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-rw-r--r--src/nss-myhostname/nss-myhostname.c522
-rw-r--r--src/nss-myhostname/nss-myhostname.sym19
2 files changed, 541 insertions, 0 deletions
diff --git a/src/nss-myhostname/nss-myhostname.c b/src/nss-myhostname/nss-myhostname.c
new file mode 100644
index 0000000..d574e98
--- /dev/null
+++ b/src/nss-myhostname/nss-myhostname.c
@@ -0,0 +1,522 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <net/if.h>
+#include <netdb.h>
+#include <nss.h>
+#include <stdlib.h>
+
+#include "alloc-util.h"
+#include "errno-util.h"
+#include "hostname-util.h"
+#include "local-addresses.h"
+#include "macro.h"
+#include "nss-util.h"
+#include "signal-util.h"
+#include "socket-util.h"
+#include "string-util.h"
+
+/* We use 127.0.0.2 as IPv4 address. This has the advantage over
+ * 127.0.0.1 that it can be translated back to the local hostname. For
+ * IPv6 we use ::1 which unfortunately will not translate back to the
+ * hostname but instead something like "localhost" or so. */
+
+#define LOCALADDRESS_IPV4 (htobe32(0x7F000002))
+#define LOCALADDRESS_IPV6 &in6addr_loopback
+
+NSS_GETHOSTBYNAME_PROTOTYPES(myhostname);
+NSS_GETHOSTBYADDR_PROTOTYPES(myhostname);
+
+enum nss_status _nss_myhostname_gethostbyname4_r(
+ const char *name,
+ struct gaih_addrtuple **pat,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp) {
+
+ struct gaih_addrtuple *r_tuple, *r_tuple_prev = NULL;
+ _cleanup_free_ struct local_address *addresses = NULL;
+ _cleanup_free_ char *hn = NULL;
+ const char *canonical = NULL;
+ int n_addresses = 0;
+ uint32_t local_address_ipv4;
+ size_t l, idx, ms;
+ char *r_name;
+
+ PROTECT_ERRNO;
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
+
+ assert(name);
+ assert(pat);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (is_localhost(name)) {
+ /* We respond to 'localhost', so that /etc/hosts is optional */
+
+ canonical = "localhost";
+ local_address_ipv4 = htobe32(INADDR_LOOPBACK);
+
+ } else if (is_gateway_hostname(name)) {
+
+ n_addresses = local_gateways(NULL, 0, AF_UNSPEC, &addresses);
+ if (n_addresses <= 0)
+ goto not_found;
+
+ canonical = "_gateway";
+
+ } else if (is_outbound_hostname(name)) {
+
+ n_addresses = local_outbounds(NULL, 0, AF_UNSPEC, &addresses);
+ if (n_addresses <= 0)
+ goto not_found;
+
+ canonical = "_outbound";
+
+ } else {
+ hn = gethostname_malloc();
+ if (!hn) {
+ UNPROTECT_ERRNO;
+ *errnop = ENOMEM;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* We respond to our local hostname, our hostname suffixed with a single dot. */
+ if (!streq(name, hn) && !streq_ptr(startswith(name, hn), "."))
