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SRP module documentation

Browse source 
Signed-off-by: Antoine Salon <asalon@vmware.com>

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7522)
This commit is contained in:
Antoine Salon 2018-10-25 15:43:35 -07:00 committed by Matt Caswell
parent d9720a5992
commit 495a1e5c3a
8 changed files with 466 additions and 10 deletions
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8
crypto/srp/srp_lib.c
View file

@ -44,13 +44,13 @@ static BIGNUM *srp_Calc_xy(const BIGNUM *x, const BIGNUM *y, const BIGNUM *N)
static BIGNUM *srp_Calc_k(const BIGNUM *N, const BIGNUM *g)
{
/* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
/* k = SHA1(N | PAD(g)) -- tls-srp RFC 5054 */
return srp_Calc_xy(N, g, N);
}
BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N)
{
/* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
/* u = SHA1(PAD(A) || PAD(B) ) -- tls-srp RFC 5054 */
return srp_Calc_xy(A, B, N);
}
@ -254,13 +254,13 @@ static SRP_gN knowngN[] = {
/*
* Check if G and N are known parameters. The values have been generated
* from the ietf-tls-srp draft version 8
* from the IETF RFC 5054
*/
char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N)
{
size_t i;
if ((g == NULL) || (N == NULL))
return 0;
return NULL;
for (i = 0; i < KNOWN_GN_NUMBER; i++) {
if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)

15
crypto/srp/srp_vfy.c
View file

@ -340,12 +340,13 @@ static SRP_gN *SRP_get_gN_by_id(const char *id, STACK_OF(SRP_gN) *gN_tab)
int i;
SRP_gN *gN;
if (gN_tab != NULL)
if (gN_tab != NULL) {
for (i = 0; i < sk_SRP_gN_num(gN_tab); i++) {
gN = sk_SRP_gN_value(gN_tab, i);
if (gN && (id == NULL || strcmp(gN->id, id) == 0))
return gN;
}
}
return SRP_get_default_gN(id);
}
@ -374,9 +375,13 @@ static BIGNUM *SRP_gN_place_bn(STACK_OF(SRP_gN_cache) *gN_cache, char *ch)
}
/*
* this function parses verifier file. Format is:
* string(index):base64(N):base64(g):0
* string(username):base64(v):base64(salt):int(index)
* This function parses the verifier file generated by the srp app.
* The format for each entry is:
* V base64(verifier) base64(salt) username gNid userinfo(optional)
* or
* I base64(N) base64(g)
* Note that base64 is the SRP variant of base64 encoding described
* in t_fromb64().
*/
int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file)
@ -605,7 +610,7 @@ char *SRP_create_verifier(const char *user, const char *pass, char **salt,
g_bn = g_bn_alloc;
defgNid = "*";
} else {
SRP_gN *gN = SRP_get_gN_by_id(g, NULL);
SRP_gN *gN = SRP_get_default_gN(g);
if (gN == NULL)
goto err;
N_bn = gN->N;

2
doc/man1/srp.pod
View file

@ -25,7 +25,7 @@ B<openssl srp>
=head1 DESCRIPTION
The B<srp> command is user to maintain an SRP (secure remote password)
The B<srp> command is used to maintain an SRP (secure remote password)
file.
At most one of the B<-add>, B<-modify>, B<-delete>, and B<-list> options
can be specified.

