5 files changed, 688 insertions, 9 deletions

diff --git a/Makefile.in b/Makefile.in
index 13256c2af..b494ac7ca 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -65,6 +65,7 @@ MANFMT=@MANFMT@
 TARGETS=ssh$(EXEEXT) sshd$(EXEEXT) ssh-add$(EXEEXT) ssh-keygen$(EXEEXT) ssh-keyscan${EXEEXT} ssh-keysign${EXEEXT} ssh-pkcs11-helper$(EXEEXT) ssh-agent$(EXEEXT) scp$(EXEEXT) sftp-server$(EXEEXT) sftp$(EXEEXT)
 
 LIBOPENSSH_OBJS=\
+        ssh_api.o \
         ssherr.o \
         sshbuf.o \
         sshkey.o \
@@ -75,20 +76,22 @@ LIBOPENSSH_OBJS=\
         bitmap.o
 
 LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
-        authfd.o authfile.o bufaux.o bufbn.o buffer.o \
+        authfd.o authfile.o bufaux.o bufbn.o bufec.o buffer.o \
         canohost.o channels.o cipher.o cipher-aes.o cipher-aesctr.o \
         cipher-bf1.o cipher-ctr.o cipher-3des1.o cleanup.o \
         compat.o crc32.o deattack.o fatal.o hostfile.o \
         log.o match.o md-sha256.o moduli.o nchan.o packet.o opacket.o \
         readpass.o rsa.o ttymodes.o xmalloc.o addrmatch.o \
-        atomicio.o key.o dispatch.o kex.o mac.o uidswap.o uuencode.o misc.o \
+        atomicio.o key.o dispatch.o mac.o uidswap.o uuencode.o misc.o \
         monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-rsa.o dh.o \
-        kexdh.o kexgex.o kexdhc.o kexgexc.o bufec.o kexecdh.o kexecdhc.o \
         msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
         ssh-pkcs11.o smult_curve25519_ref.o \
-        kexc25519.o kexc25519c.o poly1305.o chacha.o cipher-chachapoly.o \
+        poly1305.o chacha.o cipher-chachapoly.o \
         ssh-ed25519.o digest-openssl.o digest-libc.o hmac.o \
-        sc25519.o ge25519.o fe25519.o ed25519.o verify.o hash.o blocks.o
+        sc25519.o ge25519.o fe25519.o ed25519.o verify.o hash.o blocks.o \
+        kex.o kexdh.o kexgex.o kexecdh.o kexc25519.o \
+        kexdhc.o kexgexc.o kexecdhc.o kexc25519c.o \
+        kexdhs.o kexgexs.o kexecdhs.o kexc25519s.o
 
 SSHOBJS= ssh.o readconf.o clientloop.o sshtty.o \
         sshconnect.o sshconnect1.o sshconnect2.o mux.o \
@@ -101,8 +104,7 @@ SSHDOBJS=sshd.o auth-rhosts.o auth-passwd.o auth-rsa.o auth-rh-rsa.o \
         auth-chall.o auth2-chall.o groupaccess.o \
         auth-skey.o auth-bsdauth.o auth2-hostbased.o auth2-kbdint.o \
         auth2-none.o auth2-passwd.o auth2-pubkey.o \
-        monitor_mm.o monitor.o monitor_wrap.o kexdhs.o kexgexs.o kexecdhs.o \
-        kexc25519s.o auth-krb5.o \
+        monitor_mm.o monitor.o monitor_wrap.o auth-krb5.o \
         auth2-gss.o gss-serv.o gss-serv-krb5.o \
         loginrec.o auth-pam.o auth-shadow.o auth-sia.o md5crypt.o \
         sftp-server.o sftp-common.o \
diff --git a/packet.c b/packet.c
index 3306e4d6c..cf9d3648b 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.201 2015/01/19 19:52:16 markus Exp $ */
+/* $OpenBSD: packet.c,v 1.202 2015/01/19 20:30:23 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -233,6 +233,8 @@ ssh_alloc_session_state(void)
             (state->incoming_packet = sshbuf_new()) == NULL)
                 goto fail;
         TAILQ_INIT(&state->outgoing);
+        TAILQ_INIT(&ssh->private_keys);
+        TAILQ_INIT(&ssh->public_keys);
         state->connection_in = -1;
         state->connection_out = -1;
         state->max_packet_size = 32768;
diff --git a/packet.h b/packet.h
index d9b56c301..069af2eae 100644
--- a/packet.h
+++ b/packet.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.h,v 1.63 2015/01/19 20:07:45 markus Exp $ */
+/* $OpenBSD: packet.h,v 1.64 2015/01/19 20:30:23 markus Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -34,6 +34,11 @@ struct session_state;	/* private session data */
 
 #include "dispatch.h"   /* typedef, DISPATCH_MAX */
 
+struct key_entry {
+        TAILQ_ENTRY(key_entry) next;
+        struct sshkey *key;
+};
+
 struct ssh {
         /* Session state */
         struct session_state *state;
@@ -52,6 +57,13 @@ struct ssh {
 
         /* datafellows */
         int compat;
+
+        /* Lists for private and public keys */
+        TAILQ_HEAD(, key_entry) private_keys;
+        TAILQ_HEAD(, key_entry) public_keys;
+
