Backport tinc 1.1's str2net() function.

The old function could get confused by short-hand IPv6 notation (using ::)
and mistake them for MAC addresses. The new code is more strict; it will
correctly handle all short-hand addresses, and will return an error when
an address has trailing garbage instead of ignoring it.

diff --git a/src/subnet.c b/src/subnet.c
index dc30b01..0939d4c 100644 (file)
--- a/src/subnet.c
+++ b/src/subnet.c
@@ -205,55 +205,85 @@ void subnet_del(node_t *n, subnet_t *subnet) {
 /* Ascii representation of subnets */
 
 bool str2net(subnet_t *subnet, const char *subnetstr) {
-       int i, l;
-       uint16_t x[8];
+       char str[1024];
+       strncpy(str, subnetstr, sizeof(str));
+       str[sizeof(str) - 1] = 0;
+       int consumed;
+
        int weight = 10;
+       char *weight_separator = strchr(str, '#');
+
+       if(weight_separator) {
+               char *weight_str = weight_separator + 1;
 
-       if(sscanf(subnetstr, "%hu.%hu.%hu.%hu/%d#%d",
-                       &x[0], &x[1], &x[2], &x[3], &l, &weight) >= 5) {
-               if(l < 0 || l > 32) {
+               if(sscanf(weight_str, "%d%n", &weight, &consumed) < 1) {
                        return false;
                }
 
-               subnet->type = SUBNET_IPV4;
-               subnet->net.ipv4.prefixlength = l;
-               subnet->weight = weight;
+               if(weight_str[consumed]) {
+                       return false;
+               }
 
-               for(i = 0; i < 4; i++) {
-                       if(x[i] > 255) {
-                               return false;
-                       }
+               *weight_separator = 0;
+       }
 
-                       subnet->net.ipv4.address.x[i] = x[i];
+       int prefixlength = -1;
+       char *prefixlength_separator = strchr(str, '/');
+
+       if(prefixlength_separator) {
+               char *prefixlength_str = prefixlength_separator + 1;
+
+               if(sscanf(prefixlength_str, "%d%n", &prefixlength, &consumed) < 1) {
+                       return false;
                }
 
-               return true;
+               if(prefixlength_str[consumed]) {
+                       return false;
+               }
+
+               *prefixlength_separator = 0;
+
+               if(prefixlength < 0) {
+                       return false;
+               }
        }
 
-       if(sscanf(subnetstr, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx/%d#%d",
-                       &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7],
-                       &l, &weight) >= 9) {
-               if(l < 0 || l > 128) {
+       uint16_t x[8];
+
+       if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx%n", &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &consumed) >= 6 && !str[consumed]) {
+               /*
+                  Normally we should check that each part has two digits to prevent ambiguities.
+                  However, in old tinc versions net2str() will aggressively return MAC addresses with one-digit parts,
+                  so we have to accept them otherwise we would be unable to parse ADD_SUBNET messages.
+               */
+               if(prefixlength >= 0) {
                        return false;
                }
 
-               subnet->type = SUBNET_IPV6;
-               subnet->net.ipv6.prefixlength = l;
+               subnet->type = SUBNET_MAC;
                subnet->weight = weight;
 
-               for(i = 0; i < 8; i++) {
-                       subnet->net.ipv6.address.x[i] = htons(x[i]);
+               for(int i = 0; i < 6; i++) {
+                       subnet->net.mac.address.x[i] = x[i];
                }
 
                return true;
        }
 
-       if(sscanf(subnetstr, "%hu.%hu.%hu.%hu#%d", &x[0], &x[1], &x[2], &x[3], &weight) >= 4) {
+       if(sscanf(str, "%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !str[consumed]) {
+               if(prefixlength == -1) {
+                       prefixlength = 32;
+               }
+
+               if(prefixlength > 32) {
+                       return false;
+               }
+
                subnet->type = SUBNET_IPV4;
-               subnet->net.ipv4.prefixlength = 32;
+               subnet->net.ipv4.prefixlength = prefixlength;
                subnet->weight = weight;
 
-               for(i = 0; i < 4; i++) {
+               for(int i = 0; i < 4; i++) {
                        if(x[i] > 255) {
                                return false;
                        }
@@ -264,118 +294,73 @@ bool str2net(subnet_t *subnet, const char *subnetstr) {
                return true;
        }
 
-       if(sscanf(subnetstr, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx#%d",
-                       &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7], &weight) >= 8) {
-               subnet->type = SUBNET_IPV6;
-               subnet->net.ipv6.prefixlength = 128;
-               subnet->weight = weight;
+       /* IPv6 */
 