91
doc/man3/SRP_VBASE_new.pod Normal file
View file

@ -0,0 +1,91 @@
=pod
=head1 NAME
SRP_VBASE_new,
SRP_VBASE_free,
SRP_user_pwd_free,
SRP_VBASE_init,
SRP_VBASE_get1_by_user,
SRP_VBASE_get_by_user
- Functions to create and manage a stack of SRP user verifier information
=head1 SYNOPSIS
#include <openssl/srp.h>
SRP_VBASE *SRP_VBASE_new(char *seed_key);
void SRP_VBASE_free(SRP_VBASE *vb);
void SRP_user_pwd_free(SRP_user_pwd *user_pwd);
int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file);
SRP_user_pwd *SRP_VBASE_get1_by_user(SRP_VBASE *vb, char *username);
SRP_user_pwd *SRP_VBASE_get_by_user(SRP_VBASE *vb, char *username);
=head1 DESCRIPTION
The SRP_VBASE_new() function allocates a structure to store server side SRP
verifier information. If B<seed_key> is not NULL a copy is stored and used to
generate dummy parameters for users that are not found by SRP_VBASE_get1_by_user().
This allows the server to hide the fact that it doesn't have a verifier for a
particular username, as described in section 2.5.1.3 'Unknown SRP' of RFC 5054.
The seed string should contain random NUL terminated binary data (therefore
the random data should not contain NUL bytes!).
The SRP_VBASE_free() function frees up the B<vb> structure.
If B<vb> is NULL, nothing is done.
The SRP_user_pwd_free() function frees up the B<user_pwd> structure.
If B<user_pwd> is NULL, nothing is done.
The SRP_VBASE_init() function parses the information in a verifier file and
populates the B<vb> structure.
The verifier file is a text file containing multiple entries, whose format is:
flag base64(verifier) base64(salt) username gNid userinfo(optional)
where the flag can be 'V' (valid) or 'R' (revoked).
Note that the base64 encoding used here is non-standard so it is recommended
to use L<srp(1)> to generate this file.
The SRP_VBASE_get1_by_user() function returns the password info for the user
whose username matches B<username>. It replaces the deprecated
SRP_VBASE_get_by_user().
If no matching user is found but a seed_key and default gN parameters have been
set, dummy authentication information is generated from the seed_key, allowing
the server to hide the fact that it doesn't have a verifier for a particular
username. When using SRP as a TLS authentication mechanism, this will cause
the handshake to proceed normally but the first client will be rejected with
a "bad_record_mac" alert, as if the password was incorrect.
If no matching user is found and the seed_key is not set, NULL is returned.
Ownership of the returned pointer is released to the caller, it must be freed
with SRP_user_pwd_free().
=head1 RETURN VALUES
SRP_VBASE_init() returns B<SRP_NO_ERROR> (0) on success and a positive value
on failure.
The error codes are B<SRP_ERR_OPEN_FILE> if the file could not be opened,
B<SRP_ERR_VBASE_INCOMPLETE_FILE> if the file could not be parsed,
B<SRP_ERR_MEMORY> on memory allocation failure and B<SRP_ERR_VBASE_BN_LIB>
for invalid decoded parameter values.
=head1 SEE ALSO
L<srp(1)>,
L<SRP_create_verifier(3)>,
L<SSL_CTX_set_srp_password(3)>
=head1 HISTORY
These functions were first added to OpenSSL 1.0.1.
=head1 COPYRIGHT
Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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
L<https://www.openssl.org/source/license.html>.
=cut

115
doc/man3/SRP_create_verifier.pod Normal file
View file

@ -0,0 +1,115 @@
=pod
=head1 NAME
SRP_create_verifier,
SRP_create_verifier_BN,
SRP_check_known_gN_param,
SRP_get_default_gN
- SRP authentication primitives
=head1 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);
=head1 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 B<*verifier> will point to a newly allocated BIGNUM containing
the verifier and (if a salt was not provided) B<*salt> will be populated with a
newly allocated BIGNUM containing a random salt. If B<*salt> is not NULL then
the provided salt is used instead.
The caller is responsible for freeing the allocated B<*salt> and B<*verifier>
BIGNUMS (use L<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 B<N> and an SRP group id as B<g> instead to
load the appropriate gN values (see SRP_get_default_gN()).
If both B<N> and B<g> are NULL the 8192-bit SRP group parameters are used.
The caller is responsible for freeing the allocated *salt and *verifier char*
(use L<OPENSSL_free(3)>).
The SRP_check_known_gN_param() function checks that B<g> and B<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 B<id>
SRP group size.
The known ids are "1024", "1536", "2048", "3072", "4096", "6144" and "8192".
=head1 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 B<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 B<id> is not a valid group size,
or the 8192-bit group parameters if B<id> is NULL.
=head1 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_user_pwd *pwd = (SRP_user_pwd*) OPENSSL_malloc(sizeof(SRP_user_pwd));
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);
// TODO: replace with SRP_user_pwd_new()
pwd->id = OPENSSL_strdup(username);
pwd->g = gN->g;
pwd->N = gN->N;
pwd->s = salt;
pwd->v = verifier;
pwd->info = NULL;
sk_SRP_user_pwd_push(srpData->users_pwd, pwd);
=head1 SEE ALSO
L<srp(1)>,
L<BN_new(3)>,
L<OPENSSL_malloc(3)>,
L<SRP_VBASE_new(3)>
=head1 HISTORY
These functions were first added to OpenSSL 1.0.1.
=head1 COPYRIGHT
Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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
L<https://www.openssl.org/source/license.html>.
=cut

