xref: /freebsd/crypto/openssl/doc/man3/BIO_f_base64.pod (revision a7148ab39c03abd4d1a84997c70bf96f15dd2a09)

=pod

=head1 NAME

BIO_f_base64 - base64 BIO filter

=head1 SYNOPSIS

=for openssl multiple includes

 #include <openssl/bio.h>
 #include <openssl/evp.h>

 const BIO_METHOD *BIO_f_base64(void);

=head1 DESCRIPTION

BIO_f_base64() returns the base64 BIO method. This is a filter
BIO that base64 encodes any data written through it and decodes
any data read through it.

Base64 BIOs do not support BIO_gets() or BIO_puts().

For writing, by default output is divided to lines of length 64
characters and there is a newline at the end of output.
This behavior can be changed with B<BIO_FLAGS_BASE64_NO_NL> flag.

For reading, first line should be at most 1024 bytes long including newline
unless the flag B<BIO_FLAGS_BASE64_NO_NL> is set.
Further input lines can be of any length (i.e., newlines may appear anywhere
in the input) and a newline at the end of input is not needed.

BIO_flush() on a base64 BIO that is being written through is
used to signal that no more data is to be encoded: this is used
to flush the final block through the BIO.

The flag B<BIO_FLAGS_BASE64_NO_NL> can be set with BIO_set_flags().
For writing, it causes all data to be written on one line without
newline at the end.
For reading, it removes all expectations on newlines in the input data.

=head1 NOTES

Because of the format of base64 encoding the end of the encoded
block cannot always be reliably determined.

=head1 RETURN VALUES

BIO_f_base64() returns the base64 BIO method.

=head1 EXAMPLES

Base64 encode the string "Hello World\n" and write the result
to standard output:

 BIO *bio, *b64;
 char message[] = "Hello World \n";

 b64 = BIO_new(BIO_f_base64());
 bio = BIO_new_fp(stdout, BIO_NOCLOSE);
 BIO_push(b64, bio);
 BIO_write(b64, message, strlen(message));
 BIO_flush(b64);

 BIO_free_all(b64);

Read Base64 encoded data from standard input and write the decoded
data to standard output:

 BIO *bio, *b64, *bio_out;
 char inbuf[512];
 int inlen;

 b64 = BIO_new(BIO_f_base64());
 bio = BIO_new_fp(stdin, BIO_NOCLOSE);
 bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
 BIO_push(b64, bio);
 while ((inlen = BIO_read(b64, inbuf, 512)) > 0)
     BIO_write(bio_out, inbuf, inlen);

 BIO_flush(bio_out);
 BIO_free_all(b64);

=head1 BUGS

On decoding, if the flag B<BIO_FLAGS_BASE64_NO_NL> is not set and
the first 1024 bytes of input do not include a newline character
the first two lines of input are ignored.

The ambiguity of EOF in base64 encoded data can cause additional
data following the base64 encoded block to be misinterpreted.

There should be some way of specifying a test that the BIO can perform
to reliably determine EOF (for example a MIME boundary).

=head1 COPYRIGHT

Copyright 2000-2024 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
L<https://www.openssl.org/source/license.html>.

=cut