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openssl/crypto/srp/srp_vfy.c
Matt Caswell 73f0df8331 Add some sanity checks around usage of t_fromb64() 
The internal SRP function t_fromb64() converts from base64 to binary. It
does not validate that the size of the destination is sufficiently large -
that is up to the callers. In some places there was such a check, but not
in others.

Add an argument to t_fromb64() to provide the size of the destination
buffer and validate that we don't write too much data. Also add some sanity
checks to the callers where appropriate.

With thanks to Shi Lei for reporting this issue.

Reviewed-by: Richard Levitte <levitte@openssl.org>
2016-09-14 10:06:41 +01:00

678 lines
17 KiB
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/*
* Copyright 2011-2016 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
* https://www.openssl.org/source/license.html
*/
#ifndef OPENSSL_NO_SRP
# include "internal/cryptlib.h"
# include <openssl/sha.h>
# include <openssl/srp.h>
# include <openssl/evp.h>
# include <openssl/buffer.h>
# include <openssl/rand.h>
# include <openssl/txt_db.h>
# define SRP_RANDOM_SALT_LEN 20
# define MAX_LEN 2500
static char b64table[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz./";
/*
* the following two conversion routines have been inspired by code from
* Stanford
*/
/*
* Convert a base64 string into raw byte array representation.
*/
static int t_fromb64(unsigned char *a, size_t alen, const char *src)
{
char *loc;
int i, j;
int size;
while (*src && (*src == ' ' || *src == '\t' || *src == '\n'))
++src;
size = strlen(src);
if (alen > INT_MAX || size > (int)alen)
return -1;
i = 0;
while (i < size) {
loc = strchr(b64table, src[i]);
if (loc == (char *)0)
break;
else
a[i] = loc - b64table;
++i;
}
/* if nothing valid to process we have a zero length response */
if (i == 0)
return 0;
size = i;
i = size - 1;
j = size;
while (1) {
a[j] = a[i];
if (--i < 0)
break;
a[j] |= (a[i] & 3) << 6;
--j;
a[j] = (unsigned char)((a[i] & 0x3c) >> 2);
if (--i < 0)
break;
a[j] |= (a[i] & 0xf) << 4;
--j;
a[j] = (unsigned char)((a[i] & 0x30) >> 4);
if (--i < 0)
break;
a[j] |= (a[i] << 2);
a[--j] = 0;
if (--i < 0)
break;
}
while (a[j] == 0 && j <= size)
++j;
i = 0;
while (j <= size)
a[i++] = a[j++];
return i;
}
/*
* Convert a raw byte string into a null-terminated base64 ASCII string.
*/
static char *t_tob64(char *dst, const unsigned char *src, int size)
{
int c, pos = size % 3;
unsigned char b0 = 0, b1 = 0, b2 = 0, notleading = 0;
char *olddst = dst;
switch (pos) {
case 1:
b2 = src[0];
break;
case 2:
b1 = src[0];
b2 = src[1];
break;
}
while (1) {
c = (b0 & 0xfc) >> 2;
if (notleading || c != 0) {
*dst++ = b64table[c];
notleading = 1;
}
c = ((b0 & 3) << 4) | ((b1 & 0xf0) >> 4);
if (notleading || c != 0) {
*dst++ = b64table[c];
notleading = 1;
}
c = ((b1 & 0xf) << 2) | ((b2 & 0xc0) >> 6);