2
doc/man3/SSL_CTX_add_extra_chain_cert.pod
View file

@ -26,9 +26,11 @@ after another.
SSL_CTX_get_extra_chain_certs() retrieves the extra chain certificates
associated with B<ctx>, or the chain associated with the current certificate
of B<ctx> if the extra chain is empty.
The returned stack should not be freed by the caller.
SSL_CTX_get_extra_chain_certs_only() retrieves the extra chain certificates
associated with B<ctx>.
The returned stack should not be freed by the caller.
SSL_CTX_clear_extra_chain_certs() clears all extra chain certificates
associated with B<ctx>.

216
doc/man3/SSL_CTX_set_srp_password.pod Normal file
View file

@ -0,0 +1,216 @@
=pod
=head1 NAME
SSL_CTX_set_srp_username,
SSL_CTX_set_srp_password,
SSL_CTX_set_srp_strength,
SSL_CTX_set_srp_cb_arg,
SSL_CTX_set_srp_username_callback,
SSL_CTX_set_srp_client_pwd_callback,
SSL_CTX_set_srp_verify_param_callback,
SSL_set_srp_server_param,
SSL_set_srp_server_param_pw,
SSL_get_srp_g,
SSL_get_srp_N,
SSL_get_srp_username,
SSL_get_srp_userinfo
- SRP control operations
=head1 SYNOPSIS
#include <openssl/ssl.h>
int SSL_CTX_set_srp_username(SSL_CTX *ctx, char *name);
int SSL_CTX_set_srp_password(SSL_CTX *ctx, char *password);
int SSL_CTX_set_srp_strength(SSL_CTX *ctx, int strength);
int SSL_CTX_set_srp_cb_arg(SSL_CTX *ctx, void *arg);
int SSL_CTX_set_srp_username_callback(SSL_CTX *ctx,
int (*cb) (SSL *s, int *ad, void *arg));
int SSL_CTX_set_srp_client_pwd_callback(SSL_CTX *ctx,
char *(*cb) (SSL *s, void *arg));
int SSL_CTX_set_srp_verify_param_callback(SSL_CTX *ctx,
int (*cb) (SSL *s, void *arg));
int SSL_set_srp_server_param(SSL *s, const BIGNUM *N, const BIGNUM *g,
BIGNUM *sa, BIGNUM *v, char *info);
int SSL_set_srp_server_param_pw(SSL *s, const char *user, const char *pass,
const char *grp);
BIGNUM *SSL_get_srp_g(SSL *s);
BIGNUM *SSL_get_srp_N(SSL *s);
char *SSL_get_srp_username(SSL *s);
char *SSL_get_srp_userinfo(SSL *s);
=head1 DESCRIPTION
These functions provide access to SRP (Secure Remote Password) parameters,
an alternate authentication mechanism for TLS. SRP allows the use of user names
and passwords over unencrypted channels without revealing the password to an
eavesdropper. SRP also supplies a shared secret at the end of the authentication
sequence that can be used to generate encryption keys.
The SRP protocol, version 3 is specified in RFC 2945. SRP version 6 is described
in RFC 5054 with applications to TLS authentication.
The SSL_CTX_set_srp_username() function sets the SRP username for B<ctx>. This
should be called on the client prior to creating a connection to the server.
The length of B<name> must be shorter or equal to 255 characters.
The SSL_CTX_set_srp_password() function sets the SRP password for B<ctx>. This
may be called on the client prior to creating a connection to the server.
This overrides the effect of SSL_CTX_set_srp_client_pwd_callback().
The SSL_CTX_set_srp_strength() function sets the SRP strength for B<ctx>. This
is the minimal length of the SRP prime in bits. If not specified 1024 is used.
If not satisfied by the server key exchange the connection will be rejected.
The SSL_CTX_set_srp_cb_arg() function sets an extra parameter that will
be passed to all following callbacks as B<arg>.
The SSL_CTX_set_srp_username_callback() function sets the server side callback
that is invoked when an SRP username is found in a ClientHello.
The callback parameters are the SSL connection B<s>, a writable error flag B<ad>
and the extra argument B<arg> set by SSL_CTX_set_srp_cb_arg().
This callback should setup the server for the key exchange by calling
SSL_set_srp_server_param() with the appropriate parameters for the received
username. The username can be obtained by calling SSL_get_srp_username().
See L<SRP_VBASE_init(3)> to parse the verifier file created by L<srp(1)> or
L<SRP_create_verifier(3)> to generate it.
The callback should return B<SSL_ERROR_NONE> to proceed with the server key exchange,
B<SSL3_AL_FATAL> for a fatal error or any value < 0 for a retryable error.
In the event of a B<SSL3_AL_FATAL> the alert flag given by B<*al> will be sent
back. By default this will be B<SSL_AD_UNKOWN_PSK_IDENTITY>.
