pem_password_cb (3)

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NAME

pem_password_cb, PEM_read_bio_PrivateKey, PEM_read_PrivateKey, PEM_write_bio_PrivateKey, PEM_write_bio_PrivateKey_traditional, PEM_write_PrivateKey, PEM_write_bio_PKCS8PrivateKey, PEM_write_PKCS8PrivateKey, PEM_write_bio_PKCS8PrivateKey_nid, PEM_write_PKCS8PrivateKey_nid, PEM_read_bio_PUBKEY, PEM_read_PUBKEY, PEM_write_bio_PUBKEY, PEM_write_PUBKEY, PEM_read_bio_RSAPrivateKey, PEM_read_RSAPrivateKey, PEM_write_bio_RSAPrivateKey, PEM_write_RSAPrivateKey, PEM_read_bio_RSAPublicKey, PEM_read_RSAPublicKey, PEM_write_bio_RSAPublicKey, PEM_write_RSAPublicKey, PEM_read_bio_RSA_PUBKEY, PEM_read_RSA_PUBKEY, PEM_write_bio_RSA_PUBKEY, PEM_write_RSA_PUBKEY, PEM_read_bio_DSAPrivateKey, PEM_read_DSAPrivateKey, PEM_write_bio_DSAPrivateKey, PEM_write_DSAPrivateKey, PEM_read_bio_DSA_PUBKEY, PEM_read_DSA_PUBKEY, PEM_write_bio_DSA_PUBKEY, PEM_write_DSA_PUBKEY, PEM_read_bio_DSAparams, PEM_read_DSAparams, PEM_write_bio_DSAparams, PEM_write_DSAparams, PEM_read_bio_DHparams, PEM_read_DHparams, PEM_write_bio_DHparams, PEM_write_DHparams, PEM_read_bio_X509, PEM_read_X509, PEM_write_bio_X509, PEM_write_X509, PEM_read_bio_X509_AUX, PEM_read_X509_AUX, PEM_write_bio_X509_AUX, PEM_write_X509_AUX, PEM_read_bio_X509_REQ, PEM_read_X509_REQ, PEM_write_bio_X509_REQ, PEM_write_X509_REQ, PEM_write_bio_X509_REQ_NEW, PEM_write_X509_REQ_NEW, PEM_read_bio_X509_CRL, PEM_read_X509_CRL, PEM_write_bio_X509_CRL, PEM_write_X509_CRL, PEM_read_bio_PKCS7, PEM_read_PKCS7, PEM_write_bio_PKCS7, PEM_write_PKCS7 - PEM routines

SYNOPSIS

 #include <openssl/pem.h>

 typedef int pem_password_cb(char *buf, int size, int rwflag, void *u);

 EVP_PKEY *PEM_read_bio_PrivateKey(BIO *bp, EVP_PKEY **x,
                                   pem_password_cb *cb, void *u);
 EVP_PKEY *PEM_read_PrivateKey(FILE *fp, EVP_PKEY **x,
                               pem_password_cb *cb, void *u);
 int PEM_write_bio_PrivateKey(BIO *bp, EVP_PKEY *x, const EVP_CIPHER *enc,
                              unsigned char *kstr, int klen,
                              pem_password_cb *cb, void *u);
 int PEM_write_bio_PrivateKey_traditional(BIO *bp, EVP_PKEY *x,
                                          const EVP_CIPHER *enc,
                                          unsigned char *kstr, int klen,
                                          pem_password_cb *cb, void *u);
 int PEM_write_PrivateKey(FILE *fp, EVP_PKEY *x, const EVP_CIPHER *enc,
                          unsigned char *kstr, int klen,
                          pem_password_cb *cb, void *u);

 int PEM_write_bio_PKCS8PrivateKey(BIO *bp, EVP_PKEY *x, const EVP_CIPHER *enc,
                                   char *kstr, int klen,
                                   pem_password_cb *cb, void *u);
 int PEM_write_PKCS8PrivateKey(FILE *fp, EVP_PKEY *x, const EVP_CIPHER *enc,
                               char *kstr, int klen,
                               pem_password_cb *cb, void *u);
 int PEM_write_bio_PKCS8PrivateKey_nid(BIO *bp, EVP_PKEY *x, int nid,
                                       char *kstr, int klen,
                                       pem_password_cb *cb, void *u);
 int PEM_write_PKCS8PrivateKey_nid(FILE *fp, EVP_PKEY *x, int nid,
                                   char *kstr, int klen,
                                   pem_password_cb *cb, void *u);

