Add client support for multiple domain names.

For fun, support multiple domain names:

    sdt sshdns.a.example.com sshdns.b.example.com \
        sshdns.a.example1.com sshdns.b.example1.com

Update server to check a list of domain names. The server checks domain
names to prevent responding to random queries/scans. This can be disabled
by using the keyword "any" as a domain name, i.e.:

    sods any

sdt/sdt.c

@@ -40,6 +40,7 @@ main(int argc, char *argv[])
     pid_t pid = 0;
     int nd = 0;
     int ch = 0;
+    int di = 0;
 
     IS_NULL(ss = (SDT_STATE *)calloc(1, sizeof(SDT_STATE)));
 
@@ -57,7 +58,9 @@ main(int argc, char *argv[])
     ss->type = ns_t_txt;
     ss->verbose_lines = 100;
 
-    while ( (ch = getopt(argc, argv, "A:B:b:dF:hM:m:R:r:S:s:T:t:vx:")) != -1) {
+    ss->dname_next = &sdt_dns_dn_roundrobin;
+
+    while ( (ch = getopt(argc, argv, "A:B:b:dF:hM:m:n:R:r:S:s:T:t:vx:")) != -1) {
         switch (ch) {
             case 'A':	/* alarm, delay buf */
                 ss->delay = (u_int32_t)atoi(optarg);
@@ -80,6 +83,14 @@ main(int argc, char *argv[])
             case 'm':
                 ss->sleep = (u_int32_t)atoi(optarg);
                 break;
+            case 'n':   /* strategy for shuffling domain name list */
+                if (strcasecmp(optarg, "roundrobin") == 0)
+                    ss->dname_next = &sdt_dns_dn_roundrobin;
+                else if (strcasecmp(optarg, "random") == 0)
+                    ss->dname_next = &sdt_dns_dn_random;
+                else
+                    usage(ss);
+                break;
             case 'R':   /* Retry lookup */
                 sdt_dns_setopt(SDT_RES_RETRY, (u_int32_t)atoi(optarg));
                 break;
@@ -129,10 +140,16 @@ main(int argc, char *argv[])
     argc -= optind;
     argv += optind;
 
-    if ( (argc != 1) || (strlen(argv[0]) > NS_MAXCDNAME - 1))
+    if ( (argc == 0) || (argc >= MAXDNAMELIST))
         usage(ss);
 
-    IS_NULL(ss->dname = strdup(argv[0]));
+    ss->dname_max = argc;
+    IS_NULL(ss->dname = (char **)calloc(argc, 1));
+    for ( di = 0; di < argc; di++) {
+        if (strlen(argv[di]) > NS_MAXCDNAME - 1)
+            usage(ss);
+        IS_NULL(ss->dname[di] = strdup(argv[di]));
+    }
 
     IS_ERR(nd = open("/dev/null", O_RDWR, 0));
 
@@ -390,8 +407,9 @@ usage(SDT_STATE *ss)
     (void)fprintf(stderr, "-F <num>\tFast start, number of small packets to pass w/out buffering (0 to disable) [default: %d]\n", ss->faststart);
     (void)fprintf(stderr, "-M\tMaximum number of polling query failures [default: %d]\n", ss->maxpollfail);
     (void)fprintf(stderr, "-m\tMinimum time to sleep between nameserver queries [default: %d us]\n", ss->sleep);
+    (void)fprintf(stderr, "-n <roundrobin|random>\tStrategy for shuffling domain names [default: roundrobin]\n");
     (void)fprintf(stderr, "-R <number>\tNumber of retries for lookup\n");
-    (void)fprintf(stderr, "-r\tNameserver (or keyword: random, opendns, verizon, speakeasy)\n");
+    (void)fprintf(stderr, "-r\tNameserver (or keyword: random, opendns, verizon, speakeasy, google)\n");
     (void)fprintf(stderr, "-S [rotate|blast]\tResolver strategy\n");
     (void)fprintf(stderr, "-T <number>\tUse TCP [0 = new connection for each request, 1 = pipeline requests]\n");
     (void)fprintf(stderr, "-t <DNS type>\tTXT, CNAME [Default = TXT]\n");

sdt/sdt.h

@@ -98,6 +98,8 @@
 #define MAXBACKOFF  3000    /* 3000 * 20000  = 60,000,000 (1/minute) */
 #define MAXPOLLFAIL  10      /* Number of TXT record failures before giving up */
 
+#define MAXDNAMELIST 256    /* arbitrary cutoff for number of domains */
+
 
 typedef union _SDT_ID {
     struct {
@@ -109,7 +111,9 @@ typedef union _SDT_ID {
 } SDT_ID;
 
 typedef struct _SDT_STATE {
-    char        *dname;
+    char        **dname;
+    int         dname_max;
+    int         dname_iterator;
     SDT_ID      sess;   
     size_t      sum;
     size_t      sum_up;
@@ -125,6 +129,8 @@ typedef struct _SDT_STATE {
     pid_t       child;
     int         verbose;
     int         verbose_lines;
+
+    char *(*dname_next)(void *state);
 } SDT_STATE;
 