The SSL_CTX_set_srp_client_pwd_callback() function sets the client password
callback on the client.
The callback parameters are the SSL connection B<s> and the extra argument B<arg>
set by SSL_CTX_set_srp_cb_arg().
The callback will be called as part of the generation of the client secrets.
It should return the client password in text form or NULL to abort the connection.
The resulting memory will be freed by the library as part of the callback resolution.
This overrides the effect of SSL_CTX_set_srp_password().
The SSL_CTX_set_srp_verify_param_callback() sets the SRP gN parameter verification
callback on the client. This allows the client to perform custom verification when
receiving the server SRP proposed parameters.
The callback parameters are the SSL connection B<s> and the extra argument B<arg>
set by SSL_CTX_set_srp_cb_arg().
The callback should return a positive value to accept the server parameters.
Returning 0 or a negative value will abort the connection. The server parameters
can be obtained by calling SSL_get_srp_N() and SSL_get_srp_g().
Sanity checks are already performed by the library after the handshake
(B % N non zero, check against the strength parameter) and are not necessary.
If no callback is set the g and N parameters will be checked against
known RFC 5054 values.
The SSL_set_srp_server_param() function sets all SRP parameters for
the connection B<s>. B<N> and B<g> are the SRP group parameters, B<sa> is the
user salt, B<v> the password verifier and B<info> is the optional user info.
The SSL_set_srp_server_param_pw() function sets all SRP parameters for the
connection B<s> by generating a random salt and a password verifier.
B<user> is the username, B<pass> the password and B<grp> the SRP group paramters
identifier for L<SRP_get_default_gN(3)>.
The SSL_get_srp_g() function returns the SRP group generator for B<s>, or from
the underlying SSL_CTX if it is NULL.
The SSL_get_srp_N() function returns the SRP prime for B<s>, or from
the underlying SSL_CTX if it is NULL.
The SSL_get_srp_username() function returns the SRP username for B<s>, or from
the underlying SSL_CTX if it is NULL.
The SSL_get_srp_userinfo() function returns the SRP user info for B<s>, or from
the underlying SSL_CTX if it is NULL.
=head1 RETURN VALUES
All SSL_CTX_set_* functions return 1 on success and 0 on failure.
SSL_set_srp_server_param() returns 1 on success and -1 on failure.
The SSL_get_SRP_* functions return a pointer to the requested data, the memory
is owned by the library and should not be freed by the caller.
=head1 EXAMPLES
Setup SRP parameters on the client:
#include <openssl/ssl.h>
const char *username = "username";
const char *password = "password";
SSL_CTX *ctx = SSL_CTX_new(TLS_client_method());
if (!ctx)
/* Error */
if (!SSL_CTX_set_srp_username(ctx, username))
/* Error */
if (!SSL_CTX_set_srp_password(ctx, password))
/* Error */
Setup SRP server with verifier file:
#include <openssl/srp.h>
#include <openssl/ssl.h>
const char *srpvfile = "password.srpv";
int srpServerCallback(SSL *s, int *ad, void *arg)
{
SRP_VBASE *srpData = (SRP_VBASE*) arg;
char *username = SSL_get_srp_username(s);
SRP_user_pwd *user_pwd = SRP_VBASE_get1_by_user(srpData, username);
if (!user_pwd)
/* Error */
return SSL3_AL_FATAL;
if (SSL_set_srp_server_param(s, user_pwd->N, user_pwd->g,
user_pwd->s, user_pwd->v, user_pwd->info) < 0)
/* Error */
SRP_user_pwd_free(user_pwd);
return SSL_ERROR_NONE;
}
SSL_CTX *ctx = SSL_CTX_new(TLS_server_method());
if (!ctx)
/* Error */
/*
* seedKey should contain a NUL terminated sequence
* of random non NUL bytes
*/
const char *seedKey;
SRP_VBASE *srpData = SRP_VBASE_new(seedKey);
if (SRP_VBASE_init(srpData, (char*) srpvfile) != SRP_NO_ERROR)
/* Error */
SSL_CTX_set_srp_cb_arg(ctx, srpData);
SSL_CTX_set_srp_username_callback(ctx, srpServerCallback);
=head1 SEE ALSO
L<srp(1)>,
L<SRP_VBASE_new(3)>,
L<SRP_create_verifier(3)>
=head1 HISTORY
These functions were first added to OpenSSL 1.0.1.
=head1 COPYRIGHT
Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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
L<https://www.openssl.org/source/license.html>.
=cut

