xref: /freebsd/secure/lib/libcrypto/man/man3/PEM_read.3 (revision 4d3fc8b0)
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Title "PEM_READ 3"
PEM_READ 3 "2023-02-07" "1.1.1t" "OpenSSL"
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"NAME"
PEM_write, PEM_write_bio, PEM_read, PEM_read_bio, PEM_do_header, PEM_get_EVP_CIPHER_INFO \- PEM encoding routines
"SYNOPSIS"
Header "SYNOPSIS" .Vb 1 #include <openssl/pem.h> \& int PEM_write(FILE *fp, const char *name, const char *header, const unsigned char *data, long len) int PEM_write_bio(BIO *bp, const char *name, const char *header, const unsigned char *data, long len) \& 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); .Ve
"DESCRIPTION"
Header "DESCRIPTION" These functions read and write PEM-encoded objects, using the \s-1PEM\s0 type name, any additional header information, and the raw \fBdata of length len.

\s-1PEM\s0 is the term used for binary content encoding first defined in \s-1IETF RFC 1421.\s0 The content is a series of base64-encoded lines, surrounded by begin/end markers each on their own line. For example:

.Vb 4 -----BEGIN PRIVATE KEY----- MIICdg.... ... bhTQ== -----END PRIVATE KEY----- .Ve

Optional header line(s) may appear after the begin line, and their existence depends on the type of object being written or read.

\fBPEM_write() writes to the file fp, while PEM_write_bio() writes to the \s-1BIO\s0 bp. The name is the name to use in the marker, the \fBheader is the header value or \s-1NULL,\s0 and data and len specify the data and its length.

The final data buffer is typically an \s-1ASN.1\s0 object which can be decoded with the d2i function appropriate to the type name; see d2i_X509\|(3) for examples.

\fBPEM_read() reads from the file fp, while PEM_read_bio() reads from the \s-1BIO\s0 bp. Both skip any non-PEM data that precedes the start of the next \s-1PEM\s0 object. When an object is successfully retrieved, the type name from the \*(L"----BEGIN <type>-----\*(R" is returned via the name argument, any encapsulation headers are returned in header and the base64-decoded content and its length are returned via data and len respectively. The name, header and data pointers are allocated via OPENSSL_malloc() and should be freed by the caller via OPENSSL_free() when no longer needed.

\fBPEM_get_EVP_CIPHER_INFO() can be used to determine the data returned by \fBPEM_read() or PEM_read_bio() is encrypted and to retrieve the associated cipher and \s-1IV.\s0 The caller passes a pointer to structure of type \s-1EVP_CIPHER_INFO\s0 via the \fBcinfo argument and the header returned via PEM_read() or PEM_read_bio(). If the call is successful 1 is returned and the cipher and \s-1IV\s0 are stored at the address pointed to by 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 \s-1NOTES\s0 below.

\fBPEM_do_header() can then be used to decrypt the data if the header indicates encryption. The cinfo argument is a pointer to the structure initialized by the previous call to PEM_get_EVP_CIPHER_INFO(). The data and len arguments are those returned by the previous call to \fBPEM_read() or PEM_read_bio(). The cb and u arguments make it possible to override the default password prompt function as described in PEM_read_PrivateKey\|(3). On successful completion the data is decrypted in place, and len is updated to indicate the plaintext length. This function is deprecated, see \s-1NOTES\s0 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.

"RETURN VALUES"
Header "RETURN VALUES" \fBPEM_read() and PEM_read_bio() return 1 on success and 0 on failure, the latter includes the case when no more \s-1PEM\s0 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 \s-1PEM_R_NO_START_LINE\s0, which indicates that no more \s-1PEM\s0 objects were found. See ERR_peek_last_error\|(3), \s-1ERR_GET_REASON\s0\|(3).

\fBPEM_get_EVP_CIPHER_INFO() and PEM_do_header() return 1 on success, and 0 on failure. The data is likely meaningless if these functions fail.

"NOTES"
Header "NOTES" The PEM_get_EVP_CIPHER_INFO() and PEM_do_header() functions are deprecated. This is because the underlying \s-1PEM\s0 encryption format is obsolete, and should be avoided. It uses an encryption format with an OpenSSL-specific key-derivation function, which employs \s-1MD5\s0 with an iteration count of 1! Instead, private keys should be stored in PKCS#8 form, with a strong PKCS#5 v2.0 \s-1PBE.\s0 See PEM_write_PrivateKey\|(3) and d2i_PKCS8PrivateKey_bio\|(3).

\fBPEM_do_header() makes no assumption regarding the pass phrase received from the password callback. It will simply be treated as a byte sequence.

"SEE ALSO"
Header "SEE ALSO" \fBERR_peek_last_error\|(3), \s-1ERR_GET_LIB\s0\|(3), \fBd2i_PKCS8PrivateKey_bio\|(3), \fBpassphrase-encoding\|(7)
"COPYRIGHT"
Header "COPYRIGHT" Copyright 1998-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.