1 files changed, 154 insertions, 49 deletions

diff --git a/kexdh.c b/kexdh.c
index e6925b186..67133e339 100644
--- a/kexdh.c
+++ b/kexdh.c
@@ -1,6 +1,6 @@
-/* $OpenBSD: kexdh.c,v 1.26 2016/05/02 10:26:04 djm Exp $ */
+/* $OpenBSD: kexdh.c,v 1.32 2019/01/21 10:40:11 djm Exp $ */
 /*
- * Copyright (c) 2001 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2019 Markus Friedl.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -30,67 +30,172 @@
 #include <sys/types.h>
 
 #include <signal.h>
-
-#include <openssl/evp.h>
+#include <stdio.h>
+#include <string.h>
 
 #include "openbsd-compat/openssl-compat.h"
+#include <openssl/dh.h>
 
-#include "ssh2.h"
 #include "sshkey.h"
-#include "cipher.h"
 #include "kex.h"
-#include "ssherr.h"
 #include "sshbuf.h"
 #include "digest.h"
+#include "ssherr.h"
+#include "dh.h"
 
 int
-kex_dh_hash(
-    int hash_alg,
-    const char *client_version_string,
-    const char *server_version_string,
-    const u_char *ckexinit, size_t ckexinitlen,
-    const u_char *skexinit, size_t skexinitlen,
-    const u_char *serverhostkeyblob, size_t sbloblen,
-    const BIGNUM *client_dh_pub,
-    const BIGNUM *server_dh_pub,
-    const BIGNUM *shared_secret,
-    u_char *hash, size_t *hashlen)
+kex_dh_keygen(struct kex *kex)
 {
-        struct sshbuf *b;
-        int r;
-
-        if (*hashlen < ssh_digest_bytes(hash_alg))
+        switch (kex->kex_type) {
+        case KEX_DH_GRP1_SHA1:
+                kex->dh = dh_new_group1();
+                break;
+        case KEX_DH_GRP14_SHA1:
+        case KEX_DH_GRP14_SHA256:
+                kex->dh = dh_new_group14();
+                break;
+        case KEX_DH_GRP16_SHA512:
+                kex->dh = dh_new_group16();
+                break;
+        case KEX_DH_GRP18_SHA512:
+                kex->dh = dh_new_group18();
+                break;
+        default:
                 return SSH_ERR_INVALID_ARGUMENT;
-        if ((b = sshbuf_new()) == NULL)
-                return SSH_ERR_ALLOC_FAIL;
-        if ((r = sshbuf_put_cstring(b, client_version_string)) != 0 ||
-            (r = sshbuf_put_cstring(b, server_version_string)) != 0 ||
-            /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
-            (r = sshbuf_put_u32(b, ckexinitlen+1)) != 0 ||
-            (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
-            (r = sshbuf_put(b, ckexinit, ckexinitlen)) != 0 ||
-            (r = sshbuf_put_u32(b, skexinitlen+1)) != 0 ||
-            (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
-            (r = sshbuf_put(b, skexinit, skexinitlen)) != 0 ||
-            (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) != 0 ||
-            (r = sshbuf_put_bignum2(b, client_dh_pub)) != 0 ||
-            (r = sshbuf_put_bignum2(b, server_dh_pub)) != 0 ||
-            (r = sshbuf_put_bignum2(b, shared_secret)) != 0) {
-                sshbuf_free(b);
-                return r;
         }
-#ifdef DEBUG_KEX
-        sshbuf_dump(b, stderr);
+        if (kex->dh == NULL)
+                return SSH_ERR_ALLOC_FAIL;
+        return (dh_gen_key(kex->dh, kex->we_need * 8));
+}
+
+int
+kex_dh_compute_key(struct kex *kex, BIGNUM *dh_pub, struct sshbuf *out)
+{
+        BIGNUM *shared_secret = NULL;
+        u_char *kbuf = NULL;
+        size_t klen = 0;
+        int kout, r;
+
+#ifdef DEBUG_KEXDH
+        fprintf(stderr, "dh_pub= ");
+        BN_print_fp(stderr, dh_pub);
+        fprintf(stderr, "\n");
+        debug("bits %d", BN_num_bits(dh_pub));
+        DHparams_print_fp(stderr, kex->dh);
