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1=pod
2
3=head1 NAME
4
5SSL_CTX_set_srp_username,
6SSL_CTX_set_srp_password,
7SSL_CTX_set_srp_strength,
8SSL_CTX_set_srp_cb_arg,
9SSL_CTX_set_srp_username_callback,
10SSL_CTX_set_srp_client_pwd_callback,
11SSL_CTX_set_srp_verify_param_callback,
12SSL_set_srp_server_param,
13SSL_set_srp_server_param_pw,
14SSL_get_srp_g,
15SSL_get_srp_N,
16SSL_get_srp_username,
17SSL_get_srp_userinfo
18- SRP control operations
19
20=head1 SYNOPSIS
21
22 #include <openssl/ssl.h>
23
24The following functions have been deprecated since OpenSSL 3.0, and can be
25hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
26see L<openssl_user_macros(7)>:
27
28 int SSL_CTX_set_srp_username(SSL_CTX *ctx, char *name);
29 int SSL_CTX_set_srp_password(SSL_CTX *ctx, char *password);
30 int SSL_CTX_set_srp_strength(SSL_CTX *ctx, int strength);
31 int SSL_CTX_set_srp_cb_arg(SSL_CTX *ctx, void *arg);
32 int SSL_CTX_set_srp_username_callback(SSL_CTX *ctx,
33                                       int (*cb) (SSL *s, int *ad, void *arg));
34 int SSL_CTX_set_srp_client_pwd_callback(SSL_CTX *ctx,
35                                         char *(*cb) (SSL *s, void *arg));
36 int SSL_CTX_set_srp_verify_param_callback(SSL_CTX *ctx,
37                                           int (*cb) (SSL *s, void *arg));
38
39 int SSL_set_srp_server_param(SSL *s, const BIGNUM *N, const BIGNUM *g,
40                              BIGNUM *sa, BIGNUM *v, char *info);
41 int SSL_set_srp_server_param_pw(SSL *s, const char *user, const char *pass,
42                                 const char *grp);
43
44 BIGNUM *SSL_get_srp_g(SSL *s);
45 BIGNUM *SSL_get_srp_N(SSL *s);
46
47 char *SSL_get_srp_username(SSL *s);
48 char *SSL_get_srp_userinfo(SSL *s);
49
50=head1 DESCRIPTION
51
52All of the functions described on this page are deprecated. There are no
53available replacement functions at this time.
54
55These functions provide access to SRP (Secure Remote Password) parameters,
56an alternate authentication mechanism for TLS. SRP allows the use of usernames
57and passwords over unencrypted channels without revealing the password to an
58eavesdropper. SRP also supplies a shared secret at the end of the authentication
59sequence that can be used to generate encryption keys.
60
61The SRP protocol, version 3 is specified in RFC 2945. SRP version 6 is described
62in RFC 5054 with applications to TLS authentication.
63
64The SSL_CTX_set_srp_username() function sets the SRP username for B<ctx>. This
65should be called on the client prior to creating a connection to the server.
66The length of B<name> must be shorter or equal to 255 characters.
67
68The SSL_CTX_set_srp_password() function sets the SRP password for B<ctx>. This
69may be called on the client prior to creating a connection to the server.
70This overrides the effect of SSL_CTX_set_srp_client_pwd_callback().
71
72The SSL_CTX_set_srp_strength() function sets the SRP strength for B<ctx>. This
73is the minimal length of the SRP prime in bits. If not specified 1024 is used.
74If not satisfied by the server key exchange the connection will be rejected.
75
76The SSL_CTX_set_srp_cb_arg() function sets an extra parameter that will
77be passed to all following callbacks as B<arg>.
78
79The SSL_CTX_set_srp_username_callback() function sets the server side callback
80that is invoked when an SRP username is found in a ClientHello.
81The callback parameters are the SSL connection B<s>, a writable error flag B<ad>
82and the extra argument B<arg> set by SSL_CTX_set_srp_cb_arg().
83This callback should setup the server for the key exchange by calling
84SSL_set_srp_server_param() with the appropriate parameters for the received
85username. The username can be obtained by calling SSL_get_srp_username().
86See L<SRP_VBASE_init(3)> to parse the verifier file created by L<openssl-srp(1)> or
87L<SRP_create_verifier(3)> to generate it.
88The callback should return B<SSL_ERROR_NONE> to proceed with the server key exchange,
89B<SSL3_AL_FATAL> for a fatal error or any value < 0 for a retryable error.
90In the event of a B<SSL3_AL_FATAL> the alert flag given by B<*al> will be sent
91back. By default this will be B<SSL_AD_UNKNOWN_PSK_IDENTITY>.
92
93The SSL_CTX_set_srp_client_pwd_callback() function sets the client password
94callback on the client.
95The callback parameters are the SSL connection B<s> and the extra argument B<arg>
96set by SSL_CTX_set_srp_cb_arg().
97The callback will be called as part of the generation of the client secrets.
