1 files changed, 298 insertions, 0 deletions
diff --git a/cli-kex.c b/cli-kex.c
new file mode 100644
index 0000000..467ae23
--- /dev/null
+++ b/cli-kex.c
@@ -0,0 +1,298 @@
+/*
+ * Dropbear - a SSH2 server
+ * 
+ * Copyright (c) 2002-2004 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 "session.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 "random.h"
+#include "runopts.h"
+#include "signkey.h"
+
+
+static void checkhostkey(unsigned char* keyblob, unsigned int keybloblen);
+#define MAX_KNOWNHOSTS_LINE 4500
+
+void send_msg_kexdh_init() {
+
+	cli_ses.dh_e = (mp_int*)m_malloc(sizeof(mp_int));
+	cli_ses.dh_x = (mp_int*)m_malloc(sizeof(mp_int));
+	m_mp_init_multi(cli_ses.dh_e, cli_ses.dh_x, NULL);
+
+	gen_kexdh_vals(cli_ses.dh_e, cli_ses.dh_x);
+
+	CHECKCLEARTOWRITE();
+	buf_putbyte(ses.writepayload, SSH_MSG_KEXDH_INIT);
+	buf_putmpint(ses.writepayload, cli_ses.dh_e);
+	encrypt_packet();
+	ses.requirenext = SSH_MSG_KEXDH_REPLY;
+}
+
+/* Handle a diffie-hellman key exchange reply. */
+void recv_msg_kexdh_reply() {
+
+	DEF_MP_INT(dh_f);
+	sign_key *hostkey = NULL;
+	unsigned int type, keybloblen;
+	unsigned char* keyblob = NULL;
+
+
+	TRACE(("enter recv_msg_kexdh_reply"))
+
+	if (cli_ses.kex_state != KEXDH_INIT_SENT) {
+		dropbear_exit("Received out-of-order kexdhreply");
+	}
+	m_mp_init(&dh_f);
+	type = ses.newkeys->algo_hostkey;
+	TRACE(("type is %d", type))
+
+	hostkey = new_sign_key();
+	keybloblen = buf_getint(ses.payload);
+
+	keyblob = buf_getptr(ses.payload, keybloblen);
+	if (!ses.kexstate.donefirstkex) {
+		/* Only makes sense the first time */
+		checkhostkey(keyblob, keybloblen);
+	}
+
+	if (buf_get_pub_key(ses.payload, hostkey, &type) != DROPBEAR_SUCCESS) {
+		TRACE(("failed getting pubkey"))
+		dropbear_exit("Bad KEX packet");
+	}
+
+	if (buf_getmpint(ses.payload, &dh_f) != DROPBEAR_SUCCESS) {
+		TRACE(("failed getting mpint"))
+		dropbear_exit("Bad KEX packet");
+	}
+
+	kexdh_comb_key(cli_ses.dh_e, cli_ses.dh_x, &dh_f, hostkey);
+	mp_clear(&dh_f);
+	mp_clear_multi(cli_ses.dh_e, cli_ses.dh_x, NULL);
+	m_free(cli_ses.dh_e);
+	m_free(cli_ses.dh_x);
+
+	if (buf_verify(ses.payload, hostkey, ses.hash, SHA1_HASH_SIZE) 
+			!= DROPBEAR_SUCCESS) {
+		dropbear_exit("Bad hostkey signature");
+	}
+
+	sign_key_free(hostkey);
+	hostkey = NULL;
+
+	send_msg_newkeys();
+	ses.requirenext = SSH_MSG_NEWKEYS;
+	TRACE(("leave recv_msg_kexdh_init"))
+}
+
+static void ask_to_confirm(unsigned char* keyblob, unsigned int keybloblen) {
+
+	char* fp = NULL;
+	FILE *tty = NULL;
+	char response = 'z';
+
+	fp = sign_key_fingerprint(keyblob, keybloblen);
+	fprintf(stderr, "\nHost '%s' is not in the trusted hosts file.\n(fingerprint %s)\nDo you want to continue connecting? (y/n)\n", 
+			cli_opts.remotehost, 
+			fp);
+	m_free(fp);
+
+	tty = fopen(_PATH_TTY, "r");
+	if (tty) {
+		response = getc(tty);
+		fclose(tty);
+	} else {
+		response = getc(stdin);
+	}
+
+	if (response == 'y') {
+		return;
+	}
+
+	dropbear_exit("Didn't validate host key");
+}
+
+static void checkhostkey(unsigned char* keyblob, unsigned int keybloblen) {
+
+	char * filename = NULL;
+	FILE *hostsfile = NULL;
+	int readonly = 0;
+	struct passwd *pw = NULL;
+	char * homedir = NULL;
+	unsigned int hostlen, algolen;
+	unsigned long len;
+	const char *algoname = NULL;
+	buffer * line = NULL;
+	int ret;
+	
+	homedir = getenv("HOME");
+
+	if (!homedir) {
+		pw = getpwuid(getuid());
+		if (pw) {
+			homedir = pw->pw_dir;
+		}
+		pw = NULL;
+	}
+
+	if (homedir) {
+
+		len = strlen(homedir);
+		filename = m_malloc(len + 18); /* "/.ssh/known_hosts" and null-terminator*/
+
+		snprintf(filename, len+18, "%s/.ssh", homedir);
+		/* Check that ~/.ssh exists - easiest way is just to mkdir */