 /* Resolver options */
@@ -151,10 +157,13 @@ int sdt_dns_parsens(SDT_STATE *ss, char *buf);
 int sdt_dns_A(SDT_STATE *ss, char *buf, ssize_t n);
 char *sdt_dns_poll(SDT_STATE *ss, size_t *len);
 char *sdt_dns_parse(SDT_STATE *ss, char *pkt, int *pktlen);
-char * sdt_dns_dec_CNAME(SDT_STATE *ss, u_char *data, u_int16_t *n);
-char * sdt_dns_dec_TXT(SDT_STATE *ss, u_char *data, u_int16_t *n);
-char * sdt_dns_dec_NULL(SDT_STATE *ss, u_char *data, u_int16_t *n);
+char *sdt_dns_dec_CNAME(SDT_STATE *ss, u_char *data, u_int16_t *n);
+char *sdt_dns_dec_TXT(SDT_STATE *ss, u_char *data, u_int16_t *n);
+char *sdt_dns_dec_NULL(SDT_STATE *ss, u_char *data, u_int16_t *n);
 void sdt_dns_print_servers(SDT_STATE *ss);
+char *sdt_dns_dn_roundrobin(void *state);
+char *sdt_dns_dn_random(void *state);
+
 
 void sdt_rand_init(void);
 #ifndef HAVE_ARC4RANDOM

sdt/sdt_dns.c

@@ -136,7 +136,7 @@ sdt_dns_A(SDT_STATE *ss, char *buf, ssize_t n)
      *  $temp_payload.$nonce-$sum_up.id-$id.up.$extension
      */
     (void)snprintf(query, sizeof(query), "%s.%u-%u.id-%u.up.%s",
-            dn, nonce, (u_int32_t)ss->sum_up, htonl(ss->sess.id), ss->dname);
+            dn, nonce, (u_int32_t)ss->sum_up, htonl(ss->sess.id), ss->dname_next(ss));
 
     VERBOSE(2, "A:%s\n", query);
     if (res_search(query, ns_c_in, ns_t_a, (u_char *)&pkt, sizeof(pkt)) < 0) {
@@ -166,7 +166,7 @@ sdt_dns_poll(SDT_STATE *ss, size_t *len)
      *  $sum-$nonce.id-$id.down.$extension
      */
     (void)snprintf(query, sizeof(query), "%u-%u.id-%u.down.%s",
-            (u_int32_t)ss->sum, nonce, htonl(ss->sess.id), ss->dname);
+            (u_int32_t)ss->sum, nonce, htonl(ss->sess.id), ss->dname_next(ss));
 
     VERBOSE(2, "POLL:%s\n", query);
 
@@ -415,3 +415,21 @@ sdt_dns_print_servers(SDT_STATE *ss)
     }
 }
 
+
+/* Strategies for iterating through multiple
+ * domain names */
+    char *
+sdt_dns_dn_roundrobin(void *state)
+{
+    SDT_STATE *ss = state;
+    return (ss->dname[ss->dname_iterator++ % ss->dname_max]);
+}
+
+    char *
+sdt_dns_dn_random(void *state)
+{
+    SDT_STATE *ss = state;
+    return (ss->dname[sdt_rand() % ss->dname_max]);
+}
+
+

sods/sods.c

@@ -39,6 +39,7 @@ main (int argc, char *argv[])
     SDS_STATE *ss = NULL;
 
     int ch = 0;
+    int di = 0;
 
     IS_NULL(ss = (SDS_STATE *)calloc(1, sizeof(SDS_STATE)));
 
@@ -102,10 +103,16 @@ main (int argc, char *argv[])
     argc -= optind;
     argv += optind;
 
-    if ( (argc != 1) || (strlen(argv[0]) > NS_MAXDNAME - 1))
+    if ( (argc == 0) || (argc >= MAXDNAMELIST))
         usage(ss);
 
-    IS_NULL(ss->dn = strdup(argv[0]));
+    ss->dn_max = argc;
+    IS_NULL(ss->dn = (char **)calloc(argc, 1));
+    for ( di = 0; di < argc; di++) {
+        if (strlen(argv[di]) > NS_MAXCDNAME - 1)
+            usage(ss);
+            IS_NULL(ss->dn[di] = strdup(argv[di]));
+    }
 
     if (ss->fwd == NULL)
         (void)sds_parse_forward(ss, "127.0.0.1:22");

sods/sods.h

@@ -80,7 +80,8 @@
 #define BUFLEN          110
 #define NS_TXTREC       65535   /* see http://www.zeroconf.org/Rendezvous/txtrecords.html */
 
-#define MAXFWDS  32     /* Maximum number of allowed forwarders */
+#define MAXFWDS         32      /* Maximum number of allowed forwarders */
+#define MAXDNAMELIST    256     /* Maximum number of domain names */
 
 typedef struct _SDS_FWD {
     u_int8_t    sess;           /* Unused */
@@ -89,7 +90,8 @@ typedef struct _SDS_FWD {
 
 typedef struct _SDS_STATE {
     int s;
-    char *dn;
+    char **dn;
+    int dn_max;
     char *func;                     /* sshdns, socket ... */
     SDS_FWD *fwd;
     size_t fwds;                    /* number of forwarded sessions */

sods/sods_dns.c

@@ -408,6 +408,7 @@ sds_dns_packet(SDS_PKT *pkt, void *data, size_t len)
 sds_dns_checkdn(SDS_STATE *ss, char *domain)
 {
     char *p = NULL;
+    int i = 0;
 
     p = strchr(domain, '.');
     *p++ = '\0';
@@ -417,11 +418,15 @@ sds_dns_checkdn(SDS_STATE *ss, char *domain)
         return (-1);
 #endif
 
-    if (strncmp(ss->dn, p, strlen(ss->dn)+1) != 0) {
-        VERBOSE(1, "rejecting request for domain: %s\n", p);
-        return (-1);
+    if (strcmp(ss->dn[0], "any") == 0)
+        return (0);
+
+    for ( i = 0; i < ss->dn_max; i++) {
+        if (strncmp(ss->dn[i], p, strlen(ss->dn[i])+1) == 0)
+            return (0);
     }
 
-    return (0);
+    VERBOSE(1, "rejecting request for domain: %s\n", p);
+    return (-1);
 }