 EVP_PKEY *PEM_read_bio_PUBKEY(BIO *bp, EVP_PKEY **x,
                               pem_password_cb *cb, void *u);
 EVP_PKEY *PEM_read_PUBKEY(FILE *fp, EVP_PKEY **x,
                           pem_password_cb *cb, void *u);
 int PEM_write_bio_PUBKEY(BIO *bp, EVP_PKEY *x);
 int PEM_write_PUBKEY(FILE *fp, EVP_PKEY *x);

 RSA *PEM_read_bio_RSAPrivateKey(BIO *bp, RSA **x,
                                 pem_password_cb *cb, void *u);
 RSA *PEM_read_RSAPrivateKey(FILE *fp, RSA **x,
                             pem_password_cb *cb, void *u);
 int PEM_write_bio_RSAPrivateKey(BIO *bp, RSA *x, const EVP_CIPHER *enc,
                                 unsigned char *kstr, int klen,
                                 pem_password_cb *cb, void *u);
 int PEM_write_RSAPrivateKey(FILE *fp, RSA *x, const EVP_CIPHER *enc,
                             unsigned char *kstr, int klen,
                             pem_password_cb *cb, void *u);

 RSA *PEM_read_bio_RSAPublicKey(BIO *bp, RSA **x,
                                pem_password_cb *cb, void *u);
 RSA *PEM_read_RSAPublicKey(FILE *fp, RSA **x,
                            pem_password_cb *cb, void *u);
 int PEM_write_bio_RSAPublicKey(BIO *bp, RSA *x);
 int PEM_write_RSAPublicKey(FILE *fp, RSA *x);

 RSA *PEM_read_bio_RSA_PUBKEY(BIO *bp, RSA **x,
                              pem_password_cb *cb, void *u);
 RSA *PEM_read_RSA_PUBKEY(FILE *fp, RSA **x,
                          pem_password_cb *cb, void *u);
 int PEM_write_bio_RSA_PUBKEY(BIO *bp, RSA *x);
 int PEM_write_RSA_PUBKEY(FILE *fp, RSA *x);

 DSA *PEM_read_bio_DSAPrivateKey(BIO *bp, DSA **x,
                                 pem_password_cb *cb, void *u);
 DSA *PEM_read_DSAPrivateKey(FILE *fp, DSA **x,
                             pem_password_cb *cb, void *u);
 int PEM_write_bio_DSAPrivateKey(BIO *bp, DSA *x, const EVP_CIPHER *enc,
                                 unsigned char *kstr, int klen,
                                 pem_password_cb *cb, void *u);
 int PEM_write_DSAPrivateKey(FILE *fp, DSA *x, const EVP_CIPHER *enc,
                             unsigned char *kstr, int klen,
                             pem_password_cb *cb, void *u);

 DSA *PEM_read_bio_DSA_PUBKEY(BIO *bp, DSA **x,
                              pem_password_cb *cb, void *u);
 DSA *PEM_read_DSA_PUBKEY(FILE *fp, DSA **x,
                          pem_password_cb *cb, void *u);
 int PEM_write_bio_DSA_PUBKEY(BIO *bp, DSA *x);
 int PEM_write_DSA_PUBKEY(FILE *fp, DSA *x);

 DSA *PEM_read_bio_DSAparams(BIO *bp, DSA **x, pem_password_cb *cb, void *u);
 DSA *PEM_read_DSAparams(FILE *fp, DSA **x, pem_password_cb *cb, void *u);
 int PEM_write_bio_DSAparams(BIO *bp, DSA *x);
 int PEM_write_DSAparams(FILE *fp, DSA *x);

 DH *PEM_read_bio_DHparams(BIO *bp, DH **x, pem_password_cb *cb, void *u);
 DH *PEM_read_DHparams(FILE *fp, DH **x, pem_password_cb *cb, void *u);
 int PEM_write_bio_DHparams(BIO *bp, DH *x);
 int PEM_write_DHparams(FILE *fp, DH *x);