+ goto not_found;
+
+ n_addresses = local_addresses(NULL, 0, AF_UNSPEC, &addresses);
+ if (n_addresses < 0)
+ n_addresses = 0;
+
+ canonical = hn;
+ local_address_ipv4 = LOCALADDRESS_IPV4;
+ }
+
+ l = strlen(canonical);
+ ms = ALIGN(l+1) + ALIGN(sizeof(struct gaih_addrtuple)) * (n_addresses > 0 ? n_addresses : 1 + socket_ipv6_is_enabled());
+ if (buflen < ms) {
+ UNPROTECT_ERRNO;
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, fill in hostname */
+ r_name = buffer;
+ memcpy(r_name, canonical, l+1);
+ idx = ALIGN(l+1);
+
+ assert(n_addresses >= 0);
+ if (n_addresses == 0) {
+ /* Second, fill in IPv6 tuple */
+ if (socket_ipv6_is_enabled()) {
+ r_tuple = (struct gaih_addrtuple*) (buffer + idx);
+ r_tuple->next = r_tuple_prev;
+ r_tuple->name = r_name;
+ r_tuple->family = AF_INET6;
+ memcpy(r_tuple->addr, LOCALADDRESS_IPV6, 16);
+ r_tuple->scopeid = 0;
+
+ idx += ALIGN(sizeof(struct gaih_addrtuple));
+ r_tuple_prev = r_tuple;
+ }
+
+ /* Third, fill in IPv4 tuple */
+ r_tuple = (struct gaih_addrtuple*) (buffer + idx);
+ r_tuple->next = r_tuple_prev;
+ r_tuple->name = r_name;
+ r_tuple->family = AF_INET;
+ *(uint32_t*) r_tuple->addr = local_address_ipv4;
+ r_tuple->scopeid = 0;
+
+ idx += ALIGN(sizeof(struct gaih_addrtuple));
+ r_tuple_prev = r_tuple;
+ }
+
+ /* Fourth, fill actual addresses in, but in backwards order */
+ for (int i = n_addresses; i > 0; i--) {
+ struct local_address *a = addresses + i - 1;
+
+ r_tuple = (struct gaih_addrtuple*) (buffer + idx);
+ r_tuple->next = r_tuple_prev;
+ r_tuple->name = r_name;
+ r_tuple->family = a->family;
+ r_tuple->scopeid = a->family == AF_INET6 && in6_addr_is_link_local(&a->address.in6) ? a->ifindex : 0;
+ memcpy(r_tuple->addr, &a->address, 16);
+
+ idx += ALIGN(sizeof(struct gaih_addrtuple));
+ r_tuple_prev = r_tuple;
+ }
+
+ /* Verify the size matches */
+ assert(idx == ms);
+
+ /* Nscd expects us to store the first record in **pat. */
+ if (*pat)
+ **pat = *r_tuple_prev;
+ else
+ *pat = r_tuple_prev;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ /* Explicitly reset both *h_errnop and h_errno to work around
+ * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+
+not_found:
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+}
+
+static enum nss_status fill_in_hostent(
+ const char *canonical, const char *additional,
+ int af,
+ struct local_address *addresses, unsigned n_addresses,
+ uint32_t local_address_ipv4,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp,
+ char **canonp) {
+
+ size_t l_canonical, l_additional, idx, ms, alen;
+ char *r_addr, *r_name, *r_aliases, *r_alias = NULL, *r_addr_list;
+ struct local_address *a;
+ unsigned n, c;
+
+ assert(canonical);
+ assert(IN_SET(af, AF_INET, AF_INET6));
+ assert(result);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ PROTECT_ERRNO;
+
+ alen = FAMILY_ADDRESS_SIZE(af);
+
+ for (a = addresses, n = 0, c = 0; n < n_addresses; a++, n++)
+ if (af == a->family)
+ c++;
+
+ l_canonical = strlen(canonical);
+ l_additional = strlen_ptr(additional);
+ ms = ALIGN(l_canonical+1)+
+ (additional ? ALIGN(l_additional+1) : 0) +
+ sizeof(char*) +
+ (additional ? sizeof(char*) : 0) +
+ (c > 0 ? c : af == AF_INET ? 1 : socket_ipv6_is_enabled()) * ALIGN(alen) +
+ (c > 0 ? c+1 : af == AF_INET ? 2 : (unsigned) socket_ipv6_is_enabled() + 1) * sizeof(char*);
+
+ if (buflen < ms) {
+ UNPROTECT_ERRNO;
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, fill in hostnames */