-               for(i = 0; i < 8; i++) {
-                       subnet->net.ipv6.address.x[i] = htons(x[i]);
-               }
+       char *last_colon = strrchr(str, ':');
 
-               return true;
-       }
-
-       if(sscanf(subnetstr, "%hx:%hx:%hx:%hx:%hx:%hx#%d",
-                       &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &weight) >= 6) {
-               subnet->type = SUBNET_MAC;
-               subnet->weight = weight;
-
-               for(i = 0; i < 6; i++) {
-                       subnet->net.mac.address.x[i] = x[i];
-               }
-
-               return true;
-       }
-
-       // IPv6 short form
-       if(strstr(subnetstr, "::")) {
-               const char *p;
-               char *q;
-               int colons = 0;
-
-               // Count number of colons
-               for(p = subnetstr; *p; p++)
-                       if(*p == ':') {
-                               colons++;
+       if(last_colon && sscanf(last_colon, ":%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !last_colon[consumed]) {
+               /* Dotted quad suffix notation, convert to standard IPv6 notation */
+               for(int i = 0; i < 4; i++)
+                       if(x[i] > 255) {
+                               return false;
                        }
 
-               if(colons > 7) {
-                       return false;
-               }
+               snprintf(last_colon, sizeof(str) - (last_colon - str), ":%02x%02x:%02x%02x", x[0], x[1], x[2], x[3]);
+       }
 
-               // Scan numbers before the double colon
-               p = subnetstr;
+       char *double_colon = strstr(str, "::");
 
-               for(i = 0; i < colons; i++) {
-                       if(*p == ':') {
-                               break;
-                       }
+       if(double_colon) {
+               /* Figure out how many zero groups we need to expand */
+               int zero_group_count = 8;
 
-                       x[i] = strtoul(p, &q, 0x10);
+               for(const char *cur = str; *cur; cur++)
+                       if(*cur != ':') {
+                               zero_group_count--;
 
-                       if(!q || p == q || *q != ':') {
-                               return false;
+                               while(cur[1] && cur[1] != ':') {
+                                       cur++;
+                               }
                        }
 
-                       p = ++q;
+               if(zero_group_count < 1) {
+                       return false;
                }
 
-               p++;
-               colons -= i;
+               /* Split the double colon in the middle to make room for zero groups */
+               double_colon++;
+               memmove(double_colon + (zero_group_count * 2 - 1), double_colon, strlen(double_colon) + 1);
 
-               if(!i) {
-                       p++;
-                       colons--;
+               /* Write zero groups in the resulting gap, overwriting the second colon */
+               for(int i = 0; i < zero_group_count; i++) {
+                       memcpy(&double_colon[i * 2], "0:", 2);
                }
 
-               if(!*p || *p == '/' || *p == '#') {
-                       colons--;
+               /* Remove any leading or trailing colons */
+               if(str[0] == ':') {
+                       memmove(&str[0], &str[1], strlen(&str[1]) + 1);
                }
 
-               // Fill in the blanks
-               for(; i < 8 - colons; i++) {
-                       x[i] = 0;
-               }
-
-               // Scan the remaining numbers
-               for(; i < 8; i++) {
-                       x[i] = strtoul(p, &q, 0x10);
-
-                       if(!q || p == q) {
-                               return false;
-                       }
-
-                       if(i == 7) {
-                               p = q;
-                               break;
-                       }
-
-                       if(*q != ':') {
-                               return false;
-                       }
-
-                       p = ++q;
+               if(str[strlen(str) - 1] == ':') {
+                       str[strlen(str) - 1] = 0;
                }
+       }
 
-               l = 128;
-
-               if(*p == '/') {
-                       sscanf(p, "/%d#%d", &l, &weight);
-               } else if(*p == '#') {
-                       sscanf(p, "#%d", &weight);
+       if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx%n",
+                       &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7], &consumed) >= 8 && !str[consumed]) {
+               if(prefixlength == -1) {
+                       prefixlength = 128;
                }
 
-               if(l < 0 || l > 128) {
+               if(prefixlength > 128) {
                        return false;
                }
 
                subnet->type = SUBNET_IPV6;
-               subnet->net.ipv6.prefixlength = l;
+               subnet->net.ipv6.prefixlength = prefixlength;
                subnet->weight = weight;
 
-               for(i = 0; i < 8; i++) {
+               for(int i = 0; i < 8; i++) {
                        subnet->net.ipv6.address.x[i] = htons(x[i]);
                }