nistest.c

   1 /************************************************
   2 nss_funcs.c
   3 -------------------------------------------------
   4 based on nsstest.c by a. tridgell
   5 expanded by j. trostel
   6 -------------------------------------------------
   7 get user and group info for different nss modules
   8 ************************************************/
   9 #define _GNU_SOURCE
  10 #include <stdio.h>
  11 #include <nss.h>
  12 #include <dlfcn.h>
  13 #include <pwd.h>
  14 #include <grp.h>
  15 #include <stdlib.h>
  16
  17 typedef enum nss_status NSS_STATUS;
  18 int nss_errno;
  19
  20 void *find_fn(const char *nss_name, const char *funct_name)
  21 {
  22         char *so_path, *s;
  23         void *h;
  24         void *res;
  25
  26         // create the library name
  27         asprintf(&so_path, "libnss_%s.so.2", nss_name);
  28         h = dlopen(so_path, RTLD_LAZY);
  29
  30         if (!h){
  31                 free(so_path);
  32                 exit(1);
  33         }
  34
  35         // create the function name
  36         asprintf(&s, "_nss_%s_%s", nss_name, funct_name);
  37
  38         // and find it in the library
  39         res = dlsym(h, s);
  40
  41         if (!res) {
  42                 free(so_path);
  43                 free(s);
  44                 return NULL;
  45         }
  46
  47         // free the strings from asprintf
  48         free(so_path);
  49         free(s);
  50         return res;
  51 }
  52
  53 struct passwd *nss_getpwent(const char *nss_name)
  54 {
  55         NSS_STATUS (*_nss_getpwent_r)(struct passwd *, char *,
  56                                       size_t , int *) = find_fn(nss_name, "getpwent_r");
  57         static struct passwd pwd;
  58         static char buf[1000];
  59         NSS_STATUS status;
  60
  61         status = _nss_getpwent_r(&pwd, buf, sizeof(buf), &nss_errno);
  62
  63         if (status != NSS_STATUS_SUCCESS)
  64                 return NULL;
  65
  66         return &pwd;
  67 }
  68
  69 struct passwd *nss_getpwnam(const char *nss_name, const char *name)
  70 {
  71         NSS_STATUS (*_nss_getpwnam_r)(const char *, struct passwd *, char *,
  72                                       size_t , int *) = find_fn(nss_name, "getpwnam_r");
  73         static struct passwd pwd;
  74         static char buf[1000];
  75         NSS_STATUS status;
  76
  77         status = _nss_getpwnam_r(name, &pwd, buf, sizeof(buf), &nss_errno);
  78
  79         if (status != NSS_STATUS_SUCCESS)
  80                 return NULL;
  81
  82         return &pwd;
  83 }
  84
  85 struct passwd *nss_getpwuid(const char *nss_name, uid_t uid)
  86 {
  87         NSS_STATUS (*_nss_getpwuid_r)(uid_t, struct passwd *, char *,
  88                                       size_t , int *) = find_fn(nss_name, "getpwuid_r");
  89         static struct passwd pwd;
  90         static char buf[1000];
  91         NSS_STATUS status;
  92
  93         status = _nss_getpwuid_r(uid, &pwd, buf, sizeof(buf), &nss_errno);
  94
  95         if (status != NSS_STATUS_SUCCESS)
  96                 return NULL;
  97
  98         return &pwd;
  99 }
 100
 101 NSS_STATUS nss_setpwent(const char *nss_name)
 102 {
 103         NSS_STATUS (*_nss_setpwent)(void) = find_fn(nss_name, "setpwent");
 104         return( _nss_setpwent() );
 105 }
 106
 107 NSS_STATUS nss_endpwent(const char *nss_name)
 108 {
 109         NSS_STATUS (*_nss_endpwent)(void) = find_fn(nss_name, "endpwent");
 110         return( _nss_endpwent() );
 111 }
 112
 113 struct group *nss_getgrent(const char *nss_name)
 114 {
 115         NSS_STATUS (*_nss_getgrent_r)(struct group *, char *,
 116                                       size_t , int *) = find_fn(nss_name, "getgrent_r");
 117         static struct group grp;
 118         int my_errno = 0;
 119         static char *buf = NULL;
 120         static int buflen = 1024;
 121         NSS_STATUS status;
 122
 123         if(!buf) {
 124                 if((buf = malloc(buflen)) == NULL)
 125                 return NULL;
 126         }
 127
 128 again:
 129         status = _nss_getgrent_r(&grp, buf, buflen, &my_errno);
 130         if (status == NSS_STATUS_TRYAGAIN) {
 131                 buflen *= 2;
 132                 free(buf);
 133                 if( (buf = malloc(buflen)) == NULL) {
 134                         buflen = 1024;
 135                         return NULL;
 136                 }
 137                 goto again;
 138         }
 139
 140         if (status != NSS_STATUS_SUCCESS) {
 141                 free(buf);
 142                 buf = NULL;
 143                 return NULL;
 144         }
 145
 146         return &grp;
 147 }
 148
 149 struct group *nss_getgrnam(const char *nss_name, const char *name)
 150 {
 151         NSS_STATUS (*_nss_getgrnam_r)(const char *, struct group *, char *,
 152                                       size_t , int *) = find_fn(nss_name, "getgrnam_r");
 153         static struct group grp;
 154         static char *buf = NULL;
 155         static int buflen = 1024;
 156         NSS_STATUS status;
 157
 158         if (!buf) {
 159                 if( (buf = malloc(buflen)) == NULL)
 160                         return NULL;
 161         }
 162
 163 again:
 164         status = _nss_getgrnam_r(name, &grp, buf, buflen, &nss_errno);
 165         if (status == NSS_STATUS_TRYAGAIN) {
 166                 buflen *= 2;
 167                 free(buf);
 168                 if ( (buf = malloc(buflen)) == NULL) {
 169                         buflen = 1024;
 170                         return NULL;
 171                 }
 172                 goto again;
 173         }
 174
 175         if (status != NSS_STATUS_SUCCESS) {
 176                 free(buf);
 177                 buf = NULL;
 178                 return NULL;
 179         }
 180
 181         return &grp;
 182 }
 183
 184 struct group *nss_getgrgid(const char *nss_name, gid_t gid)
 185 {
 186         NSS_STATUS (*_nss_getgrgid_r)(gid_t, struct group *, char *,
 187                                       size_t , int *) = find_fn(nss_name, "getgrgid_r");
 188         static struct group grp;
 189         static char *buf = NULL;
 190         static int buflen = 1024;
 191         NSS_STATUS status;
 192
 193         if (!buf) {
 194                 if( (buf = malloc(buflen)) == NULL)
 195                         return NULL;
 196         }
 197
 198 again:
 199         status = _nss_getgrgid_r(gid, &grp, buf, buflen, &nss_errno);
 200         if (status ==  NSS_STATUS_TRYAGAIN) {
 201                 buflen *= 2;
 202                 free(buf);
 203                 if( (buf = malloc(buflen)) == NULL) {
 204                         buflen = 1024;
 205                         return NULL;
 206                 }
 207                 goto again;
 208         }
 209
 210         if (status != NSS_STATUS_SUCCESS) {
 211                 free(buf);
 212                 buf = NULL;
 213                 return NULL;
 214         }
 215
 216         return &grp;
 217 }
 218
 219
 220 NSS_STATUS nss_setgrent(const char *nss_name)
 221 {
 222         NSS_STATUS (*_nss_setgrent)(void) = find_fn(nss_name, "setgrent");
 223         return( _nss_setgrent() );
 224 }
 225
 226 NSS_STATUS nss_endgrent(const char *nss_name)
 227 {
 228         NSS_STATUS (*_nss_endgrent)(void) = find_fn(nss_name, "endgrent");
 229         return( _nss_endgrent() );
 230 }
 231
 232 /*
 233   this trick resets the internal glibc cached copy of the NIS domain name
 234   read the glibc nis code (in particular the __ypdomain[] static array) to
 235   understand whats going on
 236  */
 237 static void nis_reset_domain(void)
 238 {
 239         void (*fn_yp_get_default_domain)(char **);
 240         void *h = dlopen("libnss_nis.so.2", RTLD_LAZY);
 241         char *domain = NULL;
 242
 243         fn_yp_get_default_domain = dlsym(h, "yp_get_default_domain");
 244
 245         if (!fn_yp_get_default_domain) return;
 246
 247         fn_yp_get_default_domain(&domain);
 248         if (domain) {
 249                 domain[0] = 0;
 250         }
 251 }
 252
 253 int main(void)
 254 {
 255         while (1) {
 256                 struct passwd *pwd;
 257                 int i;
 258
 259                 sleep(1);
 260
 261                 nis_reset_domain();
 262
 263                 nss_setpwent("nis");
 264                 i=0;
 265                 while (nss_getpwent("nis")) i++;
 266                 printf("i=%d\n", i);
 267                 nss_endpwent("nis");
 268         }
 269         return 0;
 270 }