+        /* APP data */
+        void *app_data;
 };
 
 struct ssh *ssh_alloc_session_state(void);
diff --git a/ssh_api.c b/ssh_api.c
new file mode 100644
index 000000000..1df995c94
--- /dev/null
+++ b/ssh_api.c
@@ -0,0 +1,527 @@
+/* $OpenBSD: ssh_api.c,v 1.1 2015/01/19 20:30:23 markus Exp $ */
+/*
+ * Copyright (c) 2012 Markus Friedl.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "includes.h"
+
+#include "ssh1.h" /* For SSH_MSG_NONE */
+#include "ssh_api.h"
+#include "compat.h"
+#include "log.h"
+#include "authfile.h"
+#include "sshkey.h"
+#include "misc.h"
+#include "ssh1.h"
+#include "ssh2.h"
+#include "version.h"
+#include "myproposal.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+
+#include <string.h>
+
+int     _ssh_exchange_banner(struct ssh *);
+int     _ssh_send_banner(struct ssh *, char **);
+int     _ssh_read_banner(struct ssh *, char **);
+int     _ssh_order_hostkeyalgs(struct ssh *);
+int     _ssh_verify_host_key(struct sshkey *, struct ssh *);
+struct sshkey *_ssh_host_public_key(int, struct ssh *);
+struct sshkey *_ssh_host_private_key(int, struct ssh *);
+int     _ssh_host_key_sign(struct sshkey *, struct sshkey *, u_char **,
+    size_t *, u_char *, size_t, u_int);
+
+/*
+ * stubs for the server side implementation of kex.
+ * disable privsep so our stubs will never be called.
+ */
+int     use_privsep = 0;
+int     mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
+    u_char *, u_int, u_int);
+DH      *mm_choose_dh(int, int, int);
+
+/* Define these two variables here so that they are part of the library */
+u_char *session_id2 = NULL;
+u_int session_id2_len = 0;
+
+int
+mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
+    u_char *data, u_int datalen, u_int compat)
+{
+        return (-1);
+}
+
+DH *
+mm_choose_dh(int min, int nbits, int max)
+{
+        return (NULL);
+}
+
+/* API */
+
+int
+ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
+{
+        char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
+        struct ssh *ssh;
+        char **proposal;
+        static int called;
+        int r;
+
+        if (!called) {
+                OpenSSL_add_all_algorithms();
+                called = 1;
+        }
+
+        ssh = ssh_packet_set_connection(NULL, -1, -1);
+        if (is_server)
+                ssh_packet_set_server(ssh);
+
+        /* Initialize key exchange */
+        proposal = kex_params ? kex_params->proposal : myproposal;
+        if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) {
+                ssh_free(ssh);
+                return r;
+        }
+        ssh->kex->server = is_server;
+        if (is_server) {
+#ifdef WITH_OPENSSL
+                ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
+                ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
+                ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
+                ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
+                ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
+#endif /* WITH_OPENSSL */
+                ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server;
+                ssh->kex->load_host_public_key=&_ssh_host_public_key;
+                ssh->kex->load_host_private_key=&_ssh_host_private_key;
+                ssh->kex->sign=&_ssh_host_key_sign;
+        } else {
+#ifdef WITH_OPENSSL
+                ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
+                ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
+                ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
+                ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
+                ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
+#endif /* WITH_OPENSSL */
+                ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client;
+                ssh->kex->verify_host_key =&_ssh_verify_host_key;
+        }
+        *sshp = ssh;
+        return 0;
+}
+
+void
+ssh_free(struct ssh *ssh)
+{
+        struct key_entry *k;
+
+        ssh_packet_close(ssh);
+        /*
+         * we've only created the public keys variants in case we
+         * are a acting as a server.