 X509 *PEM_read_bio_X509(BIO *bp, X509 **x, pem_password_cb *cb, void *u);
 X509 *PEM_read_X509(FILE *fp, X509 **x, pem_password_cb *cb, void *u);
 int PEM_write_bio_X509(BIO *bp, X509 *x);
 int PEM_write_X509(FILE *fp, X509 *x);

 X509 *PEM_read_bio_X509_AUX(BIO *bp, X509 **x, pem_password_cb *cb, void *u);
 X509 *PEM_read_X509_AUX(FILE *fp, X509 **x, pem_password_cb *cb, void *u);
 int PEM_write_bio_X509_AUX(BIO *bp, X509 *x);
 int PEM_write_X509_AUX(FILE *fp, X509 *x);

 X509_REQ *PEM_read_bio_X509_REQ(BIO *bp, X509_REQ **x,
                                 pem_password_cb *cb, void *u);
 X509_REQ *PEM_read_X509_REQ(FILE *fp, X509_REQ **x,
                             pem_password_cb *cb, void *u);
 int PEM_write_bio_X509_REQ(BIO *bp, X509_REQ *x);
 int PEM_write_X509_REQ(FILE *fp, X509_REQ *x);
 int PEM_write_bio_X509_REQ_NEW(BIO *bp, X509_REQ *x);
 int PEM_write_X509_REQ_NEW(FILE *fp, X509_REQ *x);

 X509_CRL *PEM_read_bio_X509_CRL(BIO *bp, X509_CRL **x,
                                 pem_password_cb *cb, void *u);
 X509_CRL *PEM_read_X509_CRL(FILE *fp, X509_CRL **x,
                             pem_password_cb *cb, void *u);
 int PEM_write_bio_X509_CRL(BIO *bp, X509_CRL *x);
 int PEM_write_X509_CRL(FILE *fp, X509_CRL *x);

 PKCS7 *PEM_read_bio_PKCS7(BIO *bp, PKCS7 **x, pem_password_cb *cb, void *u);
 PKCS7 *PEM_read_PKCS7(FILE *fp, PKCS7 **x, pem_password_cb *cb, void *u);
 int PEM_write_bio_PKCS7(BIO *bp, PKCS7 *x);
 int PEM_write_PKCS7(FILE *fp, PKCS7 *x);

DESCRIPTION

The functions read or write structures in format. In this sense format is simply base64 encoded data surrounded by header lines.

For more details about the meaning of arguments see the

section.

Each operation has four functions associated with it. For clarity the term "foobar functions" will be used to collectively refer to the PEM_read_bio_foobar(), PEM_read_foobar(), PEM_write_bio_foobar() and PEM_write_foobar() functions.

The PrivateKey functions read or write a private key in

format using an structure. The write routines use PKCS#8 private key format and are equivalent to PEM_write_bio_PKCS8PrivateKey().The read functions transparently handle traditional and PKCS#8 format encrypted and unencrypted keys.

PEM_write_bio_PrivateKey_traditional() writes out a private key in legacy ``traditional'' format.

PEM_write_bio_PKCS8PrivateKey() and PEM_write_PKCS8PrivateKey() write a private key in an

structure in PKCS#8 EncryptedPrivateKeyInfo format using PKCS#5 v2.0 password based encryption algorithms. The cipher argument specifies the encryption algorithm to use: unlike some other routines the encryption is applied at the PKCS#8 level and not in the headers. If cipher is then no encryption is used and a PKCS#8 PrivateKeyInfo structure is used instead.

PEM_write_bio_PKCS8PrivateKey_nid() and PEM_write_PKCS8PrivateKey_nid() also write out a private key as a PKCS#8 EncryptedPrivateKeyInfo however it uses PKCS#5 v1.5 or PKCS#12 encryption algorithms instead. The algorithm to use is specified in the nid parameter and should be the

of the corresponding (see section).

The

functions process a public key using an structure. The public key is encoded as a SubjectPublicKeyInfo structure.

The RSAPrivateKey functions process an

private key using an structure. The write routines uses traditional format. The read routines handles the same formats as the PrivateKey functions but an error occurs if the private key is not

The RSAPublicKey functions process an

public key using an structure. The public key is encoded using a PKCS#1 RSAPublicKey structure.

The

functions also process an public key using an structure. However the public key is encoded using a SubjectPublicKeyInfo structure and an error occurs if the public key is not

The DSAPrivateKey functions process a

private key using a structure. The write routines uses traditional format. The read routines handles the same formats as the PrivateKey functions but an error occurs if the private key is not

The

functions process a public key using a structure. The public key is encoded using a SubjectPublicKeyInfo structure and an error occurs if the public key is not

The DSAparams functions process

parameters using a structure. The parameters are encoded using a Dss-Parms structure as defined in

The DHparams functions process

parameters using a structure. The parameters are encoded using a PKCS#3 DHparameter structure.

The X509 functions process an X509 certificate using an X509 structure. They will also process a trusted X509 certificate but any trust settings are discarded.

The X509_AUX functions process a trusted X509 certificate using an X509 structure.

The X509_REQ and X509_REQ_NEW functions process a PKCS#10 certificate request using an X509_REQ structure. The X509_REQ write functions use

in the header whereas the X509_REQ_NEW functions use (as required by some CAs). The X509_REQ read functions will handle either form so there are no X509_REQ_NEW read functions.

The X509_CRL functions process an X509

using an X509_CRL structure.

The

functions process a PKCS#7 ContentInfo using a structure.

PEM FUNCTION ARGUMENTS

The functions have many common arguments.

The bp

parameter (if present) specifies the to read from or write to.

The fp

parameter (if present) specifies the pointer to read from or write to.

The

read functions all take an argument **x and return a * pointer. Where is whatever structure the function uses. If x is then the parameter is ignored. If x is not but *x is then the structure returned will be written to *x. If neither x nor *x is then an attempt is made to reuse the structure at *x (but see and sections). Irrespective of the value of x a pointer to the structure is always returned (or if an error occurred).

The

functions which write private keys take an enc parameter which specifies the encryption algorithm to use, encryption is done at the level. If this parameter is set to then the private key is written in unencrypted form.

The cb argument is the callback to use when querying for the pass phrase used for encrypted

structures (normally only private keys).

For the

write routines if the kstr parameter is not then klen bytes at kstr are used as the passphrase and cb is ignored.

If the cb parameters is set to

and the u parameter is not then the u parameter is interpreted as a null terminated string to use as the passphrase. If both cb and u are then the default callback routine is used which will typically prompt for the passphrase on the current terminal with echoing turned off.

The default passphrase callback is sometimes inappropriate (for example in a

application) so an alternative can be supplied. The callback routine has the following form:

 int cb(char *buf, int size, int rwflag, void *u);

buf is the buffer to write the passphrase to. size is the maximum length of the passphrase (i.e. the size of buf). rwflag is a flag which is set to 0 when reading and 1 when writing. A typical routine will ask the user to verify the passphrase (for example by prompting for it twice) if rwflag is 1. The u parameter has the same value as the u parameter passed to the

routine. It allows arbitrary data to be passed to the callback by the application (for example a window handle in a application). The callback must return the number of characters in the passphrase or 0 if an error occurred.

EXAMPLES

Although the routines take several arguments in almost all applications most of them are set to 0 or

Read a certificate in

format from a

 X509 *x;
 x = PEM_read_bio_X509(bp, NULL, 0, NULL);
 if (x == NULL) {
     /* Error */
 }

Alternative method:

 X509 *x = NULL;
 if (!PEM_read_bio_X509(bp, &x, 0, NULL)) {
     /* Error */
 }

Write a certificate to a

 if (!PEM_write_bio_X509(bp, x)) {
     /* Error */
 }

Write a private key (using traditional format) to a

using triple encryption, the pass phrase is prompted for:

 if (!PEM_write_bio_PrivateKey(bp, key, EVP_des_ede3_cbc(), NULL, 0, 0, NULL)) {
     /* Error */
 }

Write a private key (using PKCS#8 format) to a

using triple encryption, using the pass phrase ``hello'':

 if (!PEM_write_bio_PKCS8PrivateKey(bp, key, EVP_des_ede3_cbc(), NULL, 0, 0, "hello")) {
     /* Error */
 }

Read a private key from a

using a pass phrase callback:

 key = PEM_read_bio_PrivateKey(bp, NULL, pass_cb, "My Private Key");
 if (key == NULL) {
     /* Error */
 }

Skeleton pass phrase callback:

 int pass_cb(char *buf, int size, int rwflag, void *u)
 {
     int len;
     char *tmp;

     /* We'd probably do something else if 'rwflag' is 1 */
     printf("Enter pass phrase for \"%s\"\n", (char *)u);

     /* get pass phrase, length 'len' into 'tmp' */
     tmp = "hello";
     len = strlen(tmp);
     if (len <= 0)
         return 0;

     if (len > size)
         len = size;
     memcpy(buf, tmp, len);
     return len;
 }

NOTES

The old PrivateKey write routines are retained for compatibility. New applications should write private keys using the PEM_write_bio_PKCS8PrivateKey() or PEM_write_PKCS8PrivateKey() routines because they are more secure (they use an iteration count of 2048 whereas the traditional routines use a count of 1) unless compatibility with older versions of OpenSSL is important.

The PrivateKey read routines can be used in all applications because they handle all formats transparently.

A frequent cause of problems is attempting to use the

routines like this:

 X509 *x;
 PEM_read_bio_X509(bp, &x, 0, NULL);

this is a bug because an attempt will be made to reuse the data at x which is an uninitialised pointer.

PEM ENCRYPTION FORMAT

These old PrivateKey routines use a non standard technique for encryption.

The private key (or other data) takes the following form:

 -----BEGIN RSA PRIVATE KEY-----
 Proc-Type: 4,ENCRYPTED
 DEK-Info: DES-EDE3-CBC,3F17F5316E2BAC89

 ...base64 encoded data...
 -----END RSA PRIVATE KEY-----

The line beginning with Proc-Type contains the version and the protection on the encapsulated data. The line beginning DEK-Info contains two comma separated values: the encryption algorithm name as used by EVP_get_cipherbyname() and an initialization vector used by the cipher encoded as a set of hexadecimal digits. After those two lines is the base64-encoded encrypted data.

The encryption key is derived using EVP_BytesToKey(). The cipher's initialization vector is passed to EVP_BytesToKey() as the salt parameter. Internally,

bytes of the salt are used (regardless of the size of the initialization vector). The user's password is passed to EVP_BytesToKey() using the data and datal parameters. Finally, the library uses an iteration count of 1 for EVP_BytesToKey().

The key derived by EVP_BytesToKey() along with the original initialization vector is then used to decrypt the encrypted data. The iv produced by EVP_BytesToKey() is not utilized or needed, and

should be passed to the function.

The pseudo code to derive the key would look similar to:

 EVP_CIPHER* cipher = EVP_des_ede3_cbc();
 EVP_MD* md = EVP_md5();

 unsigned int nkey = EVP_CIPHER_key_length(cipher);
 unsigned int niv = EVP_CIPHER_iv_length(cipher);
 unsigned char key[nkey];
 unsigned char iv[niv];

 memcpy(iv, HexToBin("3F17F5316E2BAC89"), niv);
 rc = EVP_BytesToKey(cipher, md, iv /*salt*/, pword, plen, 1, key, NULL /*iv*/);
 if (rc != nkey) {
     /* Error */
 }

 /* On success, use key and iv to initialize the cipher */

BUGS

The read routines in some versions of OpenSSL will not correctly reuse an existing structure. Therefore the following:

 PEM_read_bio_X509(bp, &x, 0, NULL);

where x already contains a valid certificate, may not work, whereas:

 X509_free(x);
 x = PEM_read_bio_X509(bp, NULL, 0, NULL);

is guaranteed to work.

RETURN CODES

The read routines return either a pointer to the structure read or if an error occurred.

The write routines return 1 for success or 0 for failure.

HISTORY

The old Netscape certificate sequences were no longer documented in OpenSSL 1.1; applications should use the standard instead as they will be formally deprecated in a future releases.

SEE ALSO

EVP_EncryptInit(3), EVP_BytesToKey(3)

COPYRIGHT

Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the ``License''). You may not use this file except in compliance with the License. You can obtain a copy in the file

in the source distribution or at <www.openssl.org/source/license.html>.