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265 lines
8.7 KiB
265 lines
8.7 KiB
/* kex.c is used well, in key exchange :-) */
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/*
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Copyright 2003 Aris Adamantiadis
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This file is part of the SSH Library
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The SSH Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The SSH Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the SSH Library; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Steet, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include <string.h>
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#include <stdlib.h>
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#include "priv.h"
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#include "ssh2.h"
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#ifdef HAVE_OPENSSL_BLOWFISH_H
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#define BLOWFISH "blowfish-cbc"
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#else
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#define BLOWFISH ""
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#endif
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#ifdef HAVE_OPENSSL_AES_H
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#define AES "aes256-cbc,aes192-cbc,aes128-cbc,"
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#else
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#define AES ""
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#endif
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#ifdef HAVE_LIBZ
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#define ZLIB "none,zlib"
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#else
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#define ZLIB "none"
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#endif
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char *default_methods[]={
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"diffie-hellman-group1-sha1","ssh-dss,ssh-rsa",AES BLOWFISH, AES BLOWFISH,
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"hmac-sha1","hmac-sha1","none","none","","",NULL };
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char *supported_methods[]={
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"diffie-hellman-group1-sha1","ssh-dss,ssh-rsa",AES BLOWFISH,AES BLOWFISH,
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"hmac-sha1","hmac-sha1",ZLIB,ZLIB,"","",NULL };
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/* descriptions of the key exchange packet */
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char *ssh_kex_nums[]={
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"kex algos","server host key algo","encryption client->server","encryption server->client",
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"mac algo client->server","mac algo server->client","compression algo client->server",
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"compression algo server->client","languages client->server","languages server->client",NULL};
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/* tokenize will return a token of strings delimited by ",". the first element has to be freed */
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static char **tokenize(char *chain){
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char **tokens;
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int n=1;
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int i=0;
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char *ptr=chain=strdup(chain);
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while(*ptr){
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if(*ptr==','){
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n++;
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*ptr=0;
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}
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ptr++;
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}
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/* now n contains the number of tokens, the first possibly empty if the list was empty too e.g. "" */
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tokens=malloc(sizeof(char *) * (n+1) ); /* +1 for the null */
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ptr=chain;
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for(i=0;i<n;i++){
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tokens[i]=ptr;
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while(*ptr)
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ptr++; /* find a zero */
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ptr++; /* then go one step further */
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}
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tokens[i]=NULL;
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return tokens;
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}
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/* same as tokenize(), but with spaces instead of ',' */
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char **space_tokenize(char *chain){
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char **tokens;
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int n=1;
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int i=0;
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char *ptr=chain=strdup(chain);
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while(*ptr==' ')
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++ptr; /* skip initial spaces */
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while(*ptr){
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if(*ptr==' '){
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n++; /* count one token per word */
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*ptr=0;
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while(*(ptr+1)==' '){ /* don't count if the tokens have more than 2 spaces */
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*(ptr++)=0;
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}
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}
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ptr++;
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}
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/* now n contains the number of tokens, the first possibly empty if the list was empty too e.g. "" */
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tokens=malloc(sizeof(char *) * (n+1) ); /* +1 for the null */
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ptr=chain; /* we don't pass the initial spaces because the "chain" pointer is needed by the caller */
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/* function to free the tokens. */
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for(i=0;i<n;i++){
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tokens[i]=ptr;
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if(i!=n-1){
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while(*ptr)
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ptr++; /* find a zero */
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while(!*(ptr+1))
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++ptr; /* if the zero is followed by other zeros, go through them */
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ptr++; /* then go one step further */
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}
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}
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tokens[i]=NULL;
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return tokens;
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}
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/* find_matching gets 2 parameters : a list of available objects (in_d), separated by colons,*/
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/* and a list of prefered objects (what_d) */
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/* it will return a strduped pointer on the first prefered object found in the available objects list */
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static char *find_matching(char *in_d, char *what_d){
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char ** tok_in, **tok_what;
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int i_in, i_what;
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char *ret;
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if( ! (in_d && what_d))
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return NULL; /* don't deal with null args */
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ssh_say(3,"find_matching(\"%s\",\"%s\") = ",in_d,what_d);
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tok_in=tokenize(in_d);
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tok_what=tokenize(what_d);
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for(i_in=0; tok_in[i_in]; ++i_in){
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for(i_what=0; tok_what[i_what] ; ++i_what){
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if(!strcmp(tok_in[i_in],tok_what[i_what])){
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/* match */
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ssh_say(3,"\"%s\"\n",tok_in[i_in]);
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ret=strdup(tok_in[i_in]);
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/* free the tokens */
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free(tok_in[0]);
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free(tok_what[0]);
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free(tok_in);
