X509_PUBKEY_NEW(3)

📦 version 4.4.0, in alpine 3.24, arch rolling

💖 NAME 💖

okay so bestie, welcome to X509_PUBKEY_NEW(3) from the Library Functions Manual — this is the whole squad: 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 — all about the X.509 SubjectPublicKeyInfo structure. periodt 💅

🌸 SYNOPSIS 🌸

first things first: you're on libcrypto energy, and you're pulling in <openssl/x509.h>. here's the whole function lineup, exactly as it is:

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. it's literally the main character of public-key packaging, no cap 🔥

  • X509_PUBKEY_new() — allocates and initializes an X509_PUBKEY structure. fresh out the box ✨
  • X509_PUBKEY_free() — frees up the X509_PUBKEY structure a. If a is a NULL pointer, no action occurs. so if a is NULL, it's giving "nothing to see here" 💀
  • 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. it's a glow-up with cleanup 🧚
  • X509_PUBKEY_get0() — returns the public key contained in key. The returned value is an internal pointer which must not be freed after use.
bestie, that "internal pointer" part is serious: do not free it after use. it's borrowed, not yours 💅
  • X509_PUBKEY_get() — 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. so this one is yours to clean up 🫶
  • 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() — similar to d2i_PUBKEY() and i2d_PUBKEY() except they decode or encode using a BIO or FILE pointer. same vibe, different I/O bestie 🎀
  • 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.
okay this is the big one: on success, ownership of all the supplied parameters is passed to pub, so you must not free them after the call. not even a little. not even ironically 🙈
  • 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.
again: all of the retrieved pointers are internal, so do not free them after the call. borrowed pointers stay borrowed, iykyk 💜

⭐ 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. so it's a fail with no receipts 😭

🌈 SEE ALSO 🌈

👑 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.

source/version: Debian · date: June 8, 2025 · page: X509_PUBKEY_NEW(3) — okay that's the whole page bestie, love you, bye 🫶💖✨

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