* Have initgroups() only add nonlocal groups to nonlocal users.

* If a group called nss-local-users exists, add local users to it.
* If a group called nss-nonlocal-users exists, add nonlocal users to it.

Signed-off-by: Tim Abbott <tabbott@mit.edu>

diff --git a/nonlocal-group.c b/nonlocal-group.c
index aa2e3905c6b14f861366683673a1b066768a9817..19d3d2c28a003f86295f79134bee2db051096848 100644 (file)
--- a/nonlocal-group.c
+++ b/nonlocal-group.c
@@ -2,7 +2,8 @@
  * nonlocal-group.c
  * group database for nss_nonlocal proxy
  *
- * Copyright © 2007 Anders Kaseorg <andersk@mit.edu>
+ * Copyright © 2007 Anders Kaseorg <andersk@mit.edu> and Tim Abbott
+ * <tabbott@mit.edu>
  *
  * Permission is hereby granted, free of charge, to any person
  * obtaining a copy of this software and associated documentation
@@ -41,6 +42,8 @@
 #include "nonlocal.h"
 
 #define MAGIC_LOCAL_GR_BUFLEN (sysconf(_SC_GETGR_R_SIZE_MAX) + 7)
+#define MAGIC_NONLOCAL_GROUPNAME "nss-nonlocal-users"
+#define MAGIC_LOCAL_GROUPNAME "nss-local-users"
 
 
 static service_user *
@@ -49,7 +52,7 @@ nss_group_nonlocal_database(void)
     static service_user *nip = NULL;
     if (nip == NULL)
        __nss_database_lookup("group_nonlocal", NULL, "", &nip);
-    
+
     return nip;
 }
 
@@ -83,6 +86,47 @@ check_nonlocal_gid(const char *user, gid_t gid, int *errnop)
     return status;
 }
 
+enum nss_status
+get_local_group(const char *name, struct group *grp, char *buffer, size_t buflen, int *errnop)
+{
+    enum nss_status status = NSS_STATUS_NOTFOUND;
+    struct group gbuf;
+    struct group *gbufp = &gbuf;
+    int ret;
+    int old_errno = errno;
+    int len = MAGIC_LOCAL_GR_BUFLEN;
+    char *buf = malloc(len);
+    if (buf == NULL) {
+       *errnop = ENOMEM;
+       errno = old_errno;
+       return NSS_STATUS_TRYAGAIN;
+    }
+    errno = 0;
+    ret = getgrnam_r(name, gbufp, buf, len, &gbufp);
+    if (ret != 0) {
+       *errnop = old_errno;
+       status = NSS_STATUS_TRYAGAIN;
+    } else if (gbufp != NULL) {
+       status = NSS_STATUS_SUCCESS;
+       grp->gr_name = strncpy(buffer, gbufp->gr_name, buflen);
+       buffer = buffer + strlen(grp->gr_name);
+       buflen = buflen - strlen(grp->gr_name);
+       grp->gr_passwd = strncpy(buffer, gbufp->gr_passwd, buflen);
+       buffer = buffer + strlen(grp->gr_passwd);
+       buflen = buflen - strlen(grp->gr_passwd);
+       grp->gr_gid = gbufp->gr_gid;
+       if (buflen < sizeof(void *)) {
+           *errnop = ERANGE;
+           status = NSS_STATUS_TRYAGAIN;
+       }
+       else {
+           grp->gr_mem = memset(buffer, 0, sizeof(void *));
+       }
+    }
+    free(buf);
+    errno = old_errno;
+    return status;
+}
 
 static service_user *grent_nip = NULL;
 static void *grent_fct_start;
@@ -202,6 +246,9 @@ _nss_nonlocal_getgrnam_r(const char *name, struct group *grp,
        void *ptr;
     } fct;
 
+    if (buflen == MAGIC_LOCAL_GR_BUFLEN)
+       return NSS_STATUS_UNAVAIL;
+
     nip = nss_group_nonlocal_database();
     if (nip == NULL)
        return NSS_STATUS_UNAVAIL;
@@ -275,6 +322,49 @@ _nss_nonlocal_initgroups_dyn(const char *user, gid_t group, long int *start,
        void *ptr;
     } fct;
     int in = *start, out = *start, i;
+    gid_t local_users_gid;
+    int is_local = 0;
+
+    // Check that the user is a nonlocal user before adding any groups
+    status = check_nonlocal_user(user, errnop);
+    if (status == NSS_STATUS_NOTFOUND) {
+       is_local = 1;
+    }
+    else if (status != NSS_STATUS_SUCCESS) {
+       return status;
+    }
+
+    int buflen = sysconf(_SC_GETGR_R_SIZE_MAX);
+    char *buffer = malloc(buflen);
+    if (buffer == NULL) {
+       *errnop = ENOMEM;
+       return NSS_STATUS_TRYAGAIN;
+    }
+    struct group local_users_group;
+    status = get_local_group(MAGIC_LOCAL_GROUPNAME,
+                            &local_users_group, buffer, buflen, errnop);
+    free(buffer);
+    if (status == NSS_STATUS_NOTFOUND) {
+       syslog(LOG_WARNING, "nss_nonlocal: Group %s does not exist locally!",
+              MAGIC_LOCAL_GROUPNAME);
+       local_users_gid = 0;
+    }
+    else if (status == NSS_STATUS_SUCCESS) {
+       if (is_local == 1) {
+           // add the (local) user to the magic local users group, and finish
+           (*groupsp)[out++] = local_users_group.gr_gid;
+           syslog(LOG_DEBUG, "nss_nonlocal: Added %s to special group %s",
+                  user, MAGIC_LOCAL_GROUPNAME);
+           *start = out;
+           return NSS_STATUS_SUCCESS;
+       }
+       else {
+           local_users_gid = local_users_group.gr_gid;
+       }
+    }
+    else {
+       return status;
+    }
 
