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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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.
85 /* Sets the memory functions used by srp.
86 * Note: this doesn't set the memory functions used by gmp,
87 * but it is supported to have different functions for srp and gmp.
88 * Don't call this after you have already allocated srp structures.
90 void srp_set_memory_functions(
91 void *(*new_srp_alloc) (size_t),
92 void *(*new_srp_realloc) (void *, size_t),
93 void (*new_srp_free) (void *));
95 /* Out: bytes_v, len_v
97 * The caller is responsible for freeing the memory allocated for bytes_v
99 * The n_hex and g_hex parameters should be 0 unless SRP_NG_CUSTOM is used for ng_type.
100 * If provided, they must contain ASCII text of the hexidecimal notation.
102 * If bytes_s == NULL, it is filled with random data.
103 * The caller is responsible for freeing.
105 * Returns SRP_OK on success, and SRP_ERR on error.
106 * bytes_s might be in this case invalid, don't free it.
108 SRP_Result srp_create_salted_verification_key(SRP_HashAlgorithm alg,
109 SRP_NGType ng_type, const char *username_for_verifier,
110 const unsigned char *password, size_t len_password,
111 unsigned char **bytes_s, size_t *len_s,
112 unsigned char **bytes_v, size_t *len_v,
113 const char *n_hex, const char *g_hex);
115 /* Out: bytes_B, len_B.
117 * On failure, bytes_B will be set to NULL and len_B will be set to 0
119 * The n_hex and g_hex parameters should be 0 unless SRP_NG_CUSTOM is used for ng_type
121 * If bytes_b == NULL, random data is used for b.
123 * Returns pointer to SRPVerifier on success, and NULL on error.
125 struct SRPVerifier* srp_verifier_new(SRP_HashAlgorithm alg, SRP_NGType ng_type,
126 const char *username,
127 const unsigned char *bytes_s, size_t len_s,
128 const unsigned char *bytes_v, size_t len_v,
129 const unsigned char *bytes_A, size_t len_A,
130 const unsigned char *bytes_b, size_t len_b,
131 unsigned char** bytes_B, size_t *len_B,
132 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);
141 const char *srp_verifier_get_username(struct SRPVerifier *ver);
143 /* key_length may be null */
144 const unsigned char *srp_verifier_get_session_key(
145 struct SRPVerifier *ver, size_t *key_length);
147 size_t srp_verifier_get_session_key_length(struct SRPVerifier *ver);
149 /* Verifies session, on success, it writes bytes_HAMK.
150 * user_M must be exactly srp_verifier_get_session_key_length() bytes in size
152 void srp_verifier_verify_session(
153 struct SRPVerifier *ver, const unsigned char *user_M, unsigned char **bytes_HAMK);
155 /*******************************************************************************/
157 /* The n_hex and g_hex parameters should be 0 unless SRP_NG_CUSTOM is used for ng_type */
158 struct SRPUser *srp_user_new(SRP_HashAlgorithm alg, SRP_NGType ng_type,
159 const char *username, const char *username_for_verifier,
160 const unsigned char *bytes_password, size_t len_password, const char *n_hex,
163 void srp_user_delete(struct SRPUser *usr);
165 int srp_user_is_authenticated(struct SRPUser *usr);
167 const char *srp_user_get_username(struct SRPUser *usr);
169 /* key_length may be null */
170 const unsigned char *srp_user_get_session_key(struct SRPUser *usr, size_t *key_length);
172 size_t srp_user_get_session_key_length(struct SRPUser *usr);
176 /* Output: username, bytes_A, len_A.
177 * If you don't want it get written, set username to NULL.
178 * If bytes_a == NULL, random data is used for a. */
179 SRP_Result srp_user_start_authentication(struct SRPUser* usr, char **username,
180 const unsigned char *bytes_a, size_t len_a,
181 unsigned char **bytes_A, size_t* len_A);
183 /* Output: bytes_M, len_M (len_M may be null and will always be
184 * srp_user_get_session_key_length() bytes in size) */
185 void srp_user_process_challenge(struct SRPUser *usr,
186 const unsigned char *bytes_s, size_t len_s,
187 const unsigned char *bytes_B, size_t len_B,
188 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 */