if (notleading || c != 0) {
*dst++ = b64table[c];
notleading = 1;
}
c = b2 & 0x3f;
if (notleading || c != 0) {
*dst++ = b64table[c];
notleading = 1;
}
if (pos >= size)
break;
else {
b0 = src[pos++];
b1 = src[pos++];
b2 = src[pos++];
}
}
*dst++ = '\0';
return olddst;
}
void SRP_user_pwd_free(SRP_user_pwd *user_pwd)
{
if (user_pwd == NULL)
return;
BN_free(user_pwd->s);
BN_clear_free(user_pwd->v);
OPENSSL_free(user_pwd->id);
OPENSSL_free(user_pwd->info);
OPENSSL_free(user_pwd);
}
static SRP_user_pwd *SRP_user_pwd_new(void)
{
SRP_user_pwd *ret = OPENSSL_malloc(sizeof(*ret));
if (ret == NULL)
return NULL;
ret->N = NULL;
ret->g = NULL;
ret->s = NULL;
ret->v = NULL;
ret->id = NULL;
ret->info = NULL;
return ret;
}
static void SRP_user_pwd_set_gN(SRP_user_pwd *vinfo, const BIGNUM *g,
const BIGNUM *N)
{
vinfo->N = N;
vinfo->g = g;
}
static int SRP_user_pwd_set_ids(SRP_user_pwd *vinfo, const char *id,
const char *info)
{
if (id != NULL && NULL == (vinfo->id = OPENSSL_strdup(id)))
return 0;
return (info == NULL || NULL != (vinfo->info = OPENSSL_strdup(info)));
}
static int SRP_user_pwd_set_sv(SRP_user_pwd *vinfo, const char *s,
const char *v)
{
unsigned char tmp[MAX_LEN];
int len;
vinfo->v = NULL;
vinfo->s = NULL;
len = t_fromb64(tmp, sizeof(tmp), v);
if (len < 0)
return 0;
if (NULL == (vinfo->v = BN_bin2bn(tmp, len, NULL)))
return 0;
len = t_fromb64(tmp, sizeof(tmp), s);
if (len < 0)
goto err;
vinfo->s = BN_bin2bn(tmp, len, NULL);
if (vinfo->s == NULL)
goto err;
return 1;
err:
BN_free(vinfo->v);
vinfo->v = NULL;
return 0;
}
static int SRP_user_pwd_set_sv_BN(SRP_user_pwd *vinfo, BIGNUM *s, BIGNUM *v)
{
vinfo->v = v;
vinfo->s = s;
return (vinfo->s != NULL && vinfo->v != NULL);
}
static SRP_user_pwd *srp_user_pwd_dup(SRP_user_pwd *src)
{
SRP_user_pwd *ret;
if (src == NULL)
return NULL;
if ((ret = SRP_user_pwd_new()) == NULL)
return NULL;
SRP_user_pwd_set_gN(ret, src->g, src->N);
if (!SRP_user_pwd_set_ids(ret, src->id, src->info)
|| !SRP_user_pwd_set_sv_BN(ret, BN_dup(src->s), BN_dup(src->v))) {
SRP_user_pwd_free(ret);
return NULL;
}
return ret;
}
SRP_VBASE *SRP_VBASE_new(char *seed_key)
{
SRP_VBASE *vb = OPENSSL_malloc(sizeof(*vb));
if (vb == NULL)
return NULL;
if ((vb->users_pwd = sk_SRP_user_pwd_new_null()) == NULL
|| (vb->gN_cache = sk_SRP_gN_cache_new_null()) == NULL) {
OPENSSL_free(vb);
return NULL;
}
vb->default_g = NULL;
vb->default_N = NULL;
vb->seed_key = NULL;
if ((seed_key != NULL) && (vb->seed_key = OPENSSL_strdup(seed_key)) == NULL) {
sk_SRP_user_pwd_free(vb->users_pwd);
sk_SRP_gN_cache_free(vb->gN_cache);
OPENSSL_free(vb);
return NULL;
}
return vb;
}
void SRP_VBASE_free(SRP_VBASE *vb)
{
if (!vb)
return;
sk_SRP_user_pwd_pop_free(vb->users_pwd, SRP_user_pwd_free);
sk_SRP_gN_cache_free(vb->gN_cache);
OPENSSL_free(vb->seed_key);
OPENSSL_free(vb);
}
static SRP_gN_cache *SRP_gN_new_init(const char *ch)
{
unsigned char tmp[MAX_LEN];
