mmap_cache: "Override" functions for initgr mmap cache

Functions sss_mc_get_strs_offset and sss_mc_get_strs_len provides
data about strings for individual memory caches (passwd, ...)
Their are used in generic responder mmap cache code to find a record
in mmap cache (sss_mc_find_record). Data provided from functions sss_mc_get_*
are used for checking the validity of record. So in case of corrupted record
the whole mmap cache can be invalidated.

Functions sss_mc_get_strs_offset and sss_mc_get_strs_len did not provide
data for initgroups mmap cache and therefore particular record could not be
invalidated.

Resolves:
https://fedorahosted.org/sssd/ticket/2716

Reviewed-by: Michal Židek <mzidek@redhat.com>

3 files changed, 28 insertions, 9 deletions

diff --git a/src/responder/nss/nsssrv_mmap_cache.c b/src/responder/nss/nsssrv_mmap_cache.c
index 16bc926f3..ab9e769b1 100644
--- a/src/responder/nss/nsssrv_mmap_cache.c
+++ b/src/responder/nss/nsssrv_mmap_cache.c
@@ -475,6 +475,9 @@ static errno_t sss_mc_get_strs_offset(struct sss_mc_ctx *mcc,
     case SSS_MC_GROUP:
         *_offset = offsetof(struct sss_mc_grp_data, strs);
         return EOK;
+    case SSS_MC_INITGROUPS:
+        *_offset = offsetof(struct sss_mc_initgr_data, gids);
+        return EOK;
     default:
         DEBUG(SSSDBG_FATAL_FAILURE, "Unknown memory cache type.\n");
         return EINVAL;
@@ -492,6 +495,9 @@ static errno_t sss_mc_get_strs_len(struct sss_mc_ctx *mcc,
     case SSS_MC_GROUP:
         *_len = ((struct sss_mc_grp_data *)&rec->data)->strs_len;
         return EOK;
+    case SSS_MC_INITGROUPS:
+        *_len = ((struct sss_mc_initgr_data *)&rec->data)->data_len;
+        return EOK;
     default:
         DEBUG(SSSDBG_FATAL_FAILURE, "Unknown memory cache type.\n");
         return EINVAL;
@@ -974,8 +980,8 @@ errno_t sss_mmap_cache_initgr_store(struct sss_mc_ctx **_mcc,
         return EINVAL;
     }
 
-    /* num_groups + reserved + array of gids + name*/
-    data_len = (2 + num_groups) * sizeof(uint32_t) + name->len;
+    /* array of gids + name */
+    data_len = num_groups * sizeof(uint32_t) + name->len;
     rec_len = sizeof(struct sss_mc_rec) + sizeof(struct sss_mc_initgr_data)
               + data_len;
     if (rec_len > mcc->dt_size) {
@@ -998,10 +1004,13 @@ errno_t sss_mmap_cache_initgr_store(struct sss_mc_ctx **_mcc,
                             name->str, name->len, name->str, name->len);
 
     /* initgroups struct */
+    data->strs_len = name->len;
+    data->data_len = data_len;
+    data->reserved = MC_INVALID_VAL32;
     data->num_groups = num_groups;
     memcpy(data->gids, gids_buf, num_groups * sizeof(uint32_t));
     memcpy(&data->gids[num_groups], name->str, name->len);
-    data->name = MC_PTR_DIFF(&data->gids[num_groups], data);
+    data->strs = data->name = MC_PTR_DIFF(&data->gids[num_groups], data);
 
     MC_LOWER_BARRIER(rec);
 
diff --git a/src/sss_client/nss_mc_initgr.c b/src/sss_client/nss_mc_initgr.c
index e21b9f40a..153617ea9 100644
--- a/src/sss_client/nss_mc_initgr.c
+++ b/src/sss_client/nss_mc_initgr.c
@@ -93,6 +93,7 @@ errno_t sss_nss_mc_initgroups_dyn(const char *name, size_t name_len,
     uint32_t hash;
     uint32_t slot;
     int ret;
+    const size_t data_offset = offsetof(struct sss_mc_initgr_data, gids);
     uint8_t *max_addr;
 
     ret = sss_nss_mc_get_ctx("initgