From 3d730a40a42d9b238da8725438a612296dea3860 Mon Sep 17 00:00:00 2001 From: Etienne Dechamps Date: Sat, 5 Jul 2014 18:05:55 +0100 Subject: [PATCH] Rewrite, fix and improve str2net(). This is a complete rewrite of the str2net() function. Besides refactoring duplicate code, this new code brings the following fixes and improvements: - Fixes handling of leading/trailing double colon in IPv6 addresses. For example, with the previous code the address 2001:0db8:85a3:0000:0000:8a2e:0370:: is interpreted as a MAC address, and ::0db8:85a3:0000:0000:8a2e:0370:7334 is rejected. - Catches more invalid cases, such as garbage at the end of the string. - Adds support for dotted quad notation in IPv6 (e.g. ::1.2.3.4). See RFC 4291, section 2.2 for details on the textual format of IPv6 addresses. --- src/subnet_parse.c | 191 +++++++++++++++++++-------------------------- 1 file changed, 80 insertions(+), 111 deletions(-) diff --git a/src/subnet_parse.c b/src/subnet_parse.c index f9801800..35f078af 100644 --- a/src/subnet_parse.c +++ b/src/subnet_parse.c @@ -181,150 +181,119 @@ int subnet_compare(const subnet_t *a, const subnet_t *b) { /* Ascii representation of subnets */ bool str2net(subnet_t *subnet, const char *subnetstr) { - int i, l; - uint16_t x[8]; - int weight = 10; + char str[1024]; + strncpy(str, subnetstr, sizeof(str)); + int consumed; - 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) + int weight = 10; + char *weight_separator = strchr(str, '#'); + if (weight_separator) { + char *weight_str = weight_separator + 1; + if (sscanf(weight_str, "%d%n", &weight, &consumed) < 1) return false; + if (weight_str[consumed]) + return false; + *weight_separator = 0; + } - subnet->type = SUBNET_IPV4; - subnet->net.ipv4.prefixlength = l; - subnet->weight = weight; - - for(int i = 0; i < 4; i++) { - if(x[i] > 255) - return false; - 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; + if (prefixlength_str[consumed]) + return false; + *prefixlength_separator = 0; - return true; + 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 agressively 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++) { - if(x[i] > 255) + for(int i = 0; i < 4; i++) { + if (x[i] > 255) return false; subnet->net.ipv4.address.x[i] = x[i]; } - - 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; - - for(i = 0; i < 8; i++) - subnet->net.ipv6.address.x[i] = htons(x[i]); - 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]; + /* IPv6 */ - return true; + char* last_colon = strrchr(str, ':'); + 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; + sprintf(last_colon, ":%02hx%02hx:%02hx%02hx", x[0], x[1], x[2], x[3]); } - // 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(colons > 7) + char* double_colon = strstr(str, "::"); + if (double_colon) { + /* Figure out how many zero groups we need to expand */ + int zero_group_count = 8; + for (const char* cur = str; *cur; *cur && cur++) + if (*cur != ':') { + zero_group_count--; + for (; *cur && *cur != ':'; cur++); + } + if (zero_group_count < 1) return false; - // Scan numbers before the double colon - p = subnetstr; - for(i = 0; i < colons; i++) { - if(*p == ':') - break; - x[i] = strtoul(p, &q, 0x10); - if(!q || p == q || *q != ':') - return false; - p = ++q; - } - - p++; - colons -= i; - if(!i) { - p++; - colons--; - } - - if(!*p || *p == '/' || *p == '#') - colons--; - - // Fill in the blanks - for(; i < 8 - colons; i++) - x[i] = 0; + /* 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); - // 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; - } + /* 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); - l = 128; - if(*p == '/') - sscanf(p, "/%d#%d", &l, &weight); - else if(*p == '#') - sscanf(p, "#%d", &weight); + /* Remove any leading or trailing colons */ + if (str[0] == ':') + memmove(&str[0], &str[1], strlen(&str[1]) + 1); + if (str[strlen(str) - 1] == ':') + str[strlen(str) - 1] = 0; + } - if(l < 0 || l > 128) + 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 (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]); - return true; } -- 2.20.1