1 files changed, 330 insertions, 0 deletions
diff --git a/kex-names.c b/kex-names.c
new file mode 100644
index 0000000..339eb1c
--- /dev/null
+++ b/kex-names.c
@@ -0,0 +1,330 @@
+/* $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;
+}