openssl/doc/crypto/pem_read.pod

=pod

=head1 NAME

PEM_read, PEM_read_bio, PEM_do_header - low-level PEM routines

=head1 SYNOPSIS

 #include <openssl/pem.h>

 int PEM_read(FILE *fp, char **name, char **header,
              unsigned char **data, long *len);
 int PEM_read_bio(BIO *bp, char **name, char **header,
                  unsigned char **data, long *len);
 int PEM_get_EVP_CIPHER_INFO(char *header, EVP_CIPHER_INFO *cinfo);
 int PEM_do_header(EVP_CIPHER_INFO *cinfo, unsigned char *data, long *len,
                   pem_password_cb *cb, void *u);

=head1 DESCRIPTION

These functions read and decode PEM-encoded objects, returning the
PEM type B<name>, any encapsulation B<header> and the decoded
B<data> of length B<len>.

PEM_read() reads from the stdio file handle B<fp>, while PEM_read_bio() reads
from the BIO B<bio>.
Both skip any non-PEM data that precedes the start of the next PEM object.
When an object is successfuly retrieved, the type name from the "----BEGIN
<type>-----" is returned via the B<name> argument, any encapsulation headers
are returned in B<header> and the base64-decoded content and its length are
returned via B<data> and B<len> respectively.
The B<name>, B<header> and B<data> pointers are allocated via OPENSSL_malloc()
and should be freed by the caller via OPENSSL_free() when no longer needed.

PEM_get_EVP_CIPHER_INFO() can be used to determine the B<data> returned by
PEM_read() or PEM_read_bio() is encrypted and to retrieve the associated cipher
and IV.
The caller passes a pointer to structure of type B<EVP_CIPHER_INFO> via the
B<cinfo> argument and the B<header> returned via PEM_read() or PEM_read_bio().
If the call is succesful 1 is retured and the cipher and IV are stored at the
address pointed to by B<cinfo>.
When the header is malformed, or not supported or when the cipher is unknown
or some internal error happens 0 is returned.
This function is deprecated, see B<NOTES> below.

PEM_do_header() can then be used to decrypt the data if the header
indicates encryption.
The B<cinfo> argument is a pointer to the structure initialized by the previous
call to PEM_get_EVP_CIPHER_INFO().
The B<data> and B<len> arguments are those returned by the previous call to
PEM_read() or PEM_read_bio().
The B<cb> and B<u> arguments make it possible to override the default password
prompt function as described in L<pem(3)>.
On successful completion the B<data> is decrypted in place, and B<len> is
updated to indicate the plaintext length.
This function is deprecated, see B<NOTES> below.

If the data is a priori known to not be encrypted, then neither PEM_do_header()
nor PEM_get_EVP_CIPHER_INFO() need be called.

The final B<data> buffer is typically an ASN.1 object which can be decoded with
the B<d2i> function appropriate to the type B<name>.

=head1 RETURN VALUES

PEM_read() and PEM_read_bio() return 1 on success and 0 on failure, the latter
includes the case when no more PEM objects remain in the input file.
To distinguish end of file from more serious errors the caller must peek at the
error stack and check for B<PEM_R_NO_START_LINE>, which indicates that no more
PEM objects were found.  See L<ERR_peek_last_error(3)>, L<ERR_GET_REASON(3)>.

PEM_get_EVP_CIPHER_INFO() and PEM_do_header() return 1 on success, and 0 on
failure.
The B<data> is likely meaningless if these functions fail.

=head1 NOTES

The PEM_get_EVP_CIPHER_INFO() and PEM_do_header() functions are deprecated.
This is because the underlying PEM encryption format is obsolete, and should
be avoided.
It uses an encryption format with an OpenSSL-specific key-derivation function,
which employs MD5 with an iteration count of 1!
Instead, private keys should be stored in PKCS#8 form, with a strong PKCS#5
v2.0 PBE.
See L<pkcs8(1)> and L<pem(3)> and L<d2i_PKCS8PrivateKey_bio(3)>.

=head1 SEE ALSO

L<pem(3)>, L<ERR_peek_last_error(3)>, L<ERR_GET_LIB(3)>, L<pkcs8(1)>,
L<d2i_PKCS8PrivateKey_bio(3)>.