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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>
#include <unbound.h>
#define DEFAULT_DEBUGLEVEL 0
/*
* This is the path in Debian - in other systems it will be different
* and we will need to either somehow find it dynamically or get the path
* from the user.
*/
#define CA_BUNDLE_FILE "/etc/ssl/certs/ca-certificates.crt"
/* In the long run me might rename this file to somewhere else... */
#define TRUST_ANCHOR_FILE "./root.key"
#define MALLOC_FAILURE_STRING "Couldn't allocate memory.\n"
/* examine the result structure in detail */
void examine_result(const char *query, struct ub_result *result)
{
int i;
int num;
printf("The query is for: %s\n", query);
printf("The result has:\n");
printf("qname: %s\n", result->qname);
printf("qtype: %d\n", result->qtype);
printf("qclass: %d\n", result->qclass);
if(result->canonname)
printf("canonical name: %s\n",
result->canonname);
else printf("canonical name: <none>\n");
if(result->havedata)
printf("has data\n");
else printf("has no data\n");
if(result->nxdomain)
printf("nxdomain (name does not exist)\n");
else printf("not an nxdomain (name exists)\n");
if(result->secure)
printf("validated to be secure\n");
else printf("not validated as secure\n");
if(result->bogus)
printf("a security failure! (bogus)\n");
else printf("not a security failure (not bogus)\n");
printf("DNS rcode: %d\n", result->rcode);
if(!result->havedata)
return;
num = 0;
for(i=0; result->data[i]; i++) {
printf("result data element %d has length %d\n",
i, result->len[i]);
printf("result data element %d is: %s\n",
i, inet_ntoa(*(struct in_addr*)result->data[i]));
num++;
}
printf("result has %d data element(s)\n", num);
}
enum resolution_mode {
RECURSIVE,
FULL,
RESOLV_CONF
};
struct ub_ctx *ztdns_create_ub_context(enum resolution_mode mode,
const char *resolver_addr,
int debuglevel) {
int rc;
struct ub_ctx* ctx;
const char *error_message_format;
ctx = ub_ctx_create();
if (!ctx) {
fprintf(stderr, "Couldn't create libunbound context.\n");
return NULL;
}
if (mode == RECURSIVE) {
error_message_format = "Couldn't set forward server: %s\n";
rc = ub_ctx_set_fwd(ctx, resolver_addr);
if (rc)
goto out;
/* Make DNS over TLS mandatory for recursive resolvers */
/* TODO tls not working for some reason - this has to be fixed */
/* error_message_format = "Couldn't enable DNS over TLS: %s\n"; */
/* rc = ub_ctx_set_tls(ctx, 1); */
/* if (rc) */
/* goto out; */
/* rc = ub_ctx_set_option(ctx, "tls-cert-bundle:", CA_BUNDLE_FILE); */
} else if (mode == FULL) {
/* TODO use root_hints here for better reliability */
/* For iterative queries we use DNSSEC if possible */
error_message_format = "Couldn't set trust anchors: %s\n";
rc = ub_ctx_add_ta_autr(ctx, TRUST_ANCHOR_FILE);
} else /* if (mode == RESOLV_CONF) */ {
/* NULL can be passed to use system's default resolv.conf */
error_message_format = "Couldn't use system resolv.conf: %s\n";
rc = ub_ctx_resolvconf(ctx, NULL);
}
if (rc)
goto out;
error_message_format = "Couldn't set debuglevel: %s\n";
rc = ub_ctx_debuglevel(ctx, debuglevel);
out:
if (rc) {
fprintf(stderr, error_message_format, ub_strerror(rc));
ub_ctx_delete(ctx);
return NULL;
}
return ctx;
}
void ztdns_try_resolve(struct ub_ctx *ctx, const char *name) {
struct ub_result* result;
int rc;
rc = ub_resolve(ctx, name,
1 /* TYPE A (IPv4 address) */,
1 /* CLASS IN (internet) */, &result);
if(rc)
printf("resolve error: %s\n", ub_strerror(rc));
else {
examine_result(name, result);
ub_resolve_free(result);
}
}
struct ztdns_resolver {
struct ub_ctx *ctx;
const char *name; /* arbitrary name - only used for printing to user */
const char *address; /* IP addr in dot notation stored as string */
struct ztdns_resolver *next;
};
struct ztdns_resolver *ztdns_create_recursive_resolver(const char *name,
const char *address,
int debuglevel) {
struct ztdns_resolver *resolver;
resolver = malloc(sizeof(struct ztdns_resolver));
if (!resolver) {
fprintf(stderr, MALLOC_FAILURE_STRING);
return NULL;
}
resolver->ctx = ztdns_create_ub_context(RECURSIVE, address, debuglevel);
if (!resolver->ctx)
goto out_err;
resolver->name = name;
resolver->address = address;
resolver->next = NULL;
return resolver;
out_err:
free(resolver);
return NULL;
}
void ztdns_delete_recursive_resolver(struct ztdns_resolver *resolver) {
ub_ctx_delete(resolver->ctx);
free(resolver);
}
struct ztdns_instance {
struct ub_ctx *ctx_resolv_conf, *ctx_full;
struct ztdns_resolver *recursive_resolvers;
};
/*
* Hardcoded recursive DNS servers. A temporary solution - those should
* ideally by obtained from command line or configuration file.
*/
const char *resolvers_addresses[] = {"8.8.8.8", "8.8.4.4",
"1.1.1.1", "127.0.0.1"};
const char *resolvers_names[] = {"google", "google",
"cloudflare", "localhost"};
#define RESOLVERS_COUNT 4
int main(int argc, char** argv)
{
struct ztdns_instance ztdns;
int rc = EXIT_FAILURE;
int i;
struct ztdns_resolver *tmp;
if(argc != 2) {
printf("usage: %s HOSTNAME\n", argv[0]);
goto out_err;
}
ztdns.ctx_full =
ztdns_create_ub_context(FULL, NULL, DEFAULT_DEBUGLEVEL);
if (!ztdns.ctx_full)
goto out_err;
ztdns.ctx_resolv_conf =
ztdns_create_ub_context(RESOLV_CONF, NULL, DEFAULT_DEBUGLEVEL);
if (!ztdns.ctx_resolv_conf)
goto out_err_cleanup_ctx_full;
ztdns.recursive_resolvers = NULL;
for (i = 0; i < RESOLVERS_COUNT; i++) {
tmp = ztdns_create_recursive_resolver(resolvers_names[i],
resolvers_addresses[i],
DEFAULT_DEBUGLEVEL);
if (!tmp)
goto out_err_cleanup_recursive_resolvers;
tmp->next = ztdns.recursive_resolvers;
ztdns.recursive_resolvers = tmp;
}
printf("* FULL RESOLUTION\n");
ztdns_try_resolve(ztdns.ctx_full, argv[1]);
printf("* USING RESOLVER FROM resolv.conf\n");
ztdns_try_resolve(ztdns.ctx_resolv_conf, argv[1]);
for (tmp = ztdns.recursive_resolvers; tmp; tmp = tmp->next) {
printf("* VIA %s (%s)\n", tmp->name, tmp->address);
ztdns_try_resolve(tmp->ctx, argv[1]);
}
rc = EXIT_SUCCESS;
out_err_cleanup_recursive_resolvers:
while (ztdns.recursive_resolvers) {
tmp = ztdns.recursive_resolvers->next;
ztdns_delete_recursive_resolver(ztdns.recursive_resolvers);
ztdns.recursive_resolvers = tmp;
}
ub_ctx_delete(ztdns.ctx_resolv_conf);
out_err_cleanup_ctx_full:
ub_ctx_delete(ztdns.ctx_full);
out_err:
return rc;
}
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