+         */
+        while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
+                TAILQ_REMOVE(&ssh->public_keys, k, next);
+                if (ssh->kex && ssh->kex->server)
+                        sshkey_free(k->key);
+                free(k);
+        }
+        while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
+                TAILQ_REMOVE(&ssh->private_keys, k, next);
+                free(k);
+        }
+        if (ssh->kex)
+                kex_free(ssh->kex);
+        free(ssh);
+}
+
+void
+ssh_set_app_data(struct ssh *ssh, void *app_data)
+{
+        ssh->app_data = app_data;
+}
+
+void *
+ssh_get_app_data(struct ssh *ssh)
+{
+        return ssh->app_data;
+}
+
+/* Returns < 0 on error, 0 otherwise */
+int
+ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
+{
+        struct sshkey *pubkey = NULL;
+        struct key_entry *k = NULL, *k_prv = NULL;
+        int r;
+
+        if (ssh->kex->server) {
+                if ((r = sshkey_from_private(key, &pubkey)) != 0)
+                        return r;
+                if ((k = malloc(sizeof(*k))) == NULL ||
+                    (k_prv = malloc(sizeof(*k_prv))) == NULL) {
+                        free(k);
+                        sshkey_free(pubkey);
+                        return SSH_ERR_ALLOC_FAIL;
+                }
+                k_prv->key = key;
+                TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
+
+                /* add the public key, too */
+                k->key = pubkey;
+                TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
+                r = 0;
+        } else {
+                if ((k = malloc(sizeof(*k))) == NULL)
+                        return SSH_ERR_ALLOC_FAIL;
+                k->key = key;
+                TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
+                r = 0;
+        }
+
+        return r;
+}
+
+int
+ssh_set_verify_host_key_callback(struct ssh *ssh,
+    int (*cb)(struct sshkey *, struct ssh *))
+{
+        if (cb == NULL || ssh->kex == NULL)
+                return SSH_ERR_INVALID_ARGUMENT;
+
+        ssh->kex->verify_host_key = cb;
+
+        return 0;
+}
+
+int
+ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
+{
+        return sshbuf_put(ssh_packet_get_input(ssh), data, len);
+}
+
+int
+ssh_packet_next(struct ssh *ssh, u_char *typep)
+{
+        int r;
+        u_int32_t seqnr;
+        u_char type;
+
+        /*
+         * Try to read a packet. Return SSH_MSG_NONE if no packet or not
+         * enough data.
+         */
+        *typep = SSH_MSG_NONE;
+        if (ssh->kex->client_version_string == NULL ||
+            ssh->kex->server_version_string == NULL)
+                return _ssh_exchange_banner(ssh);
+        /*
+         * If we enough data and a dispatch function then
+         * call the function and get the next packet.
+         * Otherwise return the packet type to the caller so it
+         * can decide how to go on.
+         *
+         * We will only call the dispatch function for:
+         *     20-29    Algorithm negotiation
+         *     30-49    Key exchange method specific (numbers can be reused for
+         *              different authentication methods)
+         */
+        for (;;) {
+                if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
+                        return r;
+                if (type > 0 && type < DISPATCH_MAX &&
+                    type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
+                    ssh->dispatch[type] != NULL) {
+                        if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
+                                return r;
+                } else {
+                        *typep = type;
+                        return 0;
+                }
+        }
+}
+
+const u_char *
+ssh_packet_payload(struct ssh *ssh, size_t *lenp)
+{
+        return sshpkt_ptr(ssh, lenp);
+}
+
+int
+ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
+{
+        int r;
+
+        if ((r = sshpkt_start(ssh, type)) != 0 ||
+            (r = sshpkt_put(ssh, data, len)) != 0 ||
+            (r = sshpkt_send(ssh)) != 0)
+                return r;
+        return 0;
+}
+
+const u_char *
+ssh_output_ptr(struct ssh *ssh, size_t *len)
+{
+        struct sshbuf *output = ssh_packet_get_output(ssh);
+
+        *len = sshbuf_len(output);
+        return sshbuf_ptr(output);
+}
+
+int
+ssh_output_consume(struct ssh *ssh, size_t len)
+{
+        return sshbuf_consume(ssh_packet_get_output(ssh), len);
+}
+
+int
+ssh_output_space(struct ssh *ssh, size_t len)
+{
+        return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
+}
+
+int
+ssh_input_space(struct ssh *ssh, size_t len)
+{
+        return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
+}
+
+/* Read other side's version identification. */
+int
+_ssh_read_banner(struct ssh *ssh, char **bannerp)
+{
+        struct sshbuf *input;
+        const char *s;
+        char buf[256], remote_version[256];     /* must be same size! */
+        const char *mismatch = "Protocol mismatch.\r\n";
+        int r, remote_major, remote_minor;
+        size_t i, n, j, len;
+
+        *bannerp = NULL;
+        input = ssh_packet_get_input(ssh);
+        len = sshbuf_len(input);
+        s = (const char *)sshbuf_ptr(input);
+        for (j = n = 0;;) {
+                for (i = 0; i < sizeof(buf) - 1; i++) {
+                        if (j >= len)
+                                return (0);
+                        buf[i] = s[j++];
+                        if (buf[i] == '\r') {
+                                buf[i] = '\n';
+                                buf[i + 1] = 0;
+                                continue;               /**XXX wait for \n */
+                        }
+                        if (buf[i] == '\n') {
+                                buf[i + 1] = 0;
+                                break;
+                        }
+                }
+                buf[sizeof(buf) - 1] = 0;
+                if (strncmp(buf, "SSH-", 4) == 0)
+                        break;
+                debug("ssh_exchange_identification: %s", buf);
+                if (ssh->kex->server || ++n > 65536) {
+                        if ((r = sshbuf_put(ssh_packet_get_output(ssh),
+                           mismatch, strlen(mismatch))) != 0)
+                                return r;
+                        return SSH_ERR_NO_PROTOCOL_VERSION;
+                }
+        }
+        if ((r = sshbuf_consume(input, j)) != 0)
+                return r;
+
+        /*
+         * Check that the versions match.  In future this might accept
+         * several versions and set appropriate flags to handle them.
+         */
+        if (sscanf(buf, "SSH-%d.%d-%[^\n]\n",
+            &remote_major, &remote_minor, remote_version) != 3)
+                return SSH_ERR_INVALID_FORMAT;
+        debug("Remote protocol version %d.%d, remote software version %.100s",
+            remote_major, remote_minor, remote_version);
+
+        ssh->compat = compat_datafellows(remote_version);
+        if  (remote_major == 1 && remote_minor == 99) {
+                remote_major = 2;
+                remote_minor = 0;
+        }
+        if (remote_major != 2)
+                return SSH_ERR_PROTOCOL_MISMATCH;
+        enable_compat20();
+        chop(buf);
+        debug("Remote version string %.100s", buf);
+        if ((*bannerp = strdup(buf)) == NULL)
+                return SSH_ERR_ALLOC_FAIL;
+        return 0;
+}
+
+/* Send our own protocol version identification. */
+int
+_ssh_send_banner(struct ssh *ssh, char **bannerp)
+{
+        char buf[256];
+        int r;
+
+        snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION);
+        if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0)
+                return r;
+        chop(buf);
+        debug("Local version string %.100s", buf);
+        if ((*bannerp = strdup(buf)) == NULL)
+                return SSH_ERR_ALLOC_FAIL;
+        return 0;
+}
+
+int
+_ssh_exchange_banner(struct ssh *ssh)
+{
+        struct kex *kex = ssh->kex;
+        int r;
+
+        /*
+         * if _ssh_read_banner() cannot parse a full version string
+         * it will return NULL and we end up calling it again.