+		if (mkdir(filename, S_IRWXU) != 0) {
+			if (errno != EEXIST) {
+				dropbear_log(LOG_INFO, "Warning: failed creating %s/.ssh: %s",
+						homedir, strerror(errno));
+				TRACE(("mkdir didn't work: %s", strerror(errno)))
+				ask_to_confirm(keyblob, keybloblen);
+				goto out; /* only get here on success */
+			}
+		}
+
+		snprintf(filename, len+18, "%s/.ssh/known_hosts", homedir);
+		hostsfile = fopen(filename, "a+");
+		
+		if (hostsfile != NULL) {
+			fseek(hostsfile, 0, SEEK_SET);
+		} else {
+			/* We mightn't have been able to open it if it was read-only */
+			if (errno == EACCES || errno == EROFS) {
+					TRACE(("trying readonly: %s", strerror(errno)))
+					readonly = 1;
+					hostsfile = fopen(filename, "r");
+			}
+		}
+	}
+
+	if (hostsfile == NULL) {
+		TRACE(("hostsfile didn't open: %s", strerror(errno)))
+		dropbear_log(LOG_WARNING, "Failed to open %s/.ssh/known_hosts",
+				homedir);
+		ask_to_confirm(keyblob, keybloblen);
+		goto out; /* We only get here on success */
+	}
+
+	line = buf_new(MAX_KNOWNHOSTS_LINE);
+	hostlen = strlen(cli_opts.remotehost);
+	algoname = signkey_name_from_type(ses.newkeys->algo_hostkey, &algolen);
+
+	do {
+		if (buf_getline(line, hostsfile) == DROPBEAR_FAILURE) {
+			TRACE(("failed reading line: prob EOF"))
+			break;
+		}
+
+		/* The line is too short to be sensible */
+		/* "30" is 'enough to hold ssh-dss plus the spaces, ie so we don't
+		 * buf_getfoo() past the end and die horribly - the base64 parsing
+		 * code is what tiptoes up to the end nicely */
+		if (line->len < (hostlen+30) ) {
+			TRACE(("line is too short to be sensible"))
+			continue;
+		}
+
+		/* Compare hostnames */
+		if (strncmp(cli_opts.remotehost, buf_getptr(line, hostlen),
+					hostlen) != 0) {
+			TRACE(("hosts don't match"))
+			continue;
+		}
+
+		buf_incrpos(line, hostlen);
+		if (buf_getbyte(line) != ' ') {
+			/* there wasn't a space after the hostname, something dodgy */
+			TRACE(("missing space afte matching hostname"))
+			continue;
+		}
+
+		if ( strncmp(buf_getptr(line, algolen), algoname, algolen) != 0) {
+			TRACE(("algo doesn't match"))
+			continue;
+		}
+
+		buf_incrpos(line, algolen);
+		if (buf_getbyte(line) != ' ') {
+			TRACE(("missing space after algo"))
+			continue;
+		}
+
+		/* Now we're at the interesting hostkey */
+		ret = cmp_base64_key(keyblob, keybloblen, algoname, algolen, line);
+
+		if (ret == DROPBEAR_SUCCESS) {
+			/* Good matching key */
+			TRACE(("good matching key"))
+			goto out;
+		}
+
+		/* The keys didn't match. eep. */
+	} while (1); /* keep going 'til something happens */
+
+	/* Key doesn't exist yet */
+	ask_to_confirm(keyblob, keybloblen);
+
+	/* If we get here, they said yes */
+
+	if (readonly) {
+		TRACE(("readonly"))
+		goto out;
+	}
+
+	/* put the new entry in the file */
+	fseek(hostsfile, 0, SEEK_END); /* In case it wasn't opened append */
+	buf_setpos(line, 0);
+	buf_setlen(line, 0);
+	buf_putbytes(line, ses.remotehost, hostlen);
+	buf_putbyte(line, ' ');
+	buf_putbytes(line, algoname, algolen);
+	buf_putbyte(line, ' ');
+	len = line->size - line->pos;
+	TRACE(("keybloblen %d, len %d", keybloblen, len))
+	/* The only failure with base64 is buffer_overflow, but buf_getwriteptr
+	 * will die horribly in the case anyway */
+	base64_encode(keyblob, keybloblen, buf_getwriteptr(line, len), &len);
+	buf_incrwritepos(line, len);
+	buf_putbyte(line, '\n');
+	buf_setpos(line, 0);
+	fwrite(buf_getptr(line, line->len), line->len, 1, hostsfile);
+	/* We ignore errors, since there's not much we can do about them */
+
+out:
+	if (hostsfile != NULL) {
+		fclose(hostsfile);
+	}
+	m_free(filename);
+	if (line != NULL) {
+		buf_free(line);
+	}
+}