1=pod
2
3=head1 NAME
4
5SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata - set passwd callback for encrypted PEM file handling
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 void SSL_CTX_set_default_passwd_cb(SSL_CTX *ctx, pem_password_cb *cb);
12 void SSL_CTX_set_default_passwd_cb_userdata(SSL_CTX *ctx, void *u);
13
14 int pem_passwd_cb(char *buf, int size, int rwflag, void *userdata);
15
16=head1 DESCRIPTION
17
18SSL_CTX_set_default_passwd_cb() sets the default password callback called
19when loading/storing a PEM certificate with encryption.
20
21SSL_CTX_set_default_passwd_cb_userdata() sets a pointer to B<userdata> which
22will be provided to the password callback on invocation.
23
24The pem_passwd_cb(), which must be provided by the application, hands back the
25password to be used during decryption. On invocation a pointer to B<userdata>
26is provided. The pem_passwd_cb must write the password into the provided buffer
27B<buf> which is of size B<size>. The actual length of the password must
28be returned to the calling function. B<rwflag> indicates whether the
29callback is used for reading/decryption (rwflag=0) or writing/encryption
30(rwflag=1).
31
32=head1 NOTES
33
34When loading or storing private keys, a password might be supplied to
35protect the private key. The way this password can be supplied may depend
36on the application. If only one private key is handled, it can be practical
37to have pem_passwd_cb() handle the password dialog interactively. If several
38keys have to be handled, it can be practical to ask for the password once,
39then keep it in memory and use it several times. In the last case, the
40password could be stored into the B<userdata> storage and the
41pem_passwd_cb() only returns the password already stored.
42
43When asking for the password interactively, pem_passwd_cb() can use
44B<rwflag> to check, whether an item shall be encrypted (rwflag=1).
45In this case the password dialog may ask for the same password twice
46for comparison in order to catch typos, that would make decryption
47impossible.
48
49Other items in PEM formatting (certificates) can also be encrypted, it is
50however not usual, as certificate information is considered public.
51
52=head1 RETURN VALUES
53
54SSL_CTX_set_default_passwd_cb() and SSL_CTX_set_default_passwd_cb_userdata()
55do not provide diagnostic information.
56
57=head1 EXAMPLES
58
59The following example returns the password provided as B<userdata> to the
60calling function. The password is considered to be a '\0' terminated
61string. If the password does not fit into the buffer, the password is
62truncated.
63
64 int pem_passwd_cb(char *buf, int size, int rwflag, void *password)
65 {
66  strncpy(buf, (char *)(password), size);
67  buf[size - 1] = '\0';
68  return(strlen(buf));
69 }
70
71=head1 SEE ALSO
72
73L<ssl(3)|ssl(3)>,
74L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)>
75
76=cut
77