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openssh/kex-names.c

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/* $OpenBSD: kex-names.c,v 1.1 2024/05/17 00:32:32 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#ifdef WITH_OPENSSL
#include <openssl/crypto.h>
#include <openssl/evp.h>
#endif
#include "kex.h"
#include "log.h"
#include "match.h"
#include "digest.h"
#include "misc.h"
#include "ssherr.h"
#include "xmalloc.h"
struct kexalg {
char *name;
u_int type;
int ec_nid;
int hash_alg;
};
static const struct kexalg kexalgs[] = {
#ifdef WITH_OPENSSL
{ KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
{ KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
{ KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
{ KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
{ KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
{ KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
#ifdef HAVE_EVP_SHA256
{ KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
#endif /* HAVE_EVP_SHA256 */
#ifdef OPENSSL_HAS_ECC
{ KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
{ KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
SSH_DIGEST_SHA384 },
# ifdef OPENSSL_HAS_NISTP521
{ KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
SSH_DIGEST_SHA512 },
# endif /* OPENSSL_HAS_NISTP521 */
#endif /* OPENSSL_HAS_ECC */
#endif /* WITH_OPENSSL */
#if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)
{ KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
{ KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
#ifdef USE_SNTRUP761X25519
{ KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
SSH_DIGEST_SHA512 },
#endif
#endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
{ NULL, 0, -1, -1},
};
char *
kex_alg_list(char sep)
{
char *ret = NULL, *tmp;
size_t nlen, rlen = 0;
const struct kexalg *k;
for (k = kexalgs; k->name != NULL; k++) {
if (ret != NULL)
ret[rlen++] = sep;
nlen = strlen(k->name);
if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
free(ret);
return NULL;
}
ret = tmp;
memcpy(ret + rlen, k->name, nlen + 1);
rlen += nlen;
}
return ret;
}
static const struct kexalg *
kex_alg_by_name(const char *name)
{
const struct kexalg *k;
for (k = kexalgs; k->name != NULL; k++) {
if (strcmp(k->name, name) == 0)
return k;
}
return NULL;
}
int
kex_name_valid(const char *name)
{
return kex_alg_by_name(name) != NULL;
}
u_int
kex_type_from_name(const char *name)
{
const struct kexalg *k;
if ((k = kex_alg_by_name(name)) == NULL)
return 0;
return k->type;
}
int
kex_hash_from_name(const char *name)
{
const struct kexalg *k;
if ((k = kex_alg_by_name(name)) == NULL)
return -1;
return k->hash_alg;
}
int
kex_nid_from_name(const char *name)
{
const struct kexalg *k;
if ((k = kex_alg_by_name(name)) == NULL)
return -1;
return k->ec_nid;
}
/* Validate KEX method name list */
int
kex_names_valid(const char *names)
{
char *s, *cp, *p;
if (names == NULL || strcmp(names, "") == 0)
return 0;
if ((s = cp = strdup(names)) == NULL)
return 0;
for ((p = strsep(&cp, ",")); p && *p != '\0';
(p = strsep(&cp, ","))) {
if (kex_alg_by_name(p) == NULL) {
error("Unsupported KEX algorithm \"%.100s\"", p);
free(s);
return 0;
}
}
debug3("kex names ok: [%s]", names);
free(s);
return 1;
}
/* returns non-zero if proposal contains any algorithm from algs */
int
kex_has_any_alg(const char *proposal, const char *algs)
{
char *cp;
if ((cp = match_list(proposal, algs, NULL)) == NULL)
return 0;
free(cp);
return 1;
}
/*
* Concatenate algorithm names, avoiding duplicates in the process.
* Caller must free returned string.
*/
char *
kex_names_cat(const char *a, const char *b)
{
char *ret = NULL, *tmp = NULL, *cp, *p;
size_t len;
if (a == NULL || *a == '\0')
return strdup(b);
if (b == NULL || *b == '\0')
return strdup(a);
if (strlen(b) > 1024*1024)
return NULL;
len = strlen(a) + strlen(b) + 2;
if ((tmp = cp = strdup(b)) == NULL ||
(ret = calloc(1, len)) == NULL) {
free(tmp);
return NULL;
}
strlcpy(ret, a, len);
for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
if (kex_has_any_alg(ret, p))
continue; /* Algorithm already present */
if (strlcat(ret, ",", len) >= len ||
strlcat(ret, p, len) >= len) {
free(tmp);
free(ret);
return NULL; /* Shouldn't happen */
}
}
free(tmp);
return ret;
}
/*
* Assemble a list of algorithms from a default list and a string from a
* configuration file. The user-provided string may begin with '+' to
* indicate that it should be appended to the default, '-' that the
* specified names should be removed, or '^' that they should be placed
* at the head.
*/
int
kex_assemble_names(char **listp, const char *def, const char *all)
{
char *cp, *tmp, *patterns;
char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
int r = SSH_ERR_INTERNAL_ERROR;
if (listp == NULL || def == NULL || all == NULL)
return SSH_ERR_INVALID_ARGUMENT;
if (*listp == NULL || **listp == '\0') {
if ((*listp = strdup(def)) == NULL)
return SSH_ERR_ALLOC_FAIL;
return 0;
}
list = *listp;
*listp = NULL;
if (*list == '+') {
/* Append names to default list */
if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto fail;
}
free(list);
list = tmp;
} else if (*list == '-') {
/* Remove names from default list */
if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto fail;
}
free(list);
/* filtering has already been done */
return 0;
} else if (*list == '^') {
/* Place names at head of default list */
if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto fail;
}
free(list);
list = tmp;
} else {
/* Explicit list, overrides default - just use "list" as is */
}
/*
* The supplied names may be a pattern-list. For the -list case,
* the patterns are applied above. For the +list and explicit list
* cases we need to do it now.
*/
ret = NULL;
if ((patterns = opatterns = strdup(list)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto fail;
}
/* Apply positive (i.e. non-negated) patterns from the list */
while ((cp = strsep(&patterns, ",")) != NULL) {
if (*cp == '!') {
/* negated matches are not supported here */
r = SSH_ERR_INVALID_ARGUMENT;
goto fail;
}
free(matching);
if ((matching = match_filter_allowlist(all, cp)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto fail;
}
if ((tmp = kex_names_cat(ret, matching)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto fail;
}
free(ret);
ret = tmp;
}
if (ret == NULL || *ret == '\0') {
/* An empty name-list is an error */
/* XXX better error code? */
r = SSH_ERR_INVALID_ARGUMENT;
goto fail;
}
/* success */
*listp = ret;
ret = NULL;
r = 0;
fail:
free(matching);
free(opatterns);
free(list);
free(ret);
return r;
}
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