int len;
SRP_gN_cache *newgN = OPENSSL_malloc(sizeof(*newgN));
if (newgN == NULL)
return NULL;
len = t_fromb64(tmp, sizeof(tmp), ch);
if (len < 0)
goto err;
if ((newgN->b64_bn = OPENSSL_strdup(ch)) == NULL)
goto err;
if ((newgN->bn = BN_bin2bn(tmp, len, NULL)))
return newgN;
OPENSSL_free(newgN->b64_bn);
err:
OPENSSL_free(newgN);
return NULL;
}
static void SRP_gN_free(SRP_gN_cache *gN_cache)
{
if (gN_cache == NULL)
return;
OPENSSL_free(gN_cache->b64_bn);
BN_free(gN_cache->bn);
OPENSSL_free(gN_cache);
}
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)
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);
}
static BIGNUM *SRP_gN_place_bn(STACK_OF(SRP_gN_cache) *gN_cache, char *ch)
{
int i;
if (gN_cache == NULL)
return NULL;
/* search if we have already one... */
for (i = 0; i < sk_SRP_gN_cache_num(gN_cache); i++) {
SRP_gN_cache *cache = sk_SRP_gN_cache_value(gN_cache, i);
if (strcmp(cache->b64_bn, ch) == 0)
return cache->bn;
}
{ /* it is the first time that we find it */
SRP_gN_cache *newgN = SRP_gN_new_init(ch);
if (newgN) {
if (sk_SRP_gN_cache_insert(gN_cache, newgN, 0) > 0)
return newgN->bn;
SRP_gN_free(newgN);
}
}
return NULL;
}
/*
* this function parses verifier file. Format is:
* string(index):base64(N):base64(g):0
* string(username):base64(v):base64(salt):int(index)
*/
int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file)
{
int error_code;
STACK_OF(SRP_gN) *SRP_gN_tab = sk_SRP_gN_new_null();
char *last_index = NULL;
int i;
char **pp;
SRP_gN *gN = NULL;
SRP_user_pwd *user_pwd = NULL;
TXT_DB *tmpdb = NULL;
BIO *in = BIO_new(BIO_s_file());
error_code = SRP_ERR_OPEN_FILE;
if (in == NULL || BIO_read_filename(in, verifier_file) <= 0)
goto err;
error_code = SRP_ERR_VBASE_INCOMPLETE_FILE;
if ((tmpdb = TXT_DB_read(in, DB_NUMBER)) == NULL)
goto err;
error_code = SRP_ERR_MEMORY;
if (vb->seed_key) {
last_index = SRP_get_default_gN(NULL)->id;
}
for (i = 0; i < sk_OPENSSL_PSTRING_num(tmpdb->data); i++) {
pp = sk_OPENSSL_PSTRING_value(tmpdb->data, i);
if (pp[DB_srptype][0] == DB_SRP_INDEX) {
/*
* we add this couple in the internal Stack
*/
if ((gN = OPENSSL_malloc(sizeof(*gN))) == NULL)
goto err;
if ((gN->id = OPENSSL_strdup(pp[DB_srpid])) == NULL
|| (gN->N = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpverifier]))
== NULL
|| (gN->g = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpsalt]))
== NULL
|| sk_SRP_gN_insert(SRP_gN_tab, gN, 0) == 0)
goto err;
gN = NULL;
if (vb->seed_key != NULL) {
last_index = pp[DB_srpid];
}
} else if (pp[DB_srptype][0] == DB_SRP_VALID) {
/* it is a user .... */
const SRP_gN *lgN;
if ((lgN = SRP_get_gN_by_id(pp[DB_srpgN], SRP_gN_tab)) != NULL) {
error_code = SRP_ERR_MEMORY;
if ((user_pwd = SRP_user_pwd_new()) == NULL)
goto err;
SRP_user_pwd_set_gN(user_pwd, lgN->g, lgN->N);
if (!SRP_user_pwd_set_ids
(user_pwd, pp[DB_srpid], pp[DB_srpinfo]))
goto err;
error_code = SRP_ERR_VBASE_BN_LIB;
