1/*
2 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright 2005 Nokia. All rights reserved.
4 *
5 * Licensed under the Apache License 2.0 (the "License").  You may not use
6 * this file except in compliance with the License.  You can obtain a copy
7 * in the file LICENSE in the source distribution or at
8 * https://www.openssl.org/source/license.html
9 */
10
11/*
12 * This file is to enable backwards compatibility for the SRP features of
13 * s_client, s_server and ciphers. All of those features are deprecated and will
14 * eventually disappear. In the meantime, to continue to support them, we
15 * need to access deprecated SRP APIs.
16 */
17#define OPENSSL_SUPPRESS_DEPRECATED
18
19#include <openssl/bn.h>
20#include <openssl/bio.h>
21#include <openssl/ssl.h>
22#include <openssl/srp.h>
23#include "apps_ui.h"
24#include "apps.h"
25#include "s_apps.h"
26
27static int srp_Verify_N_and_g(const BIGNUM *N, const BIGNUM *g)
28{
29    BN_CTX *bn_ctx = BN_CTX_new();
30    BIGNUM *p = BN_new();
31    BIGNUM *r = BN_new();
32    int ret =
33        g != NULL && N != NULL && bn_ctx != NULL && BN_is_odd(N) &&
34        BN_check_prime(N, bn_ctx, NULL) == 1 &&
35        p != NULL && BN_rshift1(p, N) &&
36        /* p = (N-1)/2 */
37        BN_check_prime(p, bn_ctx, NULL) == 1 &&
38        r != NULL &&
39        /* verify g^((N-1)/2) == -1 (mod N) */
40        BN_mod_exp(r, g, p, N, bn_ctx) &&
41        BN_add_word(r, 1) && BN_cmp(r, N) == 0;
42
43    BN_free(r);
44    BN_free(p);
45    BN_CTX_free(bn_ctx);
46    return ret;
47}
48
49/*-
50 * This callback is used here for two purposes:
51 * - extended debugging
52 * - making some primality tests for unknown groups
53 * The callback is only called for a non default group.
54 *
55 * An application does not need the call back at all if
56 * only the standard groups are used.  In real life situations,
57 * client and server already share well known groups,
58 * thus there is no need to verify them.
59 * Furthermore, in case that a server actually proposes a group that
60 * is not one of those defined in RFC 5054, it is more appropriate
61 * to add the group to a static list and then compare since
62 * primality tests are rather cpu consuming.
63 */
64
65static int ssl_srp_verify_param_cb(SSL *s, void *arg)
66{
67    SRP_ARG *srp_arg = (SRP_ARG *)arg;
68    BIGNUM *N = NULL, *g = NULL;
69
70    if (((N = SSL_get_srp_N(s)) == NULL) || ((g = SSL_get_srp_g(s)) == NULL))
71        return 0;
72    if (srp_arg->debug || srp_arg->msg || srp_arg->amp == 1) {
73        BIO_printf(bio_err, "SRP parameters:\n");
74        BIO_printf(bio_err, "\tN=");
75        BN_print(bio_err, N);
76        BIO_printf(bio_err, "\n\tg=");
77        BN_print(bio_err, g);
78        BIO_printf(bio_err, "\n");
79    }
80
81    if (SRP_check_known_gN_param(g, N))
82        return 1;
83
84    if (srp_arg->amp == 1) {
85        if (srp_arg->debug)
86            BIO_printf(bio_err,
87                       "SRP param N and g are not known params, going to check deeper.\n");
88
89        /*
90         * The srp_moregroups is a real debugging feature. Implementors
91         * should rather add the value to the known ones. The minimal size
92         * has already been tested.