27
doc/man7/ssl.pod
View file

@ -375,6 +375,20 @@ Use the file path to locate trusted CA certificates.
=item void B<SSL_CTX_set_session_cache_mode>(SSL_CTX *ctx, int mode);
=item int B<SSL_CTX_set_srp_cb_arg>(SSL_CTX *ctx, void *arg);
=item int B<SSL_CTX_set_srp_client_pwd_callback>(SSL_CTX *ctx, char *(*cb)(SSL *ssl, void *arg));
=item int B<SSL_CTX_set_srp_password>(SSL_CTX *ctx, char *password);
=item int B<SSL_CTX_set_srp_strength>(SSL_CTX *ctx, int strength);
=item int B<SSL_CTX_set_srp_username>(SSL_CTX *ctx, char *name);
=item int B<SSL_CTX_set_srp_username_callback>(SSL_CTX *ctx, int (*cb)(SSL *ssl, int *ad, void *arg));
=item int B<SSL_CTX_set_srp_verify_param_callback>(SSL_CTX *ctx, int (*cb)(SSL *ssl, void *arg));
=item int B<SSL_CTX_set_ssl_version>(SSL_CTX *ctx, const SSL_METHOD *meth);
=item void B<SSL_CTX_set_timeout>(SSL_CTX *ctx, long t);
@ -582,6 +596,14 @@ fresh handle for each connection.
=item int B<SSL_get_shutdown>(const SSL *ssl);
=item BIGNUM *B<SSL_get_srp_g>(SSL *ssl);
=item BIGNUM *B<SSL_get_srp_N>(SSL *ssl);
=item char *B<SSL_get_srp_userinfo>(SSL *ssl);
=item char *B<SSL_get_srp_username>(SSL *ssl);
=item const SSL_METHOD *B<SSL_get_ssl_method>(SSL *ssl);
=item int B<SSL_get_state>(const SSL *ssl);
@ -674,6 +696,10 @@ fresh handle for each connection.
=item void B<SSL_set_shutdown>(SSL *ssl, int mode);
=item int B<SSL_set_srp_server_param>(SSL *ssl, const BIGNUM *N, const BIGNUM *g, BIGNUM *sa, BIGNUM *v, char *info);
=item int B<SSL_set_srp_server_param_pw>(SSL *ssl, const char *user, const char *pass, const char *grp);
=item int B<SSL_set_ssl_method>(SSL *ssl, const SSL_METHOD *meth);
=item void B<SSL_set_time>(SSL *ssl, long t);
@ -790,6 +816,7 @@ L<SSL_CTX_set_read_ahead(3)>,
L<SSL_CTX_set_security_level(3)>,
L<SSL_CTX_set_session_cache_mode(3)>,
L<SSL_CTX_set_session_id_context(3)>,
L<SSL_CTX_set_srp_password(3)>,
L<SSL_CTX_set_ssl_version(3)>,
L<SSL_CTX_set_timeout(3)>,
L<SSL_CTX_set_tmp_dh_callback(3)>,