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Diffstat (limited to 'src/app/config/resolve_addr.c')
| -rw-r--r-- | src/app/config/resolve_addr.c | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/src/app/config/resolve_addr.c b/src/app/config/resolve_addr.c new file mode 100644 index 0000000000..9d1a8e0260 --- /dev/null +++ b/src/app/config/resolve_addr.c @@ -0,0 +1,314 @@ +/* Copyright (c) 2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file resolve_addr.c + * \brief Implement resolving address functions + **/ + +#define RESOLVE_ADDR_PRIVATE + +#include "app/config/config.h" +#include "app/config/resolve_addr.h" + +#include "core/mainloop/mainloop.h" + +#include "feature/control/control_events.h" + +#include "lib/net/gethostname.h" +#include "lib/net/resolve.h" + +/** Last value actually set by resolve_my_address. */ +static uint32_t last_resolved_addr = 0; + +/** Accessor for last_resolved_addr from outside this file. */ +uint32_t +get_last_resolved_addr(void) +{ + return last_resolved_addr; +} + +/** Reset last_resolved_addr from outside this file. */ +void +reset_last_resolved_addr(void) +{ + last_resolved_addr = 0; +} + +/** + * Attempt getting our non-local (as judged by tor_addr_is_internal() + * function) IP address using following techniques, listed in + * order from best (most desirable, try first) to worst (least + * desirable, try if everything else fails). + * + * First, attempt using <b>options-\>Address</b> to get our + * non-local IP address. + * + * If <b>options-\>Address</b> represents a non-local IP address, + * consider it ours. + * + * If <b>options-\>Address</b> is a DNS name that resolves to + * a non-local IP address, consider this IP address ours. + * + * If <b>options-\>Address</b> is NULL, fall back to getting local + * hostname and using it in above-described ways to try and + * get our IP address. + * + * In case local hostname cannot be resolved to a non-local IP + * address, try getting an IP address of network interface + * in hopes it will be non-local one. + * + * Fail if one or more of the following is true: + * - DNS name in <b>options-\>Address</b> cannot be resolved. + * - <b>options-\>Address</b> is a local host address. + * - Attempt at getting local hostname fails. + * - Attempt at getting network interface address fails. + * + * Return 0 if all is well, or -1 if we can't find a suitable + * public IP address. + * + * If we are returning 0: + * - Put our public IP address (in host order) into *<b>addr_out</b>. + * - If <b>method_out</b> is non-NULL, set *<b>method_out</b> to a static + * string describing how we arrived at our answer. + * - "CONFIGURED" - parsed from IP address string in + * <b>options-\>Address</b> + * - "RESOLVED" - resolved from DNS name in <b>options-\>Address</b> + * - "GETHOSTNAME" - resolved from a local hostname. + * - "INTERFACE" - retrieved from a network interface. + * - If <b>hostname_out</b> is non-NULL, and we resolved a hostname to + * get our address, set *<b>hostname_out</b> to a newly allocated string + * holding that hostname. (If we didn't get our address by resolving a + * hostname, set *<b>hostname_out</b> to NULL.) + * + * XXXX ipv6 + */ +int +resolve_my_address(int warn_severity, const or_options_t *options, + uint32_t *addr_out, + const char **method_out, char **hostname_out) +{ + struct in_addr in; + uint32_t addr; /* host order */ + char hostname[256]; + const char *method_used; + const char *hostname_used; + int explicit_ip=1; + int explicit_hostname=1; + int from_interface=0; + char *addr_string = NULL; + const char *address = options->Address; + int notice_severity = warn_severity <= LOG_NOTICE ? + LOG_NOTICE : warn_severity; + + tor_addr_t myaddr; + tor_assert(addr_out); + + /* + * Step one: Fill in 'hostname' to be our best guess. + */ + + if (address && *address) { + strlcpy(hostname, address, sizeof(hostname)); + log_debug(LD_CONFIG, "Trying configured Address '%s' as local hostname", + hostname); + } else { /* then we need to guess our address */ + explicit_ip = 0; /* it's implicit */ + explicit_hostname = 0; /* it's implicit */ + + if (tor_gethostname(hostname, sizeof(hostname)) < 0) { + log_fn(warn_severity, LD_NET,"Error obtaining local hostname"); + return -1; + } + log_debug(LD_CONFIG, "Guessed local host name as '%s'", hostname); + } + + /* + * Step two: Now that we know 'hostname', parse it or resolve it. If + * it doesn't parse or resolve, look at the interface address. Set 'addr' + * to be our (host-order) 32-bit answer. + */ + + if (tor_inet_aton(hostname, &in) == 0) { + /* then we have to resolve it */ + log_debug(LD_CONFIG, "Local hostname '%s' is DNS address. " + "Trying to resolve to IP address.", hostname); + explicit_ip = 0; + if (tor_lookup_hostname(hostname, &addr)) { /* failed to resolve */ + uint32_t interface_ip; /* host order */ + + if (explicit_hostname) { + log_fn(warn_severity, LD_CONFIG, + "Could not resolve local Address '%s'. Failing.", hostname); + return -1; + } + log_fn(notice_severity, LD_CONFIG, + "Could not resolve guessed local hostname '%s'. " + "Trying something else.", hostname); + if (get_interface_address(warn_severity, &interface_ip)) { + log_fn(warn_severity, LD_CONFIG, + "Could not get local interface IP address. Failing."); + return -1; + } + from_interface = 1; + addr = interface_ip; + log_fn(notice_severity, LD_CONFIG, "Learned IP address '%s' for " + "local interface. Using that.", fmt_addr32(addr)); + strlcpy(hostname, "<guessed from interfaces>", sizeof(hostname)); + } else { /* resolved hostname into addr */ + tor_addr_from_ipv4h(&myaddr, addr); + + if (!explicit_hostname && + tor_addr_is_internal(&myaddr, 0)) { + tor_addr_t interface_ip; + + log_fn(notice_severity, LD_CONFIG, "Guessed local hostname '%s' " + "resolves to a private IP address (%s). Trying something " + "else.", hostname, fmt_addr32(addr)); + + if (get_interface_address6(warn_severity, AF_INET, &interface_ip)<0) { + log_fn(warn_severity, LD_CONFIG, + "Could not get local interface IP address. Too bad."); + } else if (tor_addr_is_internal(&interface_ip, 0)) { + log_fn(notice_severity, LD_CONFIG, + "Interface IP address '%s' is a private address too. " + "Ignoring.", fmt_addr(&interface_ip)); + } else { + from_interface = 1; + addr = tor_addr_to_ipv4h(&interface_ip); + log_fn(notice_severity, LD_CONFIG, + "Learned IP address '%s' for local interface." + " Using that.", fmt_addr32(addr)); + strlcpy(hostname, "<guessed from interfaces>", sizeof(hostname)); + } + } + } + } else { + log_debug(LD_CONFIG, "Local hostname '%s' is already IP address, " + "skipping DNS resolution", hostname); + addr = ntohl(in.s_addr); /* set addr so that addr_string is not + * illformed */ + } + + /* + * Step three: Check whether 'addr' is an internal IP address, and error + * out if it is and we don't want that. + */ + + tor_addr_from_ipv4h(&myaddr,addr); + + addr_string = tor_dup_ip(addr); + if (addr_string && tor_addr_is_internal(&myaddr, 0)) { + /* make sure we're ok with publishing an internal IP */ + if (using_default_dir_authorities(options)) { + /* if they are using the default authorities, disallow internal IPs + * always. For IPv6 ORPorts, this check is done in + * router_get_advertised_ipv6_or_ap(). See #33681. */ + log_fn(warn_severity, LD_CONFIG, + "Address '%s' resolves to private IP address '%s'. " + "Tor servers that use the default DirAuthorities must have " + "public IP addresses.", hostname, addr_string); + tor_free(addr_string); + return -1; + } + if (!explicit_ip) { + /* even if they've set their own authorities, require an explicit IP if + * they're using an internal address. */ + log_fn(warn_severity, LD_CONFIG, "Address '%s' resolves to private " + "IP address '%s'. Please set the Address config option to be " + "the IP address you want to use.", hostname, addr_string); + tor_free(addr_string); + return -1; + } + } + + /* + * Step four: We have a winner! 'addr' is our answer for sure, and + * 'addr_string' is its string form. Fill out the various fields to + * say how we decided it. + */ + + log_debug(LD_CONFIG, "Resolved Address to '%s'.", addr_string); + + if (explicit_ip) { + method_used = "CONFIGURED"; + hostname_used = NULL; + } else if (explicit_hostname) { + method_used = "RESOLVED"; + hostname_used = hostname; + } else if (from_interface) { + method_used = "INTERFACE"; + hostname_used = NULL; + } else { + method_used = "GETHOSTNAME"; + hostname_used = hostname; + } + + *addr_out = addr; + if (method_out) + *method_out = method_used; + if (hostname_out) + *hostname_out = hostname_used ? tor_strdup(hostname_used) : NULL; + + /* + * Step five: Check if the answer has changed since last time (or if + * there was no last time), and if so call various functions to keep + * us up-to-date. + */ + + if (last_resolved_addr && last_resolved_addr != *addr_out) { + /* Leave this as a notice, regardless of the requested severity, + * at least until dynamic IP address support becomes bulletproof. */ + log_notice(LD_NET, + "Your IP address seems to have changed to %s " + "(METHOD=%s%s%s). Updating.", + addr_string, method_used, + hostname_used ? " HOSTNAME=" : "", + hostname_used ? hostname_used : ""); + ip_address_changed(0); + } + + if (last_resolved_addr != *addr_out) { + control_event_server_status(LOG_NOTICE, + "EXTERNAL_ADDRESS ADDRESS=%s METHOD=%s%s%s", + addr_string, method_used, + hostname_used ? " HOSTNAME=" : "", + hostname_used ? hostname_used : ""); + } + last_resolved_addr = *addr_out; + + /* + * And finally, clean up and return success. + */ + + tor_free(addr_string); + return 0; +} + +/** Return true iff <b>addr</b> is judged to be on the same network as us, or + * on a private network. + */ +MOCK_IMPL(int, +is_local_addr, (const tor_addr_t *addr)) +{ + if (tor_addr_is_internal(addr, 0)) + return 1; + /* Check whether ip is on the same /24 as we are. */ + if (get_options()->EnforceDistinctSubnets == 0) + return 0; + if (tor_addr_family(addr) == AF_INET) { + uint32_t ip = tor_addr_to_ipv4h(addr); + + /* It's possible that this next check will hit before the first time + * resolve_my_address actually succeeds. (For clients, it is likely that + * resolve_my_address will never be called at all). In those cases, + * last_resolved_addr will be 0, and so checking to see whether ip is on + * the same /24 as last_resolved_addr will be the same as checking whether + * it was on net 0, which is already done by tor_addr_is_internal. + */ + if ((last_resolved_addr & (uint32_t)0xffffff00ul) + == (ip & (uint32_t)0xffffff00ul)) + return 1; + } + return 0; +} |