if (!SRP_user_pwd_set_sv
(user_pwd, pp[DB_srpsalt], pp[DB_srpverifier]))
goto err;
if (sk_SRP_user_pwd_insert(vb->users_pwd, user_pwd, 0) == 0)
goto err;
user_pwd = NULL; /* abandon responsibility */
}
}
}
if (last_index != NULL) {
/* this means that we want to simulate a default user */
if (((gN = SRP_get_gN_by_id(last_index, SRP_gN_tab)) == NULL)) {
error_code = SRP_ERR_VBASE_BN_LIB;
goto err;
}
vb->default_g = gN->g;
vb->default_N = gN->N;
gN = NULL;
}
error_code = SRP_NO_ERROR;
err:
/*
* there may be still some leaks to fix, if this fails, the application
* terminates most likely
*/
if (gN != NULL) {
OPENSSL_free(gN->id);
OPENSSL_free(gN);
}
SRP_user_pwd_free(user_pwd);
TXT_DB_free(tmpdb);
BIO_free_all(in);
sk_SRP_gN_free(SRP_gN_tab);
return error_code;
}
static SRP_user_pwd *find_user(SRP_VBASE *vb, char *username)
{
int i;
SRP_user_pwd *user;
if (vb == NULL)
return NULL;
for (i = 0; i < sk_SRP_user_pwd_num(vb->users_pwd); i++) {
user = sk_SRP_user_pwd_value(vb->users_pwd, i);
if (strcmp(user->id, username) == 0)
return user;
}
return NULL;
}
#if OPENSSL_API_COMPAT < 0x10100000L
/*
* DEPRECATED: use SRP_VBASE_get1_by_user instead.
* This method ignores the configured seed and fails for an unknown user.
* Ownership of the returned pointer is not released to the caller.
* In other words, caller must not free the result.
*/
SRP_user_pwd *SRP_VBASE_get_by_user(SRP_VBASE *vb, char *username)
{
return find_user(vb, username);
}
#endif
/*
* Ownership of the returned pointer is released to the caller.
* In other words, caller must free the result once done.
*/
SRP_user_pwd *SRP_VBASE_get1_by_user(SRP_VBASE *vb, char *username)
{
SRP_user_pwd *user;
unsigned char digv[SHA_DIGEST_LENGTH];
unsigned char digs[SHA_DIGEST_LENGTH];
EVP_MD_CTX *ctxt = NULL;
if (vb == NULL)
return NULL;
if ((user = find_user(vb, username)) != NULL)
return srp_user_pwd_dup(user);
if ((vb->seed_key == NULL) ||
(vb->default_g == NULL) || (vb->default_N == NULL))
return NULL;
/* if the user is unknown we set parameters as well if we have a seed_key */
if ((user = SRP_user_pwd_new()) == NULL)
return NULL;
SRP_user_pwd_set_gN(user, vb->default_g, vb->default_N);
if (!SRP_user_pwd_set_ids(user, username, NULL))
goto err;
if (RAND_bytes(digv, SHA_DIGEST_LENGTH) <= 0)
goto err;
ctxt = EVP_MD_CTX_new();
if (ctxt == NULL
|| !EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL)
|| !EVP_DigestUpdate(ctxt, vb->seed_key, strlen(vb->seed_key))
|| !EVP_DigestUpdate(ctxt, username, strlen(username))
|| !EVP_DigestFinal_ex(ctxt, digs, NULL))
goto err;
EVP_MD_CTX_free(ctxt);
ctxt = NULL;
if (SRP_user_pwd_set_sv_BN(user,
BN_bin2bn(digs, SHA_DIGEST_LENGTH, NULL),
BN_bin2bn(digv, SHA_DIGEST_LENGTH, NULL)))
return user;
err:
EVP_MD_CTX_free(ctxt);
SRP_user_pwd_free(user);
return NULL;
}
/*
* create a verifier (*salt,*verifier,g and N are in base64)
*/