+        fprintf(stderr, "\n");
 #endif
-        if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) {
-                sshbuf_free(b);
-                return SSH_ERR_LIBCRYPTO_ERROR;
+
+        if (!dh_pub_is_valid(kex->dh, dh_pub)) {
+                r = SSH_ERR_MESSAGE_INCOMPLETE;
+                goto out;
+        }
+        klen = DH_size(kex->dh);
+        if ((kbuf = malloc(klen)) == NULL ||
+            (shared_secret = BN_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if ((kout = DH_compute_key(kbuf, dh_pub, kex->dh)) < 0 ||
+            BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
+                r = SSH_ERR_LIBCRYPTO_ERROR;
+                goto out;
         }
-        sshbuf_free(b);
-        *hashlen = ssh_digest_bytes(hash_alg);
-#ifdef DEBUG_KEX
-        dump_digest("hash", hash, *hashlen);
+#ifdef DEBUG_KEXDH
+        dump_digest("shared secret", kbuf, kout);
 #endif
-        return 0;
+        r = sshbuf_put_bignum2(out, shared_secret);
+ out:
+        freezero(kbuf, klen);
+        BN_clear_free(shared_secret);
+        return r;
+}
+
+int
+kex_dh_keypair(struct kex *kex)
+{
+        const BIGNUM *pub_key;
+        struct sshbuf *buf = NULL;
+        int r;
+
+        if ((r = kex_dh_keygen(kex)) != 0)
+                return r;
+        DH_get0_key(kex->dh, &pub_key, NULL);
+        if ((buf = sshbuf_new()) == NULL)
+                return SSH_ERR_ALLOC_FAIL;
+        if ((r = sshbuf_put_bignum2(buf, pub_key)) != 0 ||
+            (r = sshbuf_get_u32(buf, NULL)) != 0)
+                goto out;
+#ifdef DEBUG_KEXDH
+        DHparams_print_fp(stderr, kex->dh);
+        fprintf(stderr, "pub= ");
+        BN_print_fp(stderr, pub_key);
+        fprintf(stderr, "\n");
+#endif
+        kex->client_pub = buf;
+        buf = NULL;
+ out:
+        sshbuf_free(buf);
+        return r;
+}
+
+int
+kex_dh_enc(struct kex *kex, const struct sshbuf *client_blob,
+    struct sshbuf **server_blobp, struct sshbuf **shared_secretp)
+{
+        const BIGNUM *pub_key;
+        struct sshbuf *server_blob = NULL;
+        int r;
+
+        *server_blobp = NULL;
+        *shared_secretp = NULL;
+
+        if ((r = kex_dh_keygen(kex)) != 0)
+                goto out;
+        DH_get0_key(kex->dh, &pub_key, NULL);
+        if ((server_blob = sshbuf_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if ((r = sshbuf_put_bignum2(server_blob, pub_key)) != 0 ||
+            (r = sshbuf_get_u32(server_blob, NULL)) != 0)
+                goto out;
+        if ((r = kex_dh_dec(kex, client_blob, shared_secretp)) != 0)
+                goto out;
+        *server_blobp = server_blob;
+        server_blob = NULL;
+ out:
+        DH_free(kex->dh);
+        kex->dh = NULL;
+        sshbuf_free(server_blob);
+        return r;
+}
+
+int
+kex_dh_dec(struct kex *kex, const struct sshbuf *dh_blob,
+    struct sshbuf **shared_secretp)
+{
+        struct sshbuf *buf = NULL;
+        BIGNUM *dh_pub = NULL;
+        int r;
+
+        *shared_secretp = NULL;
+
+        if ((buf = sshbuf_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if ((r = sshbuf_put_stringb(buf, dh_blob)) != 0 ||
+            (r = sshbuf_get_bignum2(buf, &dh_pub)) != 0)
+                goto out;
+        sshbuf_reset(buf);
+        if ((r = kex_dh_compute_key(kex, dh_pub, buf)) != 0)
+                goto out;
+        *shared_secretp = buf;
+        buf = NULL;
+ out:
+        DH_free(kex->dh);
+        kex->dh = NULL;
+        sshbuf_free(buf);
+        return r;
 }
 #endif /* WITH_OPENSSL */