+         */
+
+        r = 0;
+        if (kex->server) {
+                if (kex->server_version_string == NULL)
+                        r = _ssh_send_banner(ssh, &kex->server_version_string);
+                if (r == 0 &&
+                    kex->server_version_string != NULL &&
+                    kex->client_version_string == NULL)
+                        r = _ssh_read_banner(ssh, &kex->client_version_string);
+        } else {
+                if (kex->server_version_string == NULL)
+                        r = _ssh_read_banner(ssh, &kex->server_version_string);
+                if (r == 0 &&
+                    kex->server_version_string != NULL &&
+                    kex->client_version_string == NULL)
+                        r = _ssh_send_banner(ssh, &kex->client_version_string);
+        }
+        if (r != 0)
+                return r;
+        /* start initial kex as soon as we have exchanged the banners */
+        if (kex->server_version_string != NULL &&
+            kex->client_version_string != NULL) {
+                if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
+                    (r = kex_send_kexinit(ssh)) != 0)
+                        return r;
+        }
+        return 0;
+}
+
+struct sshkey *
+_ssh_host_public_key(int type, struct ssh *ssh)
+{
+        struct key_entry *k;
+
+        debug3("%s: need %d", __func__, type);
+        TAILQ_FOREACH(k, &ssh->public_keys, next) {
+                debug3("%s: check %s", __func__, sshkey_type(k->key));
+                if (k->key->type == type)
+                        return (k->key);
+        }
+        return (NULL);
+}
+
+struct sshkey *
+_ssh_host_private_key(int type, struct ssh *ssh)
+{
+        struct key_entry *k;
+
+        debug3("%s: need %d", __func__, type);
+        TAILQ_FOREACH(k, &ssh->private_keys, next) {
+                debug3("%s: check %s", __func__, sshkey_type(k->key));
+                if (k->key->type == type)
+                        return (k->key);
+        }
+        return (NULL);
+}
+
+int
+_ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
+{
+        struct key_entry *k;
+
+        debug3("%s: need %s", __func__, sshkey_type(hostkey));
+        TAILQ_FOREACH(k, &ssh->public_keys, next) {
+                debug3("%s: check %s", __func__, sshkey_type(k->key));
+                if (sshkey_equal_public(hostkey, k->key))
+                        return (0);     /* ok */
+        }
+        return (-1);    /* failed */
+}
+
+/* offer hostkey algorithms in kexinit depending on registered keys */
+int
+_ssh_order_hostkeyalgs(struct ssh *ssh)
+{
+        struct key_entry *k;
+        char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
+        char **proposal;
+        size_t maxlen;
+        int ktype, r;
+
+        /* XXX we de-serialize ssh->kex->my, modify it, and change it */
+        if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
+                return r;
+        orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
+        if ((oavail = avail = strdup(orig)) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        maxlen = strlen(avail) + 1;
+        if ((replace = calloc(1, maxlen)) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        *replace = '\0';
+        while ((alg = strsep(&avail, ",")) && *alg != '\0') {
+                if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
+                        continue;
+                TAILQ_FOREACH(k, &ssh->public_keys, next) {
+                        if (k->key->type == ktype ||
+                            (sshkey_is_cert(k->key) && k->key->type ==
+                            sshkey_type_plain(ktype))) {
+                                if (*replace != '\0')
+                                        strlcat(replace, ",", maxlen);
+                                strlcat(replace, alg, maxlen);
+                                break;
+                        }
+                }
+        }
+        if (*replace != '\0') {
+                debug2("%s: orig/%d    %s", __func__, ssh->kex->server, orig);
+                debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
+                free(orig);
+                proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
+                replace = NULL; /* owned by proposal */
+                r = kex_prop2buf(ssh->kex->my, proposal);
+        }
+ out:
+        free(oavail);
+        free(replace);
+        kex_prop_free(proposal);
+        return r;
+}
+
+int
+_ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey,
+    u_char **signature, size_t *slen, u_char *data, size_t dlen, u_int compat)
+{
+        return sshkey_sign(privkey, signature, slen, data, dlen, compat);
+}
diff --git a/ssh_api.h b/ssh_api.h
new file mode 100644
index 000000000..a7e14e06e
--- /dev/null
+++ b/ssh_api.h
@@ -0,0 +1,136 @@
+/* $OpenBSD: ssh_api.h,v 1.1 2015/01/19 20:30:23 markus Exp $ */
+/*
+ * Copyright (c) 2012 Markus Friedl.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef API_H
+#define API_H
+
+#include <sys/queue.h>
+#include <sys/types.h>
+#include <signal.h>
+
+#include "cipher.h"
+#include "sshkey.h"
+#include "kex.h"
+#include "ssh.h"
+#include "ssh2.h"
+#include "packet.h"
+
+struct kex_params {
+        char *proposal[PROPOSAL_MAX];
+};
+
+/* public SSH API functions */
+
+/*
+ * ssh_init() create a ssh connection object with given (optional)
+ * key exchange parameters.