93         */
94        if (BN_num_bits(g) <= BN_BITS && srp_Verify_N_and_g(N, g))
95            return 1;
96    }
97    BIO_printf(bio_err, "SRP param N and g rejected.\n");
98    return 0;
99}
100
101#define PWD_STRLEN 1024
102
103static char *ssl_give_srp_client_pwd_cb(SSL *s, void *arg)
104{
105    SRP_ARG *srp_arg = (SRP_ARG *)arg;
106    char *pass = app_malloc(PWD_STRLEN + 1, "SRP password buffer");
107    PW_CB_DATA cb_tmp;
108    int l;
109
110    cb_tmp.password = (char *)srp_arg->srppassin;
111    cb_tmp.prompt_info = "SRP user";
112    if ((l = password_callback(pass, PWD_STRLEN, 0, &cb_tmp)) < 0) {
113        BIO_printf(bio_err, "Can't read Password\n");
114        OPENSSL_free(pass);
115        return NULL;
116    }
117    *(pass + l) = '\0';
118
119    return pass;
120}
121
122int set_up_srp_arg(SSL_CTX *ctx, SRP_ARG *srp_arg, int srp_lateuser, int c_msg,
123                   int c_debug)
124{
125    if (!srp_lateuser && !SSL_CTX_set_srp_username(ctx, srp_arg->srplogin)) {
126        BIO_printf(bio_err, "Unable to set SRP username\n");
127        return 0;
128    }
129    srp_arg->msg = c_msg;
130    srp_arg->debug = c_debug;
131    SSL_CTX_set_srp_cb_arg(ctx, &srp_arg);
132    SSL_CTX_set_srp_client_pwd_callback(ctx, ssl_give_srp_client_pwd_cb);
133    SSL_CTX_set_srp_strength(ctx, srp_arg->strength);
134    if (c_msg || c_debug || srp_arg->amp == 0)
135        SSL_CTX_set_srp_verify_param_callback(ctx, ssl_srp_verify_param_cb);
136
137    return 1;
138}
139
140static char *dummy_srp(SSL *ssl, void *arg)
141{
142    return "";
143}
144
145void set_up_dummy_srp(SSL_CTX *ctx)
146{
147        SSL_CTX_set_srp_client_pwd_callback(ctx, dummy_srp);
148}
149
150/*
151 * This callback pretends to require some asynchronous logic in order to
152 * obtain a verifier. When the callback is called for a new connection we
153 * return with a negative value. This will provoke the accept etc to return
154 * with an LOOKUP_X509. The main logic of the reinvokes the suspended call
155 * (which would normally occur after a worker has finished) and we set the
156 * user parameters.
157 */
158static int ssl_srp_server_param_cb(SSL *s, int *ad, void *arg)
159{
160    srpsrvparm *p = (srpsrvparm *) arg;
161    int ret = SSL3_AL_FATAL;
162
163    if (p->login == NULL && p->user == NULL) {
164        p->login = SSL_get_srp_username(s);
165        BIO_printf(bio_err, "SRP username = \"%s\"\n", p->login);
166        return -1;
167    }
168
169    if (p->user == NULL) {
170        BIO_printf(bio_err, "User %s doesn't exist\n", p->login);
171        goto err;
172    }
173
174    if (SSL_set_srp_server_param
175        (s, p->user->N, p->user->g, p->user->s, p->user->v,
176         p->user->info) < 0) {
177        *ad = SSL_AD_INTERNAL_ERROR;
178        goto err;
179    }
180    BIO_printf(bio_err,
181               "SRP parameters set: username = \"%s\" info=\"%s\" \n",
182               p->login, p->user->info);
183    ret = SSL_ERROR_NONE;
184
185 err:
186    SRP_user_pwd_free(p->user);
187    p->user = NULL;
188    p->login = NULL;
189    return ret;
190}
191
192int set_up_srp_verifier_file(SSL_CTX *ctx, srpsrvparm *srp_callback_parm,
193                             char *srpuserseed, char *srp_verifier_file)
194{
195    int ret;
196
197    srp_callback_parm->vb = SRP_VBASE_new(srpuserseed);
198    srp_callback_parm->user = NULL;
199    srp_callback_parm->login = NULL;
200
201    if (srp_callback_parm->vb == NULL) {
202        BIO_printf(bio_err, "Failed to initialize SRP verifier file \n");
203        return 0;
204    }
205    if ((ret =
206            SRP_VBASE_init(srp_callback_parm->vb,
207                           srp_verifier_file)) != SRP_NO_ERROR) {
208        BIO_printf(bio_err,
209                    "Cannot initialize SRP verifier file \"%s\":ret=%d\n",
210                    srp_verifier_file, ret);
211        return 0;
212    }
213    SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, verify_callback);
214    SSL_CTX_set_srp_cb_arg(ctx, &srp_callback_parm);
215    SSL_CTX_set_srp_username_callback(ctx, ssl_srp_server_param_cb);
216
217    return 1;
218}
219
220void lookup_srp_user(srpsrvparm *srp_callback_parm, BIO *bio_s_out)
221{
222    SRP_user_pwd_free(srp_callback_parm->user);
223    srp_callback_parm->user = SRP_VBASE_get1_by_user(srp_callback_parm->vb,
224                                                     srp_callback_parm->login);
225
226    if (srp_callback_parm->user != NULL)
227        BIO_printf(bio_s_out, "LOOKUP done %s\n",
228                    srp_callback_parm->user->info);
229    else
230        BIO_printf(bio_s_out, "LOOKUP not successful\n");
231}
232