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.\" $NetBSD: openssl_pem.3,v 1.1 2003/07/24 14:16:52 itojun Exp $
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.\" ======================================================================
.\"
.IX Title "pem 3"
.TH pem 3 "0.9.7b" "2002-01-04" "OpenSSL"
.UC
.SH "NAME"
\&\s-1PEM\s0 \- \s-1PEM\s0 routines
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/pem.h>
.Ve
.Vb 2
\& EVP_PKEY *PEM_read_bio_PrivateKey(BIO *bp, EVP_PKEY **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& EVP_PKEY *PEM_read_PrivateKey(FILE *fp, EVP_PKEY **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& 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);
.Ve
.Vb 3
\& int PEM_write_PrivateKey(FILE *fp, EVP_PKEY *x, const EVP_CIPHER *enc,
\& unsigned char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_bio_PKCS8PrivateKey(BIO *bp, EVP_PKEY *x, const EVP_CIPHER *enc,
\& char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_PKCS8PrivateKey(FILE *fp, EVP_PKEY *x, const EVP_CIPHER *enc,
\& char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_bio_PKCS8PrivateKey_nid(BIO *bp, EVP_PKEY *x, int nid,
\& char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_PKCS8PrivateKey_nid(FILE *fp, EVP_PKEY *x, int nid,
\& char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& EVP_PKEY *PEM_read_bio_PUBKEY(BIO *bp, EVP_PKEY **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& EVP_PKEY *PEM_read_PUBKEY(FILE *fp, EVP_PKEY **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& int PEM_write_bio_PUBKEY(BIO *bp, EVP_PKEY *x);
\& int PEM_write_PUBKEY(FILE *fp, EVP_PKEY *x);
.Ve
.Vb 2
\& RSA *PEM_read_bio_RSAPrivateKey(BIO *bp, RSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& RSA *PEM_read_RSAPrivateKey(FILE *fp, RSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_bio_RSAPrivateKey(BIO *bp, RSA *x, const EVP_CIPHER *enc,
\& unsigned char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_RSAPrivateKey(FILE *fp, RSA *x, const EVP_CIPHER *enc,
\& unsigned char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& RSA *PEM_read_bio_RSAPublicKey(BIO *bp, RSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& RSA *PEM_read_RSAPublicKey(FILE *fp, RSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_RSAPublicKey(BIO *bp, RSA *x);
.Ve
.Vb 1
\& int PEM_write_RSAPublicKey(FILE *fp, RSA *x);
.Ve
.Vb 2
\& RSA *PEM_read_bio_RSA_PUBKEY(BIO *bp, RSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& RSA *PEM_read_RSA_PUBKEY(FILE *fp, RSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_RSA_PUBKEY(BIO *bp, RSA *x);
.Ve
.Vb 1
\& int PEM_write_RSA_PUBKEY(FILE *fp, RSA *x);
.Ve
.Vb 2
\& DSA *PEM_read_bio_DSAPrivateKey(BIO *bp, DSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& DSA *PEM_read_DSAPrivateKey(FILE *fp, DSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_bio_DSAPrivateKey(BIO *bp, DSA *x, const EVP_CIPHER *enc,
\& unsigned char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& int PEM_write_DSAPrivateKey(FILE *fp, DSA *x, const EVP_CIPHER *enc,
\& unsigned char *kstr, int klen,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& DSA *PEM_read_bio_DSA_PUBKEY(BIO *bp, DSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& DSA *PEM_read_DSA_PUBKEY(FILE *fp, DSA **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_DSA_PUBKEY(BIO *bp, DSA *x);
.Ve
.Vb 1
\& int PEM_write_DSA_PUBKEY(FILE *fp, DSA *x);
.Ve
.Vb 1
\& DSA *PEM_read_bio_DSAparams(BIO *bp, DSA **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& DSA *PEM_read_DSAparams(FILE *fp, DSA **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_DSAparams(BIO *bp, DSA *x);
.Ve
