machine: make sure unpriviliged "machinectl status" can show the machine's OS version

[elogind.git] / src / nss-resolve / nss-resolve.c

diff --git a/src/nss-resolve/nss-resolve.c b/src/nss-resolve/nss-resolve.c
index c172022d76532e89214f8509350d261b1e3376b2..ccbc7317f647593a16a4640df9920c5f1f79d73b 100644 (file)
--- a/src/nss-resolve/nss-resolve.c
+++ b/src/nss-resolve/nss-resolve.c
@@ -29,6 +29,7 @@
 #include <net/if.h>
 #include <stdlib.h>
 #include <arpa/inet.h>
+#include <dlfcn.h>
 
 #include "sd-bus.h"
 #include "bus-util.h"
@@ -43,6 +44,27 @@ NSS_GETHOSTBYADDR_PROTOTYPES(resolve);
 
 #define DNS_CALL_TIMEOUT_USEC (45*USEC_PER_SEC)
 
+typedef void (*voidfunc_t)(void);
+
+static voidfunc_t find_fallback(const char *module, const char *symbol) {
+        void *dl;
+
+        /* Try to find a fallback NSS module symbol */
+
+        dl = dlopen(module, RTLD_LAZY|RTLD_NODELETE);
+        if (!dl)
+                return NULL;
+
+        return dlsym(dl, symbol);
+}
+
+static bool bus_error_shall_fallback(sd_bus_error *e) {
+        return sd_bus_error_has_name(e, SD_BUS_ERROR_SERVICE_UNKNOWN) ||
+               sd_bus_error_has_name(e, SD_BUS_ERROR_NAME_HAS_NO_OWNER) ||
+               sd_bus_error_has_name(e, SD_BUS_ERROR_NO_REPLY) ||
+               sd_bus_error_has_name(e, SD_BUS_ERROR_ACCESS_DENIED);
+}
+
 static int count_addresses(sd_bus_message *m, int af, const char **canonical) {
         int c = 0, r;
 
@@ -101,7 +123,7 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         _cleanup_bus_message_unref_ sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         struct gaih_addrtuple *r_tuple, *r_tuple_first = NULL;
-        _cleanup_bus_unref_ sd_bus *bus = NULL;
+        _cleanup_bus_close_unref_ sd_bus *bus = NULL;
         const char *canonical = NULL;
         size_t l, ms, idx;
         char *r_name;
@@ -131,7 +153,7 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         if (r < 0)
                 goto fail;
 
-        r = sd_bus_message_append(req, "sy", name, AF_UNSPEC);
+        r = sd_bus_message_append(req, "si", name, AF_UNSPEC);
         if (r < 0)
                 goto fail;
 
@@ -143,6 +165,25 @@ enum nss_status _nss_resolve_gethostbyname4_r(
                         return NSS_STATUS_NOTFOUND;
                 }
 
+                if (bus_error_shall_fallback(&error)) {
+
+                        enum nss_status (*fallback)(
+                                        const char *name,
+                                        struct gaih_addrtuple **pat,
+                                        char *buffer, size_t buflen,
+                                        int *errnop, int *h_errnop,
+                                        int32_t *ttlp);
+
+                        fallback = (enum nss_status (*)(const char *name,
+                                                        struct gaih_addrtuple **pat,
+                                                        char *buffer, size_t buflen,
+                                                        int *errnop, int *h_errnop,
+                                                        int32_t *ttlp))
+                                find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname4_r");
+                        if (fallback)
+                                return fallback(name, pat, buffer, buflen, errnop, h_errnop, ttlp);
+                }
+
                 *errnop = -r;
                 *h_errnop = NO_RECOVERY;
                 return NSS_STATUS_UNAVAIL;
@@ -240,6 +281,11 @@ enum nss_status _nss_resolve_gethostbyname4_r(
         if (ttlp)
                 *ttlp = 0;
 