char *SRP_create_verifier(const char *user, const char *pass, char **salt,
char **verifier, const char *N, const char *g)
{
int len;
char *result = NULL, *vf = NULL;
const BIGNUM *N_bn = NULL, *g_bn = NULL;
BIGNUM *N_bn_alloc = NULL, *g_bn_alloc = NULL, *s = NULL, *v = NULL;
unsigned char tmp[MAX_LEN];
unsigned char tmp2[MAX_LEN];
char *defgNid = NULL;
int vfsize = 0;
if ((user == NULL) ||
(pass == NULL) || (salt == NULL) || (verifier == NULL))
goto err;
if (N) {
if ((len = t_fromb64(tmp, sizeof(tmp), N)) <= 0)
goto err;
N_bn_alloc = BN_bin2bn(tmp, len, NULL);
N_bn = N_bn_alloc;
if ((len = t_fromb64(tmp, sizeof(tmp) ,g)) <= 0)
goto err;
g_bn_alloc = BN_bin2bn(tmp, len, NULL);
g_bn = g_bn_alloc;
defgNid = "*";
} else {
SRP_gN *gN = SRP_get_gN_by_id(g, NULL);
if (gN == NULL)
goto err;
N_bn = gN->N;
g_bn = gN->g;
defgNid = gN->id;
}
if (*salt == NULL) {
if (RAND_bytes(tmp2, SRP_RANDOM_SALT_LEN) <= 0)
goto err;
s = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);
} else {
if ((len = t_fromb64(tmp2, sizeof(tmp2), *salt)) <= 0)
goto err;
s = BN_bin2bn(tmp2, len, NULL);
}
if (!SRP_create_verifier_BN(user, pass, &s, &v, N_bn, g_bn))
goto err;
BN_bn2bin(v, tmp);
vfsize = BN_num_bytes(v) * 2;
if (((vf = OPENSSL_malloc(vfsize)) == NULL))
goto err;
t_tob64(vf, tmp, BN_num_bytes(v));
if (*salt == NULL) {
char *tmp_salt;
if ((tmp_salt = OPENSSL_malloc(SRP_RANDOM_SALT_LEN * 2)) == NULL) {
goto err;
}
t_tob64(tmp_salt, tmp2, SRP_RANDOM_SALT_LEN);
*salt = tmp_salt;
}
*verifier = vf;
vf = NULL;
result = defgNid;
err:
BN_free(N_bn_alloc);
BN_free(g_bn_alloc);
OPENSSL_clear_free(vf, vfsize);
BN_clear_free(s);
BN_clear_free(v);
return result;
}
/*
* create a verifier (*salt,*verifier,g and N are BIGNUMs). If *salt != NULL
* then the provided salt will be used. 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.
* The caller is responsible for freeing the allocated *salt and *verifier
* BIGNUMS.
*/
int SRP_create_verifier_BN(const char *user, const char *pass, BIGNUM **salt,
BIGNUM **verifier, const BIGNUM *N,
const BIGNUM *g)
{
int result = 0;
BIGNUM *x = NULL;
BN_CTX *bn_ctx = BN_CTX_new();
unsigned char tmp2[MAX_LEN];
BIGNUM *salttmp = NULL;
if ((user == NULL) ||
(pass == NULL) ||
(salt == NULL) ||
(verifier == NULL) || (N == NULL) || (g == NULL) || (bn_ctx == NULL))
goto err;
if (*salt == NULL) {
if (RAND_bytes(tmp2, SRP_RANDOM_SALT_LEN) <= 0)
goto err;
salttmp = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);
} else {
salttmp = *salt;
}
x = SRP_Calc_x(salttmp, user, pass);
*verifier = BN_new();
if (*verifier == NULL)
goto err;
if (!BN_mod_exp(*verifier, g, x, N, bn_ctx)) {
BN_clear_free(*verifier);
goto err;
}
result = 1;
*salt = salttmp;
err:
if (salt != NULL && *salt != salttmp)
BN_clear_free(salttmp);
BN_clear_free(x);
BN_CTX_free(bn_ctx);
return result;
}
#endif
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