Mercurial > dropbear
view svr-kex.c @ 1653:76189c9ffea2
External Public-Key Authentication API (#72)
* Implemented dynamic loading of an external plug-in shared library to delegate public key authentication
* Moved conditional compilation of the plugin infrastructure into the configure.ac script to be able to add -ldl to dropbear build only when the flag is enabled
* Added tags file to the ignore list
* Updated API to have the constructor to return function pointers in the pliugin instance. Added support for passing user name to the checkpubkey function. Added options to the session returned by the plugin and have dropbear to parse and process them
* Added -rdynamic to the linker flags when EPKA is enabled
* Changed the API to pass a previously created session to the checkPubKey function (created during preauth)
* Added documentation to the API
* Added parameter addrstring to plugin creation function
* Modified the API to retrieve the auth options. Instead of having them as field of the EPKASession struct, they are stored internally (plugin-dependent) in the plugin/session and retrieved through a pointer to a function (in the session)
* Changed option string to be a simple char * instead of unsigned char *
author | fabriziobertocci <fabriziobertocci@gmail.com> |
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date | Wed, 15 May 2019 09:43:57 -0400 |
parents | 2f64cb3d3007 |
children | d32bcb5c557d |
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/* * Dropbear - a SSH2 server * * Copyright (c) 2002,2003 Matt Johnston * Copyright (c) 2004 by Mihnea Stoenescu * All rights reserved. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #include "includes.h" #include "dbutil.h" #include "algo.h" #include "buffer.h" #include "session.h" #include "kex.h" #include "ssh.h" #include "packet.h" #include "bignum.h" #include "dbrandom.h" #include "runopts.h" #include "ecc.h" #include "gensignkey.h" static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs); /* Handle a diffie-hellman key exchange initialisation. This involves * calculating a session key reply value, and corresponding hash. These * are carried out by send_msg_kexdh_reply(). recv_msg_kexdh_init() calls * that function, then brings the new keys into use */ void recv_msg_kexdh_init() { DEF_MP_INT(dh_e); buffer *ecdh_qs = NULL; TRACE(("enter recv_msg_kexdh_init")) if (!ses.kexstate.recvkexinit) { dropbear_exit("Premature kexdh_init message received"); } switch (ses.newkeys->algo_kex->mode) { #if DROPBEAR_NORMAL_DH case DROPBEAR_KEX_NORMAL_DH: m_mp_init(&dh_e); if (buf_getmpint(ses.payload, &dh_e) != DROPBEAR_SUCCESS) { dropbear_exit("Bad kex value"); } break; #endif #if DROPBEAR_ECDH case DROPBEAR_KEX_ECDH: #endif #if DROPBEAR_CURVE25519 case DROPBEAR_KEX_CURVE25519: #endif #if DROPBEAR_ECDH || DROPBEAR_CURVE25519 ecdh_qs = buf_getstringbuf(ses.payload); break; #endif } if (ses.payload->pos != ses.payload->len) { dropbear_exit("Bad kex value"); } send_msg_kexdh_reply(&dh_e, ecdh_qs); mp_clear(&dh_e); if (ecdh_qs) { buf_free(ecdh_qs); ecdh_qs = NULL; } send_msg_newkeys(); ses.requirenext = SSH_MSG_NEWKEYS; TRACE(("leave recv_msg_kexdh_init")) } #if DROPBEAR_DELAY_HOSTKEY static void svr_ensure_hostkey() { const char* fn = NULL; enum signkey_type type = ses.newkeys->algo_hostkey; void **hostkey = signkey_key_ptr(svr_opts.hostkey, type); int ret = DROPBEAR_FAILURE; if (hostkey && *hostkey) { return; } switch (type) { #if DROPBEAR_RSA case DROPBEAR_SIGNKEY_RSA: fn = RSA_PRIV_FILENAME; break; #endif #if DROPBEAR_DSS case DROPBEAR_SIGNKEY_DSS: fn = DSS_PRIV_FILENAME; break; #endif #if DROPBEAR_ECDSA case DROPBEAR_SIGNKEY_ECDSA_NISTP256: case DROPBEAR_SIGNKEY_ECDSA_NISTP384: case DROPBEAR_SIGNKEY_ECDSA_NISTP521: fn = ECDSA_PRIV_FILENAME; break; #endif default: dropbear_assert(0); } if (readhostkey(fn, svr_opts.hostkey, &type) == DROPBEAR_SUCCESS) { return; } if (signkey_generate(type, 0, fn, 1) == DROPBEAR_FAILURE) { goto out; } ret = readhostkey(fn, svr_opts.hostkey, &type); if (ret == DROPBEAR_SUCCESS) { char *fp = NULL; unsigned int len; buffer *key_buf = buf_new(MAX_PUBKEY_SIZE); buf_put_pub_key(key_buf, svr_opts.hostkey, type); buf_setpos(key_buf, 4); len = key_buf->len - key_buf->pos; fp = sign_key_fingerprint(buf_getptr(key_buf, len), len); dropbear_log(LOG_INFO, "Generated hostkey %s, fingerprint is %s", fn, fp); m_free(fp); buf_free(key_buf); } out: if (ret == DROPBEAR_FAILURE) { dropbear_exit("Couldn't read or generate hostkey %s", fn); } } #endif /* Generate our side of the diffie-hellman key exchange value (dh_f), and * calculate the session key using the diffie-hellman algorithm. Following * that, the session hash is calculated, and signed with RSA or DSS. The * result is sent to the client. * * See the transport RFC4253 section 8 for details * or RFC5656 section 4 for elliptic curve variant. */ static void send_msg_kexdh_reply(mp_int *dh_e, buffer *ecdh_qs) { TRACE(("enter send_msg_kexdh_reply")) /* we can start creating the kexdh_reply packet */ CHECKCLEARTOWRITE(); #if DROPBEAR_DELAY_HOSTKEY if (svr_opts.delay_hostkey) { svr_ensure_hostkey(); } #endif #if DROPBEAR_FUZZ if (fuzz.fuzzing && fuzz.skip_kexmaths) { fuzz_fake_send_kexdh_reply(); return; } #endif buf_putbyte(ses.writepayload, SSH_MSG_KEXDH_REPLY); buf_put_pub_key(ses.writepayload, svr_opts.hostkey, ses.newkeys->algo_hostkey); switch (ses.newkeys->algo_kex->mode) { #if DROPBEAR_NORMAL_DH case DROPBEAR_KEX_NORMAL_DH: { struct kex_dh_param * dh_param = gen_kexdh_param(); kexdh_comb_key(dh_param, dh_e, svr_opts.hostkey); /* put f */ buf_putmpint(ses.writepayload, &dh_param->pub); free_kexdh_param(dh_param); } break; #endif #if DROPBEAR_ECDH case DROPBEAR_KEX_ECDH: { struct kex_ecdh_param *ecdh_param = gen_kexecdh_param(); kexecdh_comb_key(ecdh_param, ecdh_qs, svr_opts.hostkey); buf_put_ecc_raw_pubkey_string(ses.writepayload, &ecdh_param->key); free_kexecdh_param(ecdh_param); } break; #endif #if DROPBEAR_CURVE25519 case DROPBEAR_KEX_CURVE25519: { struct kex_curve25519_param *param = gen_kexcurve25519_param(); kexcurve25519_comb_key(param, ecdh_qs, svr_opts.hostkey); buf_putstring(ses.writepayload, (const char*)param->pub, CURVE25519_LEN); free_kexcurve25519_param(param); } break; #endif } /* calc the signature */ buf_put_sign(ses.writepayload, svr_opts.hostkey, ses.newkeys->algo_hostkey, ses.hash); /* the SSH_MSG_KEXDH_REPLY is done */ encrypt_packet(); TRACE(("leave send_msg_kexdh_reply")) }