OpenWrt – Rev 4
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/* This bit implements a simple API for using the SRP library over sockets. */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include "t_defines.h"
#include "t_pwd.h"
#include "t_server.h"
#include "t_client.h"
#include "tinysrp.h"
#ifndef MSG_WAITALL
#ifdef linux
#define MSG_WAITALL 0x100 /* somehow not defined on my box */
#endif
#endif
/* This is called by the client with a connected socket, username, and
passphrase. pass can be NULL in which case the user is queried. */
int tsrp_client_authenticate(int s, char *user, char *pass, TSRP_SESSION *tsrp)
{
int i, index;
unsigned char username[MAXUSERLEN + 1], sbuf[MAXSALTLEN];
unsigned char msgbuf[MAXPARAMLEN + 1], bbuf[MAXPARAMLEN];
unsigned char passbuf[128], *skey;
struct t_client *tc;
struct t_preconf *tcp; /* @@@ should go away */
struct t_num salt, *A, B;
/* Send the username. */
i = strlen(user);
if (i > MAXUSERLEN) {
i = MAXUSERLEN;
}
msgbuf[0] = i;
memcpy(msgbuf + 1, user, i);
if (send(s, msgbuf, i + 1, 0) < 0) {
return 0;
}
memcpy(username, user, i);
username[i] = '\0';
/* Get the prime index and salt. */
i = recv(s, msgbuf, 2, MSG_WAITALL);
if (i <= 0) {
return 0;
}
index = msgbuf[0];
if (index <= 0 || index > t_getprecount()) {
return 0;
}
tcp = t_getpreparam(index - 1);
salt.len = msgbuf[1];
if (salt.len > MAXSALTLEN) {
return 0;
}
salt.data = sbuf;
i = recv(s, sbuf, salt.len, MSG_WAITALL);
if (i <= 0) {
return 0;
}
/* @@@ t_clientopen() needs a variant that takes the index */
tc = t_clientopen(username, &tcp->modulus, &tcp->generator, &salt);
if (tc == NULL) {
return 0;
}
/* Calculate A and send it to the server. */
A = t_clientgenexp(tc);
msgbuf[0] = A->len - 1; /* len is max 256 */
memcpy(msgbuf + 1, A->data, A->len);
if (send(s, msgbuf, A->len + 1, 0) < 0) {
return 0;
}
/* Ask the user for the passphrase. */
if (pass == NULL) {
t_getpass(passbuf, sizeof(passbuf), "Enter password:");
pass = passbuf;
}
t_clientpasswd(tc, pass);
/* Get B from the server. */
i = recv(s, msgbuf, 1, 0);
if (i <= 0) {
return 0;
}
B.len = msgbuf[0] + 1;
B.data = bbuf;
i = recv(s, bbuf, B.len, MSG_WAITALL);
if (i <= 0) {
return 0;
}
/* Compute the session key. */
skey = t_clientgetkey(tc, &B);
if (skey == NULL) {
return 0;
}
/* Send the response. */
if (send(s, t_clientresponse(tc), RESPONSE_LEN, 0) < 0) {
return 0;
}
/* Get the server's response. */
i = recv(s, msgbuf, RESPONSE_LEN, MSG_WAITALL);
if (i <= 0) {
return 0;
}
if (t_clientverify(tc, msgbuf) != 0) {
return 0;
}
/* All done. Now copy the key and clean up. */
if (tsrp) {
memcpy(tsrp->username, username, strlen(username) + 1);
memcpy(tsrp->key, skey, SESSION_KEY_LEN);
}
t_clientclose(tc);
return 1;
}
/* This is called by the server with a connected socket. */
int tsrp_server_authenticate(int s, TSRP_SESSION *tsrp)
{
int i, j;
unsigned char username[MAXUSERLEN], *skey;
unsigned char msgbuf[MAXPARAMLEN + 1], abuf[MAXPARAMLEN];
struct t_server *ts;
struct t_num A, *B;
/* Get the username. */
i = recv(s, msgbuf, 1, 0);
if (i <= 0) {
return 0;
}
j = msgbuf[0];
i = recv(s, username, j, MSG_WAITALL);
if (i <= 0) {
return 0;
}
username[j] = '\0';
ts = t_serveropen(username);
if (ts == NULL) {
return 0;
}
/* Send the prime index and the salt. */
msgbuf[0] = ts->index; /* max 256 primes... */
i = ts->s.len;
msgbuf[1] = i;
memcpy(msgbuf + 2, ts->s.data, i);
if (send(s, msgbuf, i + 2, 0) < 0) {
return 0;
}
/* Calculate B while we're waiting. */
B = t_servergenexp(ts);
/* Get A from the client. */
i = recv(s, msgbuf, 1, 0);
if (i <= 0) {
return 0;
}
A.len = msgbuf[0] + 1;
A.data = abuf;
i = recv(s, abuf, A.len, MSG_WAITALL);
if (i <= 0) {
return 0;
}
/* Now send B. */
msgbuf[0] = B->len - 1;
memcpy(msgbuf + 1, B->data, B->len);
if (send(s, msgbuf, B->len + 1, 0) < 0) {
return 0;
}
/* Calculate the session key while we're waiting. */
skey = t_servergetkey(ts, &A);
if (skey == NULL) {
return 0;
}
/* Get the response from the client. */
i = recv(s, msgbuf, RESPONSE_LEN, MSG_WAITALL);
if (i <= 0) {
return 0;
}
if (t_serververify(ts, msgbuf) != 0) {
return 0;
}
/* Client authenticated. Now authenticate ourselves to the client. */
if (send(s, t_serverresponse(ts), RESPONSE_LEN, 0) < 0) {
return 0;
}
/* Copy the key and clean up. */
if (tsrp) {
memcpy(tsrp->username, username, strlen(username) + 1);
memcpy(tsrp->key, skey, SESSION_KEY_LEN);
}
t_serverclose(ts);
return 1;
}