98It should return the client password in text form or NULL to abort the connection.
99The resulting memory will be freed by the library as part of the callback resolution.
100This overrides the effect of SSL_CTX_set_srp_password().
101
102The SSL_CTX_set_srp_verify_param_callback() sets the SRP gN parameter verification
103callback on the client. This allows the client to perform custom verification when
104receiving the server SRP proposed parameters.
105The callback parameters are the SSL connection B<s> and the extra argument B<arg>
106set by SSL_CTX_set_srp_cb_arg().
107The callback should return a positive value to accept the server parameters.
108Returning 0 or a negative value will abort the connection. The server parameters
109can be obtained by calling SSL_get_srp_N() and SSL_get_srp_g().
110Sanity checks are already performed by the library after the handshake
111(B % N non zero, check against the strength parameter) and are not necessary.
112If no callback is set the g and N parameters will be checked against
113known RFC 5054 values.
114
115The SSL_set_srp_server_param() function sets all SRP parameters for
116the connection B<s>. B<N> and B<g> are the SRP group parameters, B<sa> is the
117user salt, B<v> the password verifier and B<info> is the optional user info.
118
119The SSL_set_srp_server_param_pw() function sets all SRP parameters for the
120connection B<s> by generating a random salt and a password verifier.
121B<user> is the username, B<pass> the password and B<grp> the SRP group parameters
122identifier for L<SRP_get_default_gN(3)>.
123
124The SSL_get_srp_g() function returns the SRP group generator for B<s>, or from
125the underlying SSL_CTX if it is NULL.
126
127The SSL_get_srp_N() function returns the SRP prime for B<s>, or from
128the underlying SSL_CTX if it is NULL.
129
130The SSL_get_srp_username() function returns the SRP username for B<s>, or from
131the underlying SSL_CTX if it is NULL.
132
133The SSL_get_srp_userinfo() function returns the SRP user info for B<s>, or from
134the underlying SSL_CTX if it is NULL.
135
136=head1 RETURN VALUES
137
138All SSL_CTX_set_* functions return 1 on success and 0 on failure.
139
140SSL_set_srp_server_param() returns 1 on success and -1 on failure.
141
142The SSL_get_SRP_* functions return a pointer to the requested data, the memory
143is owned by the library and should not be freed by the caller.
144
145=head1 EXAMPLES
146
147Setup SRP parameters on the client:
148
149 #include <openssl/ssl.h>
150
151 const char *username = "username";
152 const char *password = "password";
153
154 SSL_CTX *ctx = SSL_CTX_new(TLS_client_method());
155 if (!ctx)
156     /* Error */
157 if (!SSL_CTX_set_srp_username(ctx, username))
158     /* Error */
159 if (!SSL_CTX_set_srp_password(ctx, password))
160     /* Error */
161
162Setup SRP server with verifier file:
163
164 #include <openssl/srp.h>
165 #include <openssl/ssl.h>
166
167 const char *srpvfile = "password.srpv";
168
169 int srpServerCallback(SSL *s, int *ad, void *arg)
170 {
171     SRP_VBASE *srpData = (SRP_VBASE*) arg;
172     char *username = SSL_get_srp_username(s);
173
174     SRP_user_pwd *user_pwd = SRP_VBASE_get1_by_user(srpData, username);
175     if (!user_pwd)
176         /* Error */
177         return SSL3_AL_FATAL;
178
179     if (SSL_set_srp_server_param(s, user_pwd->N, user_pwd->g,
180         user_pwd->s, user_pwd->v, user_pwd->info) < 0)
181         /* Error */
182
183     SRP_user_pwd_free(user_pwd);
184     return SSL_ERROR_NONE;
185 }
186
187 SSL_CTX *ctx = SSL_CTX_new(TLS_server_method());
188 if (!ctx)
189     /* Error */
190
191 /*
192  * seedKey should contain a NUL terminated sequence
193  * of random non NUL bytes
194  */
195 const char *seedKey;
196
197 SRP_VBASE *srpData = SRP_VBASE_new(seedKey);
198 if (SRP_VBASE_init(srpData, (char*) srpvfile) != SRP_NO_ERROR)
199    /* Error */
200
201 SSL_CTX_set_srp_cb_arg(ctx, srpData);
202 SSL_CTX_set_srp_username_callback(ctx, srpServerCallback);
203
204=head1 SEE ALSO
205
206L<ssl(7)>,
207L<openssl-srp(1)>,
208L<SRP_VBASE_new(3)>,
209L<SRP_create_verifier(3)>
210
211=head1 HISTORY
212
213These functions were added in OpenSSL 1.0.1 and deprecated in OpenSSL 3.0.
214
215=head1 COPYRIGHT
216
217Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
218
219Licensed under the Apache License 2.0 (the "License").  You may not use
220this file except in compliance with the License.  You can obtain a copy
221in the file LICENSE in the source distribution or at
222L<https://www.openssl.org/source/license.html>.
223
224=cut
225