+ */
+int     ssh_init(struct ssh **, int is_server, struct kex_params *kex_params);
+
+/*
+ * release ssh connection state.
+ */
+void    ssh_free(struct ssh *);
+
+/*
+ * attach application specific data to the connection state
+ */
+void    ssh_set_app_data(struct ssh *, void *);
+void    *ssh_get_app_data(struct ssh *);
+
+/*
+ * ssh_add_hostkey() registers a private/public hostkey for an ssh
+ * connection.
+ * ssh_add_hostkey() needs to be called before a key exchange is
+ * initiated with ssh_packet_next().
+ * private hostkeys are required if we need to act as a server.
+ * public hostkeys are used to verify the servers hostkey.
+ */
+int     ssh_add_hostkey(struct ssh *ssh, struct sshkey *key);
+
+/*
+ * ssh_set_verify_host_key_callback() registers a callback function
+ * which should be called instead of the default verification. The
+ * function given must return 0 if the hostkey is ok, -1 if the
+ * verification has failed.
+ */
+int     ssh_set_verify_host_key_callback(struct ssh *ssh,
+    int (*cb)(struct sshkey *, struct ssh *));
+
+/*
+ * ssh_packet_next() advances to the next input packet and returns
+ * the packet type in typep.
+ * ssh_packet_next() works by processing an input byte-stream,
+ * decrypting the received data and hiding the key-exchange from
+ * the caller.
+ * ssh_packet_next() sets typep if there is no new packet available.
+ * in this case the caller must fill the input byte-stream by passing
+ * the data received over network to ssh_input_append().
+ * additinally, the caller needs to send the resulting output
+ * byte-stream back over the network. otherwise the key exchange
+ * would not proceed. the output byte-stream is accessed through
+ * ssh_output_ptr().
+ */
+int     ssh_packet_next(struct ssh *ssh, u_char *typep);
+
+/*
+ * ssh_packet_payload() returns a pointer to the raw payload data of
+ * the current input packet and the length of this payload.
+ * the payload is accessible until ssh_packet_next() is called again.
+ */
+const u_char    *ssh_packet_payload(struct ssh *ssh, size_t *lenp);
+
+/*
+ * ssh_packet_put() creates an encrypted packet with the given type
+ * and payload.
+ * the encrypted packet is appended to the output byte-stream.
+ */
+int     ssh_packet_put(struct ssh *ssh, int type, const u_char *data,
+    size_t len);
+
+/*
+ * ssh_input_space() checks if 'len' bytes can be appended to the
+ * input byte-stream.
+ */
+int     ssh_input_space(struct ssh *ssh, size_t len);
+
+/*
+ * ssh_input_append() appends data to the input byte-stream.
+ */
+int     ssh_input_append(struct ssh *ssh, const u_char *data, size_t len);
+
+/*
+ * ssh_output_space() checks if 'len' bytes can be appended to the
+ * output byte-stream. XXX
+ */
+int     ssh_output_space(struct ssh *ssh, size_t len);
+
+/*
+ * ssh_output_ptr() retrieves both a pointer and the length of the
+ * current output byte-stream. the bytes need to be sent over the
+ * network. the number of bytes that have been successfully sent can
+ * be removed from the output byte-stream with ssh_output_consume().
+ */
+const u_char    *ssh_output_ptr(struct ssh *ssh, size_t *len);
+
+/*
+ * ssh_output_consume() removes the given number of bytes from
+ * the output byte-stream.
+ */
+int     ssh_output_consume(struct ssh *ssh, size_t len);
+
+#endif