.Vb 1
\& int PEM_write_DSAparams(FILE *fp, DSA *x);
.Ve
.Vb 1
\& DH *PEM_read_bio_DHparams(BIO *bp, DH **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& DH *PEM_read_DHparams(FILE *fp, DH **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_DHparams(BIO *bp, DH *x);
.Ve
.Vb 1
\& int PEM_write_DHparams(FILE *fp, DH *x);
.Ve
.Vb 1
\& X509 *PEM_read_bio_X509(BIO *bp, X509 **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& X509 *PEM_read_X509(FILE *fp, X509 **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_X509(BIO *bp, X509 *x);
.Ve
.Vb 1
\& int PEM_write_X509(FILE *fp, X509 *x);
.Ve
.Vb 1
\& X509 *PEM_read_bio_X509_AUX(BIO *bp, X509 **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& X509 *PEM_read_X509_AUX(FILE *fp, X509 **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_X509_AUX(BIO *bp, X509 *x);
.Ve
.Vb 1
\& int PEM_write_X509_AUX(FILE *fp, X509 *x);
.Ve
.Vb 2
\& X509_REQ *PEM_read_bio_X509_REQ(BIO *bp, X509_REQ **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 2
\& X509_REQ *PEM_read_X509_REQ(FILE *fp, X509_REQ **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_X509_REQ(BIO *bp, X509_REQ *x);
.Ve
.Vb 1
\& int PEM_write_X509_REQ(FILE *fp, X509_REQ *x);
.Ve
.Vb 1
\& int PEM_write_bio_X509_REQ_NEW(BIO *bp, X509_REQ *x);
.Ve
.Vb 1
\& int PEM_write_X509_REQ_NEW(FILE *fp, X509_REQ *x);
.Ve
.Vb 6
\& 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);
.Ve
.Vb 1
\& PKCS7 *PEM_read_bio_PKCS7(BIO *bp, PKCS7 **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& PKCS7 *PEM_read_PKCS7(FILE *fp, PKCS7 **x, pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_PKCS7(BIO *bp, PKCS7 *x);
.Ve
.Vb 1
\& int PEM_write_PKCS7(FILE *fp, PKCS7 *x);
.Ve
.Vb 3
\& NETSCAPE_CERT_SEQUENCE *PEM_read_bio_NETSCAPE_CERT_SEQUENCE(BIO *bp,
\& NETSCAPE_CERT_SEQUENCE **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 3
\& NETSCAPE_CERT_SEQUENCE *PEM_read_NETSCAPE_CERT_SEQUENCE(FILE *fp,
\& NETSCAPE_CERT_SEQUENCE **x,
\& pem_password_cb *cb, void *u);
.Ve
.Vb 1
\& int PEM_write_bio_NETSCAPE_CERT_SEQUENCE(BIO *bp, NETSCAPE_CERT_SEQUENCE *x);
.Ve
.Vb 1
\& int PEM_write_NETSCAPE_CERT_SEQUENCE(FILE *fp, NETSCAPE_CERT_SEQUENCE *x);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1PEM\s0 functions read or write structures in \s-1PEM\s0 format. In
this sense \s-1PEM\s0 format is simply base64 encoded data surrounded
by header lines.
.PP
For more details about the meaning of arguments see the
\&\fB\s-1PEM\s0 \s-1FUNCTION\s0 \s-1ARGUMENTS\s0\fR section.
.PP
Each operation has four functions associated with it. For
clarity the term "\fBfoobar\fR functions" will be used to collectively
refer to the \fIPEM_read_bio_foobar()\fR, \fIPEM_read_foobar()\fR,
\&\fIPEM_write_bio_foobar()\fR and \fIPEM_write_foobar()\fR functions.
.PP
The \fBPrivateKey\fR functions read or write a private key in
\&\s-1PEM\s0 format using an \s-1EVP_PKEY\s0 structure. The write routines use
\&\*(L"traditional\*(R" private key format and can handle both \s-1RSA\s0 and \s-1DSA\s0
private keys. The read functions can additionally transparently
handle PKCS#8 format encrypted and unencrypted keys too.
.PP
\&\fIPEM_write_bio_PKCS8PrivateKey()\fR and \fIPEM_write_PKCS8PrivateKey()\fR
write a private key in an \s-1EVP_PKEY\s0 structure in PKCS#8
EncryptedPrivateKeyInfo format using PKCS#5 v2.0 password based encryption
algorithms. The \fBcipher\fR argument specifies the encryption algoritm to
use: unlike all other \s-1PEM\s0 routines the encryption is applied at the
PKCS#8 level and not in the \s-1PEM\s0 headers. If \fBcipher\fR is \s-1NULL\s0 then no
encryption is used and a PKCS#8 PrivateKeyInfo structure is used instead.
