SSL_CTX_set_default_passwd_cb(3)SSL_CTX_set_default_passwd_cb(3)NAME
SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata -
Set password callback for encrypted PEM file handling
SYNOPSIS
#include <openssl/ssl.h>
void SSL_CTX_set_default_passwd_cb(
SSL_CTX *ctx,
pem_password_cb *cb ); void SSL_CTX_set_default_passwd_cb_user‐
data(
SSL_CTX *ctx,
void *u ); int pem_passwd_cb(
char *buf,
int size,
int rwflag,
void *userdata );
DESCRIPTION
The SSL_CTX_set_default_passwd_cb() function sets the default password
callback called when loading or storing a PEM certificate with encryp‐
tion.
The SSL_CTX_set_default_passwd_cb_userdata() function sets a pointer to
userdata which will be provided to the password callback on invocation.
The pem_passwd_cb() function, which must be provided by the applica‐
tion, hands back the password to be used during decryption. On invoca‐
tion a pointer to userdata is provided. The pem_passwd_cb() must write
the password into the provided buffer buf which is of size size. The
actual length of the password must be returned to the calling function.
The <literal role="strong">rwflag indicates whether the callback is
used for reading/decryption (rwflag=0) or writing/encryption
(rwflag=1).
NOTES
When loading or storing private keys, a password might be supplied to
protect the private key. The way this password can be supplied might
depend on the application. If only one private key is handled, it can
be practical to have pem_passwd_cb() handle the password dialog inter‐
actively. If several keys have to be handled, it can be practical to
ask for the password once, then keep it in memory and use it several
times. In the last case, the password could be stored into the userdata
storage and the pem_passwd_cb() only returns the password already
stored.
When asking for the password interactively, pem_passwd_cb() can use
rwflag to check whether an item shall be encrypted (rwflag=3D1). In
this case the password dialog may ask for the same password twice for
comparison in order to catch typos that would make decryption impossi‐
ble.
Other items in PEM formatting (certificates) can also be encrypted. It
is not usual, as certificate information is considered public.
RETURN VALUES
The SSL_CTX_set_default_passwd_cb() and
SSL_CTX_set_default_passwd_cb_userdata() functions do not provide diag‐
nostic information.
EXAMPLES
The following example returns the password provided as userdata to the
calling function. The password is considered to be a '\0' terminated
string. If the password does not fit into the buffer, the password is
truncated.
int pem_passwd_cb(char *buf, int size, int rwflag, void *password)
{
strncpy(buf, (char *)(password), size);
buf[size - 1] = '\0';
return(strlen(buf));
}
SEE ALSO
Functions: ssl(3), SSL_CTX_use_certificate(3)SSL_CTX_set_default_passwd_cb(3)