| blob | ff0773adb0ffdf134680b23517f08231940a1426 |
1 .\" $OpenBSD: SSL_CTX_set_default_passwd_cb.3,v 1.5 2018/03/21 21:20:26 schwarze Exp $
2 .\" OpenSSL 9b86974e Aug 17 15:21:33 2015 -0400
3 .\"
4 .\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>.
5 .\" Copyright (c) 2000, 2001 The OpenSSL Project. All rights reserved.
6 .\"
7 .\" Redistribution and use in source and binary forms, with or without
8 .\" modification, are permitted provided that the following conditions
9 .\" are met:
10 .\"
11 .\" 1. Redistributions of source code must retain the above copyright
12 .\" notice, this list of conditions and the following disclaimer.
13 .\"
14 .\" 2. Redistributions in binary form must reproduce the above copyright
15 .\" notice, this list of conditions and the following disclaimer in
16 .\" the documentation and/or other materials provided with the
17 .\" distribution.
18 .\"
19 .\" 3. All advertising materials mentioning features or use of this
20 .\" software must display the following acknowledgment:
21 .\" "This product includes software developed by the OpenSSL Project
22 .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
23 .\"
24 .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
25 .\" endorse or promote products derived from this software without
26 .\" prior written permission. For written permission, please contact
27 .\" openssl-core@openssl.org.
28 .\"
29 .\" 5. Products derived from this software may not be called "OpenSSL"
30 .\" nor may "OpenSSL" appear in their names without prior written
31 .\" permission of the OpenSSL Project.
32 .\"
33 .\" 6. Redistributions of any form whatsoever must retain the following
34 .\" acknowledgment:
35 .\" "This product includes software developed by the OpenSSL Project
36 .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
37 .\"
38 .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
39 .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
41 .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
42 .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
43 .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
44 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
45 .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
46 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
47 .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
48 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
49 .\" OF THE POSSIBILITY OF SUCH DAMAGE.
50 .\"
51 .Dd $Mdocdate: March 21 2018 $
52 .Dt SSL_CTX_SET_DEFAULT_PASSWD_CB 3
53 .Os
54 .Sh NAME
55 .Nm SSL_CTX_set_default_passwd_cb ,
56 .Nm SSL_CTX_set_default_passwd_cb_userdata ,
57 .Nm pem_password_cb
58 .Nd set passwd callback for encrypted PEM file handling
59 .Sh SYNOPSIS
60 .In openssl/ssl.h
61 .Ft void
62 .Fn SSL_CTX_set_default_passwd_cb "SSL_CTX *ctx" "pem_password_cb *cb"
63 .Ft void
64 .Fn SSL_CTX_set_default_passwd_cb_userdata "SSL_CTX *ctx" "void *u"
65 .In openssl/pem.h
66 .Ft typedef int
67 .Fn pem_password_cb "char *buf" "int size" "int rwflag" "void *userdata"
68 .Sh DESCRIPTION
69 .Fn SSL_CTX_set_default_passwd_cb
70 sets the default password callback called when loading/storing a PEM
71 certificate with encryption.
72 .Pp
73 .Fn SSL_CTX_set_default_passwd_cb_userdata
74 sets a pointer to userdata
75 .Fa u
76 which will be provided to the password callback on invocation.
77 .Pp
78 The
79 password callback
80 .Fa cb ,
81 which must be provided by the application,
82 hands back the password to be used during decryption.
83 On invocation a pointer to
84 .Fa userdata
85 is provided.
86 The password callback must write the password into the provided buffer
87 .Fa buf
88 which is of size
89 .Fa size .
90 The actual length of the password must be returned to the calling function.
91 .Fa rwflag
92 indicates whether the callback is used for reading/decryption
93 .Pq Fa rwflag No = 0
94 or writing/encryption
95 .Pq Fa rwflag No = 1 .
96 .Pp
97 When loading or storing private keys, a password might be supplied to protect
98 the private key.
99 The way this password can be supplied may depend on the application.
100 If only one private key is handled, it can be practical to have the
101 callback handle the password dialog interactively.
102 If several keys have to be handled, it can be practical to ask for the password
103 once, then keep it in memory and use it several times.
104 In the last case, the password could be stored into the
105 .Fa userdata
106 storage and the callback only returns the password already stored.
107 .Pp
108 When asking for the password interactively, the callback can use
109 .Fa rwflag
110 to check whether an item shall be encrypted
111 .Pq Fa rwflag No = 1 .
112 In this case the password dialog may ask for the same password twice for
113 comparison in order to catch typos which would make decryption impossible.
114 .Pp
115 Other items in PEM formatting (certificates) can also be encrypted; it is
116 however atypical, as certificate information is considered public.
117 .Sh EXAMPLES
118 The following example returns the password provided as
119 .Fa userdata
120 to the calling function.
121 The password is considered to be a
122 .Sq \e0
123 terminated string.
124 If the password does not fit into the buffer, the password is truncated.
125 .Bd -literal
126 int pem_passwd_cb(char *buf, int size, int rwflag, void *password)
127 {
128 strncpy(buf, (char *)password, size);
129 buf[size - 1] = '\e0';
130 return strlen(buf);
131 }
132 .Ed
133 .Sh SEE ALSO
134 .Xr ssl 3 ,
135 .Xr SSL_CTX_use_certificate 3
136 .Sh HISTORY
137 .Fn SSL_CTX_set_default_passwd_cb
138 appeared before SSLeay 0.8 and has been available since
139 .Ox 2.4 .
140 .Pp
141 .Fn SSL_CTX_set_default_passwd_cb_userdata
142 first appeared in OpenSSL 0.9.4 and has been available since
143 .Ox 2.6 .