NAME¶
SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata - set
passwd 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_userdata(SSL_CTX *ctx, void *u);
int pem_passwd_cb(char *buf, int size, int rwflag, void *userdata);
DESCRIPTION¶
SSL_CTX_set_default_passwd_cb() sets the default password callback called
when loading/storing a PEM certificate with encryption.
SSL_CTX_set_default_passwd_cb_userdata() sets a pointer to
userdata which will be provided to the password callback on invocation.
The
pem_passwd_cb(), which must be provided by the application, hands
back the password to be used during decryption. On invocation 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.
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 may depend on the
application. If only one private key is handled, it can be practical to have
pem_passwd_cb() handle the password dialog interactively. 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=1). In this
case the password dialog may ask for the same password twice for comparison in
order to catch typos, that would make decryption impossible.
Other items in PEM formatting (certificates) can also be encrypted, it is
however not usual, as certificate information is considered public.
RETURN VALUES¶
SSL_CTX_set_default_passwd_cb() and
SSL_CTX_set_default_passwd_cb_userdata() do not provide diagnostic
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¶
ssl(3),
SSL_CTX_use_certificate(3)