+        /* Explicitly reset all error variables */
+        *errnop = 0;
+        *h_errnop = NETDB_SUCCESS;
+        h_errno = 0;
+
         return NSS_STATUS_SUCCESS;
 
 fail:
@@ -260,7 +306,7 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         _cleanup_bus_message_unref_ sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         char *r_name, *r_aliases, *r_addr, *r_addr_list;
-        _cleanup_bus_unref_ sd_bus *bus = NULL;
+        _cleanup_bus_close_unref_ sd_bus *bus = NULL;
         size_t l, idx, ms, alen;
         const char *canonical;
         int c, r, i = 0;
@@ -297,7 +343,7 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         if (r < 0)
                 goto fail;
 
-        r = sd_bus_message_append(req, "sy", name, af);
+        r = sd_bus_message_append(req, "si", name, af);
         if (r < 0)
                 goto fail;
 
@@ -309,6 +355,29 @@ enum nss_status _nss_resolve_gethostbyname3_r(
                         return NSS_STATUS_NOTFOUND;
                 }
 
+                if (bus_error_shall_fallback(&error)) {
+
+                        enum nss_status (*fallback)(
+                                        const char *name,
+                                        int af,
+                                        struct hostent *result,
+                                        char *buffer, size_t buflen,
+                                        int *errnop, int *h_errnop,
+                                        int32_t *ttlp,
+                                        char **canonp);
+
+                        fallback =  (enum nss_status (*)(const char *name,
+                                                         int af,
+                                                         struct hostent *result,
+                                                         char *buffer, size_t buflen,
+                                                         int *errnop, int *h_errnop,
+                                                         int32_t *ttlp,
+                                                         char **canonp))
+                                find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname3_r");
+                        if (fallback)
+                                return fallback(name, af, result, buffer, buflen, errnop, h_errnop, ttlp, canonp);
+                }
+
                 *errnop = -r;
                 *h_errnop = NO_RECOVERY;
                 return NSS_STATUS_UNAVAIL;
@@ -418,6 +487,11 @@ enum nss_status _nss_resolve_gethostbyname3_r(
         result->h_length = alen;
         result->h_addr_list = (char**) r_addr_list;
 
+        /* Explicitly reset all error variables */
+        *errnop = 0;
+        *h_errnop = NETDB_SUCCESS;
+        h_errno = 0;
+
         if (ttlp)
                 *ttlp = 0;
 
@@ -443,7 +517,7 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
         _cleanup_bus_message_unref_ sd_bus_message *req = NULL, *reply = NULL;
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         char *r_name, *r_aliases, *r_addr, *r_addr_list;
-        _cleanup_bus_unref_ sd_bus *bus = NULL;
+        _cleanup_bus_close_unref_ sd_bus *bus = NULL;
         unsigned c = 0, i = 0;
         size_t ms = 0, idx;
         const char *n;
@@ -505,6 +579,29 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
                         return NSS_STATUS_NOTFOUND;
                 }
 
+                if (bus_error_shall_fallback(&error)) {
+
+                        enum nss_status (*fallback)(
+                                        const void* addr, socklen_t len,
+                                        int af,
+                                        struct hostent *result,
+                                        char *buffer, size_t buflen,
+                                        int *errnop, int *h_errnop,
+                                        int32_t *ttlp);
+
+                        fallback = (enum nss_status (*)(
+                                        const void* addr, socklen_t len,
+                                        int af,
+                                        struct hostent *result,
+                                        char *buffer, size_t buflen,
+                                        int *errnop, int *h_errnop,
+                                        int32_t *ttlp))
+                                find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyaddr2_r");
+
+                        if (fallback)
+                                return fallback(addr, len, af, result, buffer, buflen, errnop, h_errnop, ttlp);
+                }
+
                 *errnop = -r;
                 *h_errnop = NO_RECOVERY;
                 return NSS_STATUS_UNAVAIL;
@@ -588,6 +685,11 @@ enum nss_status _nss_resolve_gethostbyaddr2_r(
         if (ttlp)
                 *ttlp = 0;
 
+        /* Explicitly reset all error variables */
+        *errnop = 0;
+        *h_errnop = NETDB_SUCCESS;
+        h_errno = 0;
+
         return NSS_STATUS_SUCCESS;
 
 fail: