SRP_CREATE_VERIFIER(3)

NAME
SRP_create_verifier, SRP_create_verifier_BN, SRP_check_known_gN_param, SRP_get_default_gN - SRP authentication primitives

SYNOPSIS
 #include <openssl/srp.h>

 char *SRP_create_verifier_BN(const char *user, const char *pass, BIGNUM **salt,
                              BIGNUM **verifier, const BIGNUM *N, const BIGNUM *g);
 char *SRP_create_verifier(const char *user, const char *pass, char **salt,
                           char **verifier, const char *N, const char *g);

 char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N);
 SRP_gN *SRP_get_default_gN(const char *id);

DESCRIPTION
The SRP_create_verifier_BN() function creates an SRP password verifier from the supplied parameters as defined in section 2.4 of RFC 5054. On successful exit *verifier will point to a newly allocated BIGNUM containing the verifier and (if a salt was not provided) *salt will be populated with a newly allocated BIGNUM containing a random salt. If *salt is not NULL then the provided salt is used instead. The caller is responsible for freeing the allocated *salt and *verifier BIGNUMS (use BN_free(3)).

The SRP_create_verifier() function is similar to SRP_create_verifier_BN() but all numeric parameters are in a non-standard base64 encoding originally designed for compatibility with libsrp. This is mainly present for historical compatibility and its use is discouraged. It is possible to pass NULL as N and an SRP group id as g instead to load the appropriate gN values (see SRP_get_default_gN()). If both N and g are NULL the 8192-bit SRP group parameters are used. The caller is responsible for freeing the allocated *salt and *verifier (use OPENSSL_free(3)).

The SRP_check_known_gN_param() function checks that g and N are valid SRP group parameters from RFC 5054 appendix A.

The SRP_get_default_gN() function returns the gN parameters for the RFC 5054 id SRP group size. The known ids are "1024", "1536", "2048", "3072", "4096", "6144" and "8192".

RETURN VALUES
SRP_create_verifier_BN() returns 1 on success and 0 on failure.

SRP_create_verifier() returns NULL on failure and a non-NULL value on success: "*" if N is not NULL, the selected group id otherwise. This value should not be freed.

SRP_check_known_gN_param() returns the text representation of the group id (ie. the prime bit size) or NULL if the arguments are not valid SRP group parameters. This value should not be freed.

SRP_get_default_gN() returns NULL if id is not a valid group size, or the 8192-bit group parameters if id is NULL.

EXAMPLES
Generate and store a 8192 bit password verifier (error handling omitted for clarity):

 #include <openssl/bn.h>
 #include <openssl/srp.h>

 const char *username = "username";
 const char *password = "password";

 SRP_VBASE *srpData = SRP_VBASE_new(NULL);

 SRP_gN *gN = SRP_get_default_gN("8192");

 BIGNUM *salt = NULL, *verifier = NULL;
 SRP_create_verifier_BN(username, password, &salt, &verifier, gN->N, gN->g);

 SRP_user_pwd *pwd = SRP_user_pwd_new();
 SRP_user_pwd_set1_ids(pwd, username, NULL);
 SRP_user_pwd_set0_sv(pwd, salt, verifier);
 SRP_user_pwd_set_gN(pwd, gN->g, gN->N);

 SRP_VBASE_add0_user(srpData, pwd);

SEE ALSO
openssl-srp(1), SRP_VBASE_new(3), SRP_user_pwd_new(3)

HISTORY
These functions were added in OpenSSL 1.0.1.

COPYRIGHT
Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.