PEM_READ_CMS(3ossl)

📦
version 15.1 · 2 versions
, in freebsd 15.1

💖 NAME 💖

okay so this page is literally the whole PEM_read_CMS family — the OpenSSL PEM object encoding routines, no cap. Here's every single icon in the lineup:

  • DECLARE_PEM_rw
  • PEM_read_CMS, PEM_read_bio_CMS, PEM_write_CMS, PEM_write_bio_CMS
  • PEM_write_DHxparams, PEM_write_bio_DHxparams
  • PEM_read_ECPKParameters, PEM_read_bio_ECPKParameters, PEM_write_ECPKParameters, PEM_write_bio_ECPKParameters
  • PEM_read_ECPrivateKey, PEM_write_ECPrivateKey, PEM_write_bio_ECPrivateKey
  • PEM_read_EC_PUBKEY, PEM_read_bio_EC_PUBKEY, PEM_write_EC_PUBKEY, PEM_write_bio_EC_PUBKEY
  • PEM_read_NETSCAPE_CERT_SEQUENCE, PEM_read_bio_NETSCAPE_CERT_SEQUENCE, PEM_write_NETSCAPE_CERT_SEQUENCE, PEM_write_bio_NETSCAPE_CERT_SEQUENCE
  • PEM_read_PKCS8, PEM_read_bio_PKCS8, PEM_write_PKCS8, PEM_write_bio_PKCS8
  • PEM_write_PKCS8_PRIV_KEY_INFO, PEM_read_bio_PKCS8_PRIV_KEY_INFO, PEM_read_PKCS8_PRIV_KEY_INFO, PEM_write_bio_PKCS8_PRIV_KEY_INFO
  • PEM_read_SSL_SESSION, PEM_read_bio_SSL_SESSION, PEM_write_SSL_SESSION, PEM_write_bio_SSL_SESSION 🌸
  • PEM_read_X509_PUBKEY, PEM_read_bio_X509_PUBKEY, PEM_write_X509_PUBKEY, PEM_write_bio_X509_PUBKEY

(yes bestie, that's the whole squad 🫶)

✨ SYNOPSIS ✨

first up, the generic template energy:

#include <openssl/pem.h>

DECLARE_PEM_rw(name, TYPE)

TYPE *PEM_read_TYPE(FILE *fp, TYPE **a, pem_password_cb *cb, void *u);
TYPE *PEM_read_bio_TYPE(BIO *bp, TYPE **a, pem_password_cb *cb, void *u);
int PEM_write_TYPE(FILE *fp, const TYPE *a);
int PEM_write_bio_TYPE(BIO *bp, const TYPE *a);
⚠️ heads up bestie: 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). like, they're giving legacy era 🫠
#include <openssl/pem.h>

int PEM_write_DHxparams(FILE *out, const DH *dh);
int PEM_write_bio_DHxparams(BIO *out, const DH *dh);
EC_GROUP *PEM_read_ECPKParameters(FILE *fp, EC_GROUP **x, pem_password_cb *cb, void *u);
EC_GROUP *PEM_read_bio_ECPKParameters(BIO *bp, EC_GROUP **x, pem_password_cb *cb, void *u);
int PEM_write_ECPKParameters(FILE *out, const EC_GROUP *x);
int PEM_write_bio_ECPKParameters(BIO *out, const EC_GROUP *x),

EC_KEY *PEM_read_EC_PUBKEY(FILE *fp, EC_KEY **x, pem_password_cb *cb, void *u);
EC_KEY *PEM_read_bio_EC_PUBKEY(BIO *bp, EC_KEY **x, pem_password_cb *cb, void *u);
int PEM_write_EC_PUBKEY(FILE *out, const EC_KEY *x);
int PEM_write_bio_EC_PUBKEY(BIO *out, const EC_KEY *x);

EC_KEY *PEM_read_ECPrivateKey(FILE *out, EC_KEY **x, pem_password_cb *cb, void *u);
EC_KEY *PEM_read_bio_ECPrivateKey(BIO *out, EC_KEY **x, pem_password_cb *cb, void *u);
int PEM_write_ECPrivateKey(FILE *out, const EC_KEY *x, const EVP_CIPHER *enc,
                           const unsigned char *kstr, int klen,
                           pem_password_cb *cb, void *u);
int PEM_write_bio_ECPrivateKey(BIO *out, const EC_KEY *x, const EVP_CIPHER *enc,
                               const unsigned char *kstr, int klen,
                               pem_password_cb *cb, void *u);

🦋 DESCRIPTION 🦋

okay so, plot twist: to replace all those deprecated functions listed up top, applications should use the EVP_PKEY type and OSSL_DECODER_from_bio() and OSSL_ENCODER_to_bio() to read and write PEM data containing key parameters or private and public keys. that's the glow-up route ✨

in the description below, TYPE is used as a placeholder for any of the OpenSSL datatypes, such as X509. and the macro DECLARE_PEM_rw expands to the set of declarations shown in the next four lines of the synopsis. slay, generative macro 💅

these routines convert between local instances of ASN1 datatypes and the PEM encoding. want more tea on the templates? see ASN1_ITEM(3). want the lore on the lower-level routines these functions use? see PEM_read(3) 📚

  • PEM_read_TYPE() — reads a PEM-encoded object of TYPE from the file fp and returns it. the cb and u parameters are as described in pem_password_cb(3).
  • PEM_read_bio_TYPE() — same vibe as PEM_read_TYPE() but it reads from the BIO bp.
  • PEM_write_TYPE() — writes the PEM encoding of the object a to the file fp.
  • PEM_write_bio_TYPE() — same thing but writes to the BIO bp. 🎀

🙈 NOTES 🙈

these functions make no assumption regarding the pass phrase received from the password callback. it will simply be treated as a byte sequence. that's it, that's the note — bytes are bytes, no judgement 🫶

💀 RETURN VALUES 💀

  • PEM_read_TYPE() and PEM_read_bio_TYPE() return a pointer to an allocated object, which should be released by calling TYPE_free(), or NULL on error. so like… don't ghost your TYPE_free(), that's a leak 😭
  • PEM_write_TYPE() and PEM_write_bio_TYPE() return 1 for success or 0 for failure. cute and simple ⭐

🌈 SEE ALSO 🌈

PEM_read(3), passphrase-encoding(7) — go read those next, bestie, iykyk 👑

👑 HISTORY 👑

these ones were deprecated in OpenSSL 3.0, so they're officially in their flop era:

PEM_write_DHxparams(), PEM_write_bio_DHxparams(), PEM_read_ECPKParameters(), PEM_read_bio_ECPKParameters(), PEM_write_ECPKParameters(), PEM_write_bio_ECPKParameters(), PEM_read_EC_PUBKEY(), PEM_read_bio_EC_PUBKEY(), PEM_write_EC_PUBKEY(), PEM_write_bio_EC_PUBKEY(), PEM_read_ECPrivateKey(), PEM_read_bio_ECPrivateKey(), PEM_write_ECPrivateKey() and PEM_write_bio_ECPrivateKey() 🔥

Copyright 1998-2025 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 🧚 this was the OpenSSL 3ossl manual page PEM_READ_CMS(3ossl), version 3.5.6, dated 2026-04-07 — mwah, go forth and PEM responsibly 💅🍓

📦 where this page comes from