     nip = nss_group_nonlocal_database();
     if (nip == NULL)
@@ -305,7 +395,14 @@ _nss_nonlocal_initgroups_dyn(const char *user, gid_t group, long int *start,
 
        status = check_nonlocal_gid(user, (*groupsp)[in], &nonlocal_errno);
        if (status == NSS_STATUS_SUCCESS) {
-           (*groupsp)[out++] = (*groupsp)[in];
+           // Don't let users get into MAGIC_LOCAL_GROUPNAME from nonlocal reasons.
+           if ((*groupsp)[in] == local_users_gid) {
+               syslog(LOG_WARNING, "nss_nonlocal: Nonlocal user %s removed from special local users group %s",
+                      user, MAGIC_LOCAL_GROUPNAME);
+           }
+           else {
+               (*groupsp)[out++] = (*groupsp)[in];
+           }
        } else if (status != NSS_STATUS_NOTFOUND) {
            *start = out;
            *errnop = nonlocal_errno;
@@ -313,6 +410,27 @@ _nss_nonlocal_initgroups_dyn(const char *user, gid_t group, long int *start,
        }
     }
 
+    // add the (nonlocal) user to the magic nonlocal users group
+    buflen = sysconf(_SC_GETGR_R_SIZE_MAX);
+    buffer = malloc(buflen);
+    if (buffer == NULL) {
+       *errnop = ENOMEM;
+       return NSS_STATUS_TRYAGAIN;
+    }
+    struct group nonlocal_users_group;
+    status = get_local_group(MAGIC_NONLOCAL_GROUPNAME,
+                            &nonlocal_users_group, buffer, buflen, errnop);
+    if (status == NSS_STATUS_NOTFOUND) {
+       syslog(LOG_WARNING, "nss_nonlocal: (local) group %s does not exist!",
+              MAGIC_NONLOCAL_GROUPNAME);
+    }
+    else if (status == NSS_STATUS_SUCCESS) {
+       (*groupsp)[out++] = nonlocal_users_group.gr_gid;
+       syslog(LOG_DEBUG, "nss_nonlocal: Added %s to special group %s",
+              user, MAGIC_NONLOCAL_GROUPNAME);
+    }
+    free(buffer);
+
     *start = out;
     return NSS_STATUS_SUCCESS;
 }

diff --git a/nonlocal-passwd.c b/nonlocal-passwd.c
index 15173416b0a24180bd8c877369da8eee5e3de174..041257e74cc83f6252ef3c7454ca9c1640ca7a45 100644 (file)
--- a/nonlocal-passwd.c
+++ b/nonlocal-passwd.c
@@ -2,7 +2,8 @@
  * nonlocal-passwd.c
  * passwd database for nss_nonlocal proxy.
  *
- * Copyright © 2007 Anders Kaseorg <andersk@mit.edu>
+ * Copyright © 2007 Anders Kaseorg <andersk@mit.edu> and Tim Abbott
+ * <tabbott@mit.edu>
  *
  * Permission is hereby granted, free of charge, to any person
  * obtaining a copy of this software and associated documentation
@@ -85,6 +86,33 @@ check_nonlocal_uid(const char *user, uid_t uid, int *errnop)
     return status;
 }
 
+enum nss_status
+check_nonlocal_user(const char *user, int *errnop)
+{
+    enum nss_status status = NSS_STATUS_SUCCESS;
+    struct passwd pwbuf;
+    struct passwd *pwbufp = &pwbuf;
+    int ret;
+    int old_errno = errno;
+    int buflen = MAGIC_LOCAL_PW_BUFLEN;
+    char *buf = malloc(buflen);
+    if (buf == NULL) {
+       *errnop = ENOMEM;
+       errno = old_errno;
+       return NSS_STATUS_TRYAGAIN;
+    }
+    errno = 0;
+    ret = getpwnam_r(user, pwbufp, buf, buflen, &pwbufp);
+    if (ret != 0) {
+       *errnop = errno;
+       status = NSS_STATUS_TRYAGAIN;
+    } else if (pwbufp != NULL) {
+       status = NSS_STATUS_NOTFOUND;
+    }
+    free(buf);
+    errno = old_errno;
+    return status;
+}
 
 static service_user *pwent_nip = NULL;
 static void *pwent_fct_start;
@@ -205,6 +233,9 @@ _nss_nonlocal_getpwnam_r(const char *name, struct passwd *pwd,
     } fct;
     int group_errno;
 
+    if (buflen == MAGIC_LOCAL_PW_BUFLEN)
+       return NSS_STATUS_UNAVAIL;
+
     nip = nss_passwd_nonlocal_database();
     if (nip == NULL)
        return NSS_STATUS_UNAVAIL;

diff --git a/nonlocal.h b/nonlocal.h
index c583bf46ba3ec7a88537faf5eeadaf34daabfc45..09c030bcb615968130ff703c71fbdc57f3a560b7 100644 (file)
--- a/nonlocal.h
+++ b/nonlocal.h
@@ -2,4 +2,5 @@
 #define NONLOCAL_H
 enum nss_status check_nonlocal_uid(const char *user, uid_t uid, int *errnop);
 enum nss_status check_nonlocal_gid(const char *user, gid_t gid, int *errnop);
+enum nss_status check_nonlocal_user(const char *user, int *errnop);
 #endif /* NON_LOCAL_H */