.PP
\&\fIPEM_write_bio_PKCS8PrivateKey_nid()\fR and \fIPEM_write_PKCS8PrivateKey_nid()\fR
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 \fBnid\fR parameter and should be the \s-1NID\s0 of the
corresponding \s-1OBJECT\s0 \s-1IDENTIFIER\s0 (see \s-1NOTES\s0 section).
.PP
The \fB\s-1PUBKEY\s0\fR functions process a public key using an \s-1EVP_PKEY\s0
structure. The public key is encoded as a SubjectPublicKeyInfo
structure.
.PP
The \fBRSAPrivateKey\fR functions process an \s-1RSA\s0 private key using an
\&\s-1RSA\s0 structure. It handles the same formats as the \fBPrivateKey\fR
functions but an error occurs if the private key is not \s-1RSA\s0.
.PP
The \fBRSAPublicKey\fR functions process an \s-1RSA\s0 public key using an
\&\s-1RSA\s0 structure. The public key is encoded using a PKCS#1 RSAPublicKey
structure.
.PP
The \fB\s-1RSA_PUBKEY\s0\fR functions also process an \s-1RSA\s0 public key using
an \s-1RSA\s0 structure. However the public key is encoded using a
SubjectPublicKeyInfo structure and an error occurs if the public
key is not \s-1RSA\s0.
.PP
The \fBDSAPrivateKey\fR functions process a \s-1DSA\s0 private key using a
\&\s-1DSA\s0 structure. It handles the same formats as the \fBPrivateKey\fR
functions but an error occurs if the private key is not \s-1DSA\s0.
.PP
The \fB\s-1DSA_PUBKEY\s0\fR functions process a \s-1DSA\s0 public key using
a \s-1DSA\s0 structure. The public key is encoded using a
SubjectPublicKeyInfo structure and an error occurs if the public
key is not \s-1DSA\s0.
.PP
The \fBDSAparams\fR functions process \s-1DSA\s0 parameters using a \s-1DSA\s0
structure. The parameters are encoded using a foobar structure.
.PP
The \fBDHparams\fR functions process \s-1DH\s0 parameters using a \s-1DH\s0
structure. The parameters are encoded using a PKCS#3 DHparameter
structure.
.PP
The \fBX509\fR functions process an X509 certificate using an X509
structure. They will also process a trusted X509 certificate but
any trust settings are discarded.
.PP
The \fBX509_AUX\fR functions process a trusted X509 certificate using
an X509 structure.
.PP
The \fBX509_REQ\fR and \fBX509_REQ_NEW\fR functions process a PKCS#10
certificate request using an X509_REQ structure. The \fBX509_REQ\fR
write functions use \fB\s-1CERTIFICATE\s0 \s-1REQUEST\s0\fR in the header whereas
the \fBX509_REQ_NEW\fR functions use \fB\s-1NEW\s0 \s-1CERTIFICATE\s0 \s-1REQUEST\s0\fR
(as required by some CAs). The \fBX509_REQ\fR read functions will
handle either form so there are no \fBX509_REQ_NEW\fR read functions.
.PP
The \fBX509_CRL\fR functions process an X509 \s-1CRL\s0 using an X509_CRL
structure.
.PP
The \fB\s-1PKCS7\s0\fR functions process a PKCS#7 ContentInfo using a \s-1PKCS7\s0
structure.
.PP
The \fB\s-1NETSCAPE_CERT_SEQUENCE\s0\fR functions process a Netscape Certificate
Sequence using a \s-1NETSCAPE_CERT_SEQUENCE\s0 structure.
.SH "PEM FUNCTION ARGUMENTS"
.IX Header "PEM FUNCTION ARGUMENTS"
The \s-1PEM\s0 functions have many common arguments.
.PP
The \fBbp\fR \s-1BIO\s0 parameter (if present) specifies the \s-1BIO\s0 to read from
or write to.
.PP
The \fBfp\fR \s-1FILE\s0 parameter (if present) specifies the \s-1FILE\s0 pointer to
read from or write to.
.PP
The \s-1PEM\s0 read functions all take an argument \fB\s-1TYPE\s0 **x\fR and return
a \fB\s-1TYPE\s0 *\fR pointer. Where \fB\s-1TYPE\s0\fR is whatever structure the function
uses. If \fBx\fR is \s-1NULL\s0 then the parameter is ignored. If \fBx\fR is not
\&\s-1NULL\s0 but \fB*x\fR is \s-1NULL\s0 then the structure returned will be written
to \fB*x\fR. If neither \fBx\fR nor \fB*x\fR is \s-1NULL\s0 then an attempt is made
to reuse the structure at \fB*x\fR (but see \s-1BUGS\s0 and \s-1EXAMPLES\s0 sections).
Irrespective of the value of \fBx\fR a pointer to the structure is always
returned (or \s-1NULL\s0 if an error occurred).
.PP
The \s-1PEM\s0 functions which write private keys take an \fBenc\fR parameter
which specifies the encryption algorithm to use, encryption is done
at the \s-1PEM\s0 level. If this parameter is set to \s-1NULL\s0 then the private
key is written in unencrypted form.
.PP
The \fBcb\fR argument is the callback to use when querying for the pass
phrase used for encrypted \s-1PEM\s0 structures (normally only private keys).
.PP
For the \s-1PEM\s0 write routines if the \fBkstr\fR parameter is not \s-1NULL\s0 then
\&\fBklen\fR bytes at \fBkstr\fR are used as the passphrase and \fBcb\fR is
ignored.
.PP
If the \fBcb\fR parameters is set to \s-1NULL\s0 and the \fBu\fR parameter is not
\&\s-1NULL\s0 then the \fBu\fR parameter is interpreted as a null terminated string
to use as the passphrase. If both \fBcb\fR and \fBu\fR are \s-1NULL\s0 then the
default callback routine is used which will typically prompt for the
passphrase on the current terminal with echoing turned off.
.PP
The default passphrase callback is sometimes inappropriate (for example
in a \s-1GUI\s0 application) so an alternative can be supplied. The callback
routine has the following form:
.PP
.Vb 1
\& int cb(char *buf, int size, int rwflag, void *u);
.Ve
\&\fBbuf\fR is the buffer to write the passphrase to. \fBsize\fR is the maximum
length of the passphrase (i.e. the size of buf). \fBrwflag\fR 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 \fBrwflag\fR is 1. The \fBu\fR parameter has the same
value as the \fBu\fR parameter passed to the \s-1PEM\s0 routine. It allows
arbitrary data to be passed to the callback by the application
(for example a window handle in a \s-1GUI\s0 application). The callback
\&\fBmust\fR return the number of characters in the passphrase or 0 if
an error occurred.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Although the \s-1PEM\s0 routines take several arguments in almost all applications
most of them are set to 0 or \s-1NULL\s0.
.PP
Read a certificate in \s-1PEM\s0 format from a \s-1BIO:\s0
.PP
.Vb 6
\& X509 *x;
\& x = PEM_read_bio(bp, NULL, 0, NULL);
\& if (x == NULL)
\& {
\& /* Error */
\& }
.Ve
Alternative method:
.PP
.Vb 5
\& X509 *x = NULL;
\& if (!PEM_read_bio_X509(bp, &x, 0, NULL))
\& {
\& /* Error */
\& }
.Ve
Write a certificate to a \s-1BIO:\s0
.PP
.Vb 4
\& if (!PEM_write_bio_X509(bp, x))
\& {
\& /* Error */
\& }
.Ve
Write an unencrypted private key to a \s-1FILE\s0 pointer:
.PP
.Vb 4
\& if (!PEM_write_PrivateKey(fp, key, NULL, NULL, 0, 0, NULL))
\& {
\& /* Error */
\& }
.Ve
Write a private key (using traditional format) to a \s-1BIO\s0 using
triple \s-1DES\s0 encryption, the pass phrase is prompted for:
.PP
.Vb 4
\& if (!PEM_write_bio_PrivateKey(bp, key, EVP_des_ede3_cbc(), NULL, 0, 0, NULL))
\& {
\& /* Error */
\& }
.Ve
Write a private key (using PKCS#8 format) to a \s-1BIO\s0 using triple
\&\s-1DES\s0 encryption, using the pass phrase \*(L"hello\*(R":
.PP
.Vb 4
\& if (!PEM_write_bio_PKCS8PrivateKey(bp, key, EVP_des_ede3_cbc(), NULL, 0, 0, "hello"))
\& {
\& /* Error */
\& }
.Ve
Read a private key from a \s-1BIO\s0 using the pass phrase \*(L"hello\*(R":
.PP
.Vb 5
\& key = PEM_read_bio_PrivateKey(bp, NULL, 0, "hello");
\& if (key == NULL)
\& {
\& /* Error */
\& }
.Ve
Read a private key from a \s-1BIO\s0 using a pass phrase callback:
.PP
.Vb 5
\& key = PEM_read_bio_PrivateKey(bp, NULL, pass_cb, "My Private Key");
\& if (key == NULL)
\& {
\& /* Error */
\& }
.Ve
Skeleton pass phrase callback:
.PP
.Vb 6
\& 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 \e"%s\e"\en", u);
.Ve
.Vb 3
\& /* get pass phrase, length 'len' into 'tmp' */
\& tmp = "hello";
\& len = strlen(tmp);
.Ve
.Vb 6
\& if (len <= 0) return 0;
\& /* if too long, truncate */
\& if (len > size) len = size;
\& memcpy(buf, tmp, len);
\& return len;
\& }
.Ve
.SH "NOTES"
.IX Header "NOTES"
The old \fBPrivateKey\fR write routines are retained for compatibility.
New applications should write private keys using the
\&\fIPEM_write_bio_PKCS8PrivateKey()\fR or \fIPEM_write_PKCS8PrivateKey()\fR 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.
.PP
The \fBPrivateKey\fR read routines can be used in all applications because
they handle all formats transparently.
.PP
A frequent cause of problems is attempting to use the \s-1PEM\s0 routines like
this:
.PP
.Vb 2
\& X509 *x;
\& PEM_read_bio_X509(bp, &x, 0, NULL);
.Ve
this is a bug because an attempt will be made to reuse the data at \fBx\fR
which is an uninitialised pointer.
.SH "PEM ENCRYPTION FORMAT"
.IX Header "PEM ENCRYPTION FORMAT"
This old \fBPrivateKey\fR routines use a non standard technique for encryption.
.PP
The private key (or other data) takes the following form:
.PP
.Vb 3
\& -----BEGIN RSA PRIVATE KEY-----
\& Proc-Type: 4,ENCRYPTED
\& DEK-Info: DES-EDE3-CBC,3F17F5316E2BAC89
.Ve
.Vb 2
\& ...base64 encoded data...
\& -----END RSA PRIVATE KEY-----
.Ve
The line beginning DEK-Info contains two comma separated pieces of information:
the encryption algorithm name as used by \fIEVP_get_cipherbyname()\fR and an 8
byte \fBsalt\fR encoded as a set of hexadecimal digits.
.PP
After this is the base64 encoded encrypted data.
.PP
The encryption key is determined using \fIEVP_bytestokey()\fR, using \fBsalt\fR and an
iteration count of 1. The \s-1IV\s0 used is the value of \fBsalt\fR and *not* the \s-1IV\s0
returned by \fIEVP_bytestokey()\fR.
.SH "BUGS"
.IX Header "BUGS"
The \s-1PEM\s0 read routines in some versions of OpenSSL will not correctly reuse
an existing structure. Therefore the following:
.PP
.Vb 1
\& PEM_read_bio(bp, &x, 0, NULL);
.Ve
where \fBx\fR already contains a valid certificate, may not work, whereas:
.PP
.Vb 2
\& X509_free(x);
\& x = PEM_read_bio(bp, NULL, 0, NULL);
.Ve
is guaranteed to work.
.SH "RETURN CODES"
.IX Header "RETURN CODES"
The read routines return either a pointer to the structure read or \s-1NULL\s0
is an error occurred.
.PP
The write routines return 1 for success or 0 for failure.
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