2 * Secure Remote Password 6a implementation
3 * https://github.com/est31/csrp-gmp
5 * The MIT License (MIT)
7 * Copyright (c) 2010, 2013 Tom Cocagne, 2015 est31 <MTest31@outlook.com>
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10 * this software and associated documentation files (the "Software"), to deal in
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20 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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31 * Purpose: This is a direct implementation of the Secure Remote Password
32 * Protocol version 6a as described by
33 * http://srp.stanford.edu/design.html
35 * Author: tom.cocagne@gmail.com (Tom Cocagne)
37 * Dependencies: LibGMP
39 * Usage: Refer to test_srp.c for a demonstration
42 * This library allows multiple combinations of hashing algorithms and
43 * prime number constants. For authentication to succeed, the hash and
44 * prime number constants must match between
45 * srp_create_salted_verification_key(), srp_user_new(),
46 * and srp_verifier_new(). A recommended approach is to determine the
47 * desired level of security for an application and globally define the
48 * hash and prime number constants to the predetermined values.
50 * As one might suspect, more bits means more security. As one might also
51 * suspect, more bits also means more processing time. The test_srp.c
52 * program can be easily modified to profile various combinations of
53 * hash & prime number pairings.
87 /* Sets the memory functions used by srp.
88 * Note: this doesn't set the memory functions used by gmp,
89 * but it is supported to have different functions for srp and gmp.
90 * Don't call this after you have already allocated srp structures.
92 void srp_set_memory_functions(
93 void *(*new_srp_alloc) (size_t),
94 void *(*new_srp_realloc) (void *, size_t),
95 void (*new_srp_free) (void *));
97 /* Out: bytes_v, len_v
99 * The caller is responsible for freeing the memory allocated for bytes_v
101 * The n_hex and g_hex parameters should be 0 unless SRP_NG_CUSTOM is used for ng_type.
102 * If provided, they must contain ASCII text of the hexidecimal notation.
104 * If bytes_s == NULL, it is filled with random data. The caller is responsible for freeing.
106 * Returns SRP_OK on success, and SRP_ERR on error.
107 * bytes_s might be in this case invalid, don't free it.
109 SRP_Result srp_create_salted_verification_key( SRP_HashAlgorithm alg,
110 SRP_NGType ng_type, const char *username_for_verifier,
111 const unsigned char *password, size_t len_password,
112 unsigned char **bytes_s, size_t *len_s,
113 unsigned char **bytes_v, size_t *len_v,
114 const char * n_hex, const char *g_hex );
116 /* Out: bytes_B, len_B.
118 * On failure, bytes_B will be set to NULL and len_B will be set to 0
120 * The n_hex and g_hex parameters should be 0 unless SRP_NG_CUSTOM is used for ng_type
122 * If bytes_b == NULL, random data is used for b.
124 * Returns pointer to SRPVerifier on success, and NULL on error.
126 struct SRPVerifier* srp_verifier_new(SRP_HashAlgorithm alg, SRP_NGType ng_type,
127 const char *username,
128 const unsigned char *bytes_s, size_t len_s,
129 const unsigned char *bytes_v, size_t len_v,
130 const unsigned char *bytes_A, size_t len_A,
131 const unsigned char *bytes_b, size_t len_b,
132 unsigned char** bytes_B, size_t *len_B,
133 const char* n_hex, const char* g_hex);
136 void srp_verifier_delete( struct SRPVerifier* ver );
138 // srp_verifier_verify_session must have been called before
139 int srp_verifier_is_authenticated( struct SRPVerifier* ver );
142 const char * srp_verifier_get_username( struct SRPVerifier* ver );
144 /* key_length may be null */
145 const unsigned char* srp_verifier_get_session_key( struct SRPVerifier* ver,
146 size_t *key_length );
149 size_t srp_verifier_get_session_key_length(struct SRPVerifier* ver);
152 /* Verifies session, on success, it writes bytes_HAMK.
153 * user_M must be exactly srp_verifier_get_session_key_length() bytes in size
155 void srp_verifier_verify_session( struct SRPVerifier* ver,
156 const unsigned char* user_M, unsigned char** bytes_HAMK );
158 /*******************************************************************************/
160 /* The n_hex and g_hex parameters should be 0 unless SRP_NG_CUSTOM is used for ng_type */
161 struct SRPUser *srp_user_new(SRP_HashAlgorithm alg, SRP_NGType ng_type,
162 const char *username, const char *username_for_verifier,
163 const unsigned char *bytes_password, size_t len_password,
164 const char *n_hex, const char *g_hex);
166 void srp_user_delete(struct SRPUser * usr);
168 int srp_user_is_authenticated(struct SRPUser * usr);
171 const char* srp_user_get_username(struct SRPUser * usr);
173 /* key_length may be null */
174 const unsigned char* srp_user_get_session_key(struct SRPUser* usr, size_t* key_length);
176 size_t srp_user_get_session_key_length(struct SRPUser* usr);
178 /* Output: username, bytes_A, len_A. If you don't want it get written, set username to NULL.
179 * If bytes_a == NULL, random data is used for a. */
180 SRP_Result srp_user_start_authentication(struct SRPUser* usr, char** username,
181 const unsigned char* bytes_a, size_t len_a,
182 unsigned char** bytes_A, size_t* len_A);
184 /* Output: bytes_M, len_M (len_M may be null and will always be
185 * srp_user_get_session_key_length() bytes in size) */
186 void srp_user_process_challenge(struct SRPUser *usr,
187 const unsigned char *bytes_s, size_t len_s,
188 const unsigned char *bytes_B, size_t len_B,
189 unsigned char **bytes_M, size_t *len_M);
191 /* bytes_HAMK must be exactly srp_user_get_session_key_length() bytes in size */
192 void srp_user_verify_session(struct SRPUser* usr, const unsigned char* bytes_HAMK);
194 #endif /* Include Guard */