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nss-mymachines: never resolve unmapped UIDs/GIDs

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Don't ever permit successful user or group lookups if no UID/GID mapping is
actually applied. THis way, we can be sure that nss-mymachines cannot be used
to insert invalid cache entries into nscd's cache.

https://bugzilla.redhat.com/show_bug.cgi?id=1285339
This commit is contained in:
Lennart Poettering 2016-02-10 22:58:41 +01:00
parent 648b122045
commit cf3bdcfeba
1 changed files with 18 additions and 2 deletions
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20
src/nss-mymachines/nss-mymachines.c
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@ -38,6 +38,9 @@ NSS_GETHOSTBYNAME_PROTOTYPES(mymachines);
NSS_GETPW_PROTOTYPES(mymachines);
NSS_GETGR_PROTOTYPES(mymachines);
#define HOST_UID_LIMIT ((uid_t) UINT32_C(0x10000))
#define HOST_GID_LIMIT ((gid_t) UINT32_C(0x10000))
static int count_addresses(sd_bus_message *m, int af, unsigned *ret) {
unsigned c = 0;
int r;
@ -455,6 +458,10 @@ enum nss_status _nss_mymachines_getpwnam_r(
if (r < 0)
goto fail;
/* Refuse to work if the mapped address is in the host UID range, or if there was no mapping at all. */
if (mapped < HOST_UID_LIMIT || mapped == uid)
goto not_found;
l = strlen(name);
if (buflen < l+1) {
*errnop = ENOMEM;
@ -504,7 +511,7 @@ enum nss_status _nss_mymachines_getpwuid_r(
}
/* We consider all uids < 65536 host uids */
if (uid < 0x10000)
if (uid < HOST_UID_LIMIT)
goto not_found;
r = sd_bus_open_system(&bus);
@ -531,6 +538,9 @@ enum nss_status _nss_mymachines_getpwuid_r(
if (r < 0)
goto fail;
if (mapped == uid)
goto not_found;
if (snprintf(buffer, buflen, "vu-%s-" UID_FMT, machine, (uid_t) mapped) >= (int) buflen) {
*errnop = ENOMEM;
return NSS_STATUS_TRYAGAIN;
@ -619,6 +629,9 @@ enum nss_status _nss_mymachines_getgrnam_r(
if (r < 0)
goto fail;
if (mapped < HOST_GID_LIMIT || mapped == gid)
goto not_found;
l = sizeof(char*) + strlen(name) + 1;
if (buflen < l) {
*errnop = ENOMEM;
@ -666,7 +679,7 @@ enum nss_status _nss_mymachines_getgrgid_r(
}
/* We consider all gids < 65536 host gids */
if (gid < 0x10000)
if (gid < HOST_GID_LIMIT)
goto not_found;
r = sd_bus_open_system(&bus);
@ -693,6 +706,9 @@ enum nss_status _nss_mymachines_getgrgid_r(
if (r < 0)
goto fail;
if (mapped == gid)
goto not_found;
if (buflen < sizeof(char*) + 1) {
*errnop = ENOMEM;
return NSS_STATUS_TRYAGAIN;