+ r_name = buffer;
+ memcpy(r_name, canonical, l_canonical+1);
+ idx = ALIGN(l_canonical+1);
+
+ if (additional) {
+ r_alias = buffer + idx;
+ memcpy(r_alias, additional, l_additional+1);
+ idx += ALIGN(l_additional+1);
+ }
+
+ /* Second, create aliases array */
+ r_aliases = buffer + idx;
+ if (additional) {
+ ((char**) r_aliases)[0] = r_alias;
+ ((char**) r_aliases)[1] = NULL;
+ idx += 2*sizeof(char*);
+ } else {
+ ((char**) r_aliases)[0] = NULL;
+ idx += sizeof(char*);
+ }
+
+ /* Third, add addresses */
+ r_addr = buffer + idx;
+ if (c > 0) {
+ unsigned i = 0;
+
+ for (a = addresses, n = 0; n < n_addresses; a++, n++) {
+ if (af != a->family)
+ continue;
+
+ memcpy(r_addr + i*ALIGN(alen), &a->address, alen);
+ i++;
+ }
+
+ assert(i == c);
+ idx += c*ALIGN(alen);
+
+ } else if (af == AF_INET) {
+ *(uint32_t*) r_addr = local_address_ipv4;
+ idx += ALIGN(alen);
+ } else if (socket_ipv6_is_enabled()) {
+ memcpy(r_addr, LOCALADDRESS_IPV6, 16);
+ idx += ALIGN(alen);
+ }
+
+ /* Fourth, add address pointer array */
+ r_addr_list = buffer + idx;
+ if (c > 0) {
+ unsigned i;
+
+ for (i = 0; i < c; i++)
+ ((char**) r_addr_list)[i] = r_addr + i*ALIGN(alen);
+
+ ((char**) r_addr_list)[i] = NULL;
+ idx += (c+1) * sizeof(char*);
+
+ } else if (af == AF_INET || socket_ipv6_is_enabled()) {
+ ((char**) r_addr_list)[0] = r_addr;
+ ((char**) r_addr_list)[1] = NULL;
+ idx += 2 * sizeof(char*);
+ } else {
+ ((char**) r_addr_list)[0] = NULL;
+ idx += sizeof(char*);
+ }
+
+ /* Verify the size matches */
+ assert(idx == ms);
+
+ result->h_name = r_name;
+ result->h_aliases = (char**) r_aliases;
+ result->h_addrtype = af;
+ result->h_length = alen;
+ result->h_addr_list = (char**) r_addr_list;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ if (canonp)
+ *canonp = r_name;
+
+ /* Explicitly reset both *h_errnop and h_errno to work around
+ * https://bugzilla.redhat.com/show_bug.cgi?id=1125975 */
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+}
+
+enum nss_status _nss_myhostname_gethostbyname3_r(
+ const char *name,
+ int af,
+ struct hostent *host,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp,
+ char **canonp) {
+
+ _cleanup_free_ struct local_address *addresses = NULL;
+ const char *canonical, *additional = NULL;
+ _cleanup_free_ char *hn = NULL;
+ uint32_t local_address_ipv4 = 0;
+ int n_addresses = 0;
+
+ PROTECT_ERRNO;
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
+
+ assert(name);
+ assert(host);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (af == AF_UNSPEC)
+ af = AF_INET;
+
+ if (!IN_SET(af, AF_INET, AF_INET6)) {
+ UNPROTECT_ERRNO;
+ *errnop = EAFNOSUPPORT;
+ *h_errnop = NO_DATA;
+ return NSS_STATUS_UNAVAIL;
+ }
+
+ if (af == AF_INET6 && !socket_ipv6_is_enabled())
+ goto not_found;
+
+ if (is_localhost(name)) {
+
+ canonical = "localhost";
+ local_address_ipv4 = htobe32(INADDR_LOOPBACK);
+
+ } else if (is_gateway_hostname(name)) {
+
+ n_addresses = local_gateways(NULL, 0, af, &addresses);
+ if (n_addresses <= 0)
+ goto not_found;
+
+ canonical = "_gateway";
+
+ } else if (is_outbound_hostname(name)) {
+
+ n_addresses = local_outbounds(NULL, 0, af, &addresses);
+ if (n_addresses <= 0)
+ goto not_found;
+
+ canonical = "_outbound";
+
+ } else {
+ hn = gethostname_malloc();
+ if (!hn) {
+ UNPROTECT_ERRNO;
+ *errnop = ENOMEM;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ if (!streq(name, hn) && !streq_ptr(startswith(name, hn), "."))
+ goto not_found;
+
+ n_addresses = local_addresses(NULL, 0, af, &addresses);
+ if (n_addresses < 0)
+ n_addresses = 0;
+
+ canonical = hn;
+ additional = n_addresses <= 0 && af == AF_INET6 ? "localhost" : NULL;
+ local_address_ipv4 = LOCALADDRESS_IPV4;
+ }
+
+ UNPROTECT_ERRNO;
+
+ return fill_in_hostent(
+ canonical, additional,
+ af,
+ addresses, n_addresses,
+ local_address_ipv4,
+ host,
+ buffer, buflen,
+ errnop, h_errnop,
+ ttlp,
+ canonp);
+
+not_found:
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+}
+
+enum nss_status _nss_myhostname_gethostbyaddr2_r(
+ const void* addr, socklen_t len,
+ int af,
+ struct hostent *host,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp) {
+
+ const char *canonical = NULL, *additional = NULL;
+ uint32_t local_address_ipv4 = LOCALADDRESS_IPV4;
+ _cleanup_free_ struct local_address *addresses = NULL;
+ _cleanup_free_ char *hn = NULL;
+ int n_addresses = 0;
+ struct local_address *a;
+ bool additional_from_hostname = false;
+ unsigned n;
+
+ PROTECT_ERRNO;
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
+
+ assert(addr);
+ assert(host);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (!IN_SET(af, AF_INET, AF_INET6)) {
+ UNPROTECT_ERRNO;
+ *errnop = EAFNOSUPPORT;
+ *h_errnop = NO_DATA;
+ return NSS_STATUS_UNAVAIL;
+ }
+
+ if (len != FAMILY_ADDRESS_SIZE(af)) {
+ UNPROTECT_ERRNO;
+ *errnop = EINVAL;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
+ }
+
+ if (af == AF_INET) {
+ if ((*(uint32_t*) addr) == LOCALADDRESS_IPV4)
+ goto found;
+
+ if ((*(uint32_t*) addr) == htobe32(INADDR_LOOPBACK)) {
+ canonical = "localhost";
+ local_address_ipv4 = htobe32(INADDR_LOOPBACK);
+ goto found;
+ }
+
+ } else {
+ assert(af == AF_INET6);
+
+ if (!socket_ipv6_is_enabled())
+ goto not_found;
+
+ if (memcmp(addr, LOCALADDRESS_IPV6, 16) == 0) {
+ canonical = "localhost";
+ additional_from_hostname = true;
+ goto found;
+ }
+ }
+
+ n_addresses = local_addresses(NULL, 0, af, &addresses);
+ for (a = addresses, n = 0; (int) n < n_addresses; n++, a++)
+ if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0)
+ goto found;
+
+ addresses = mfree(addresses);
+
+ n_addresses = local_gateways(NULL, 0, af, &addresses);
+ for (a = addresses, n = 0; (int) n < n_addresses; n++, a++)
+ if (memcmp(addr, &a->address, FAMILY_ADDRESS_SIZE(af)) == 0) {
+ canonical = "_gateway";
+ goto found;
+ }
+
+not_found:
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+
+found:
+ if (!canonical || additional_from_hostname) {
+ hn = gethostname_malloc();
+ if (!hn) {
+ UNPROTECT_ERRNO;
+ *errnop = ENOMEM;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ if (!canonical)
+ canonical = hn;
+ else
+ additional = hn;
+ }
+
+ UNPROTECT_ERRNO;
+ return fill_in_hostent(
+ canonical, additional,
+ af,
+ addresses, n_addresses,
+ local_address_ipv4,
+ host,
+ buffer, buflen,
+ errnop, h_errnop,
+ ttlp,
+ NULL);
+}
+
+NSS_GETHOSTBYNAME_FALLBACKS(myhostname);
+NSS_GETHOSTBYADDR_FALLBACKS(myhostname);
diff --git a/src/nss-myhostname/nss-myhostname.sym b/src/nss-myhostname/nss-myhostname.sym
new file mode 100644
index 0000000..21ab637
--- /dev/null
+++ b/src/nss-myhostname/nss-myhostname.sym
@@ -0,0 +1,19 @@
+/***
+ SPDX-License-Identifier: LGPL-2.1-or-later
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+***/
+
+{
+global:
+ _nss_myhostname_gethostbyname_r;
+ _nss_myhostname_gethostbyname2_r;
+ _nss_myhostname_gethostbyname3_r;
+ _nss_myhostname_gethostbyname4_r;
+ _nss_myhostname_gethostbyaddr_r;
+ _nss_myhostname_gethostbyaddr2_r;
+local: *;
+};
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