUBKEY structure.

`X509_PUBKEY_free`() frees up the X509_PUBKEY structure a. If a is a `NULL` pointer, no action occurs.

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

`X509_PUBKEY_get0`() returns the public key contained in key. The returned value is an internal pointer which must not be freed after use.

`X509_PUBKEY_get`() is similar to `X509_PUBKEY_get0`() except that the reference count on the returned key is incremented so it must be freed using EVP_PKEY_free(3) after use.

`d2i_X509_PUBKEY`(), `i2d_X509_PUBKEY`(), `d2i_PUBKEY`(), and `i2d_PUBKEY`() decode and encode an ASN.1 SubjectPublicKeyInfo structure using either the X509_PUBKEY or the EVP_PKEY object type, respectively. For details about the semantics, examples, caveats, and bugs, see ASN1_item_d2i(3). `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 BIO or FILE pointer.

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

`X509_PUBKEY_get0_param`() retrieves the public key parameters from pub, *ppkalg is set to the associated OID and the encoding consists of *ppklen bytes at *pk, and *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.

# RETURN VALUES

If the allocation fails, `X509_PUBKEY_new`() returns `NULL` and sets an error code that can be obtained by ERR_get_error(3). Otherwise it returns a pointer to the newly allocated structure.

`X509_PUBKEY_get0`() returns an internal pointer or `NULL` if an error occurs.

`X509_PUBKEY_get`() returns a pointer to an object that had its reference count incremented or `NULL` if an error occurs.

`d2i_X509_PUBKEY`(), `d2i_PUBKEY`(), `d2i_PUBKEY_bio`(), and `d2i_PUBKEY_fp`() return a pointer to a valid object or `NULL` if an error occurs.

`i2d_X509_PUBKEY`() and `i2d_PUBKEY`() return the number of bytes successfully encoded or a negative value if an error occurs.

`X509_PUBKEY_set`(), `X509_PUBKEY_set0_param`(), `X509_PUBKEY_get0_param`(), `i2d_PUBKEY_fp`(), and `i2d_PUBKEY_bio`() return 1 for success and 0 if an error occurred.

# ERRORS

After failure of `X509_PUBKEY_get0`() or `X509_PUBKEY_get`(), one of the following diagnostics can be retrieved with ERR_get_error(3), ERR_GET_REASON(3), and ERR_reason_error_string(3):

`X509_R_UNSUPPORTED_ALGORITHM` "unsupported algorithm"
  The public key uses an algorithm unsupported by EVP_PKEY_set_type(3).
X509_R_METHOD_NOT_SUPPORTED "method not supported"
  While the algorithm is known to EVP_PKEY_set_type(3), using it for decoding is not supported.
X509_R_PUBLIC_KEY_DECODE_ERROR "public key decode error"
  Decoding the public key failed.
`ERR_R_MALLOC_FAILURE` "malloc failure"
  Memory was exhausted when trying to allocate the new EVP_PKEY object.

If key is `NULL` or does not contain a public key, these functions fail but no error is pushed onto the stack.

# SEE ALSO

d2i_X509(3), X509_ALGOR_new(3), X509_get_pubkey(3), X509_new(3)

# STANDARDS

RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile

# HISTORY

`X509_PUBKEY_new`() and `X509_PUBKEY_free`() appeared in SSLeay 0.4 or earlier. `d2i_X509_PUBKEY`() and `i2d_X509_PUBKEY`() first appeared in SSLeay 0.5.1. `X509_PUBKEY_set`() and `X509_PUBKEY_get`() first appeared in SSLeay 0.8.0. These functions have been available since OpenBSD 2.4.

`d2i_PUBKEY`() and `i2d_PUBKEY`() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7.

`d2i_PUBKEY_bio`(), `d2i_PUBKEY_fp`(), `i2d_PUBKEY_fp`(), and `i2d_PUBKEY_bio`() first appeared in OpenSSL 0.9.6 and have been available since OpenBSD 2.9.

`X509_PUBKEY_set0_param`() and `X509_PUBKEY_get0_param`() first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9.

`X509_PUBKEY_get0`() first appeared in OpenSSL 1.1.0 and has been available since OpenBSD 6.3.

June 8, 2025 | Debian