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free(tok_what);
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return ret;
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}
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}
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}
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ssh_say(3,"NULL\n");
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free(tok_in[0]);
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free(tok_what[0]);
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free(tok_in);
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free(tok_what);
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return NULL;
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}
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int ssh_get_kex(SSH_SESSION *session,int server_kex ){
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STRING *str;
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char *strings[10];
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int i;
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if(packet_wait(session,SSH2_MSG_KEXINIT,1))
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return -1;
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if(buffer_get_data(session->in_buffer,session->server_kex.cookie,16)!=16){
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ssh_set_error((session->connected?session:NULL),SSH_FATAL,"get_kex(): no cookie in packet");
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return -1;
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}
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hashbufin_add_cookie(session,session->server_kex.cookie);
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memset(strings,0,sizeof(char *)*10);
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for(i=0;i<10;++i){
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str=buffer_get_ssh_string(session->in_buffer);
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if(!str)
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break;
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if(str){
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buffer_add_ssh_string(session->in_hashbuf,str);
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strings[i]=string_to_char(str);
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free(str);
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} else
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strings[i]=NULL;
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}
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/* copy the server kex info into an array of strings */
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if(server_kex){
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session->client_kex.methods=malloc( 10 * sizeof(char **));
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for(i=0;i<10;++i)
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session->client_kex.methods[i]=strings[i];
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} else { /* client */
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session->server_kex.methods=malloc( 10 * sizeof(char **));
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for(i=0;i<10;++i)
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session->server_kex.methods[i]=strings[i];
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}
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return 0;
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}
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void list_kex(KEX *kex){
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int i=0;
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#ifdef DEBUG_CRYPTO
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ssh_print_hexa("session cookie",kex->cookie,16);
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#endif
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for(i=0;i<10;i++){
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ssh_say(2,"%s : %s\n",ssh_kex_nums[i],kex->methods[i]);
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}
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}
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/* set_kex basicaly look at the option structure of the session and set the output kex message */
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/* it must be aware of the server kex message */
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/* it can fail if option is null, not any user specified kex method matches the server one, if not any default kex matches */
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int set_kex(SSH_SESSION *session){
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KEX *server = &session->server_kex;
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KEX *client=&session->client_kex;
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SSH_OPTIONS *options=session->options;
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int i;
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char *wanted;
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/* the client might ask for a specific cookie to be sent. useful for server debugging */
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if(options->wanted_cookie)
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memcpy(client->cookie,options->wanted_cookie,16);
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else
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ssh_get_random(client->cookie,16);
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client->methods=malloc(10 * sizeof(char **));
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memset(client->methods,0,10*sizeof(char **));
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for (i=0;i<10;i++){
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if(!(wanted=options->wanted_methods[i]))
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wanted=default_methods[i];
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client->methods[i]=find_matching(server->methods[i],wanted);
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if(!client->methods[i] && i < KEX_LANG_C_S){
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ssh_set_error((session->connected?session:NULL),SSH_FATAL,"kex error : did not find one of algos %s in list %s for %s",
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wanted,server->methods[i],ssh_kex_nums[i]);
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return -1;
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} else {
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if(i>=KEX_LANG_C_S && !client->methods[i])
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client->methods[i]=strdup(""); /* we can safely do that for languages */
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}
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}
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return 0;
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}
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/* this function only sends the predefined set of kex methods */
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void send_kex(SSH_SESSION *session, int server_kex){
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STRING *str;
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int i=0;
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KEX *kex=(server_kex ? &session->server_kex : &session->client_kex);
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packet_clear_out(session);
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buffer_add_u8(session->out_buffer,SSH2_MSG_KEXINIT);
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buffer_add_data(session->out_buffer,kex->cookie,16);
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hashbufout_add_cookie(session);
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list_kex(kex);
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for(i=0;i<10;i++){
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str=string_from_char(kex->methods[i]);
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buffer_add_ssh_string(session->out_hashbuf,str);
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buffer_add_ssh_string(session->out_buffer,str);
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free(str);
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}
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i=0;
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buffer_add_u8(session->out_buffer,0);
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buffer_add_u32(session->out_buffer,0);
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packet_send(session);
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}
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/* returns 1 if at least one of the name algos is in the default algorithms table */
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int verify_existing_algo(int algo, char *name){
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char *ptr;
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if(algo>9 || algo <0)
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return -1;
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ptr=find_matching(supported_methods[algo],name);
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if(ptr){
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free(ptr);
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return 1;
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}
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return 0;
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}
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