---
name: "PEM_read_CMS"
section: "3ssl"
platform: "linux"
package: "openssl"
version: "3.6.5-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/PEM_read_CMS"
---

# PEM\_read\_CMS(3ssl)

PEM object encoding routines

## NAME

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 - PEM object encoding routines

## SYNOPSIS

```
 #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);
```

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):

```
 #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

To replace the deprecated functions listed above, 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.

In the description below, ***TYPE*** is used as a placeholder for any of the OpenSSL datatypes, such as **X509**. The macro **DECLARE\_PEM\_rw** expands to the set of declarations shown in the next four lines of the synopsis.

These routines convert between local instances of ASN1 datatypes and the PEM encoding.  For more information on the templates, see **ASN1\_ITEM**(3).  For more information on the lower-level routines used by the functions here, 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***() is similar to **PEM\_read\_*****TYPE***() but reads from the BIO *bp*.

**PEM\_write\_*****TYPE***() writes the PEM encoding of the object *a* to the file *fp*.

**PEM\_write\_bio\_*****TYPE***() similarly 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.

## 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.

**PEM\_write\_*****TYPE***() and **PEM\_write\_bio\_*****TYPE***() return 1 for success or 0 for failure.

## SEE ALSO

**PEM\_read**(3), **passphrase-encoding**(7)

## HISTORY

The functions **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()** were deprecated in OpenSSL 3.0.

## COPYRIGHT

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\>.