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

# OSSL\_DECODER\_from\_bio(3ssl)

Routines to perform a decoding

## NAME

OSSL\_DECODER\_from\_data, OSSL\_DECODER\_from\_bio, OSSL\_DECODER\_from\_fp - Routines to perform a decoding

## SYNOPSIS

```
 #include <openssl/decoder.h>
 int OSSL_DECODER_from_bio(OSSL_DECODER_CTX *ctx, BIO *in);
 int OSSL_DECODER_from_fp(OSSL_DECODER_CTX *ctx, FILE *fp);
 int OSSL_DECODER_from_data(OSSL_DECODER_CTX *ctx, const unsigned char **pdata,
                            size_t *pdata_len);
```

Feature availability macros:

- **OSSL\_DECODER\_from\_fp()** is only available when **OPENSSL\_NO\_STDIO** is undefined.

  ## DESCRIPTION

**OSSL\_DECODER\_from\_data()** runs the decoding process for the context *ctx*, with input coming from *\*pdata*, *\*pdata\_len* bytes long.  Both *\*pdata* and *\*pdata\_len* must be non-NULL.  When **OSSL\_DECODER\_from\_data()** returns, *\*pdata* is updated to point at the location after what has been decoded, and *\*pdata\_len* to have the number of remaining bytes.

**OSSL\_DECODER\_from\_bio()** runs the decoding process for the context *ctx*, with the input coming from the **BIO** *in*.  Should it make a difference, it's recommended to have the BIO set in binary mode rather than text mode.

**OSSL\_DECODER\_from\_fp()** does the same thing as **OSSL\_DECODER\_from\_bio()**, except that the input is coming from the **FILE** *fp*.

## RETURN VALUES

**OSSL\_DECODER\_from\_bio()**, **OSSL\_DECODER\_from\_data()** and **OSSL\_DECODER\_from\_fp()** return 1 on success, or 0 on failure.

## EXAMPLES

To decode an RSA key encoded with PEM from a bio:

```
 OSSL_DECODER_CTX *dctx;
 EVP_PKEY *pkey = NULL;
 const char *format = "PEM";   /* NULL for any format */
 const char *structure = NULL; /* any structure */
 const char *keytype = "RSA";  /* NULL for any key */
 const unsigned char *pass = "my password";
 dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, format, structure,
                                      keytype,
                                      OSSL_KEYMGMT_SELECT_KEYPAIR,
                                      NULL, NULL);
 if (dctx == NULL) {
     /* error: no suitable potential decoders found */
 }
 if (pass != NULL)
     OSSL_DECODER_CTX_set_passphrase(dctx, pass, strlen(pass));
 if (OSSL_DECODER_from_bio(dctx, bio)) {
     /* pkey is created with the decoded data from the bio */
 } else {
     /* decoding failure */
 }
 OSSL_DECODER_CTX_free(dctx);
```

To decode an EC key encoded with DER from a buffer:

```
 OSSL_DECODER_CTX *dctx;
 EVP_PKEY *pkey = NULL;
 const char *format = "DER";   /* NULL for any format */
 const char *structure = NULL; /* any structure */
 const char *keytype = "EC";   /* NULL for any key */
 const unsigned char *pass = NULL
 const unsigned char *data = buffer;
 size_t datalen = sizeof(buffer);
 dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, format, structure,
                                      keytype,
                                      OSSL_KEYMGMT_SELECT_KEYPAIR
                                      | OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
                                      NULL, NULL);
 if (dctx == NULL) {
     /* error: no suitable potential decoders found */
 }
 if (pass != NULL)
     OSSL_DECODER_CTX_set_passphrase(dctx, pass, strlen(pass));
 if (OSSL_DECODER_from_data(dctx, &data, &datalen)) {
     /* pkey is created with the decoded data from the buffer */
 } else {
     /* decoding failure */
 }
 OSSL_DECODER_CTX_free(dctx);
```

## SEE ALSO

**provider**(7), **OSSL\_DECODER\_CTX**(3)

## HISTORY

The functions described here were added in OpenSSL 3.0.

## COPYRIGHT

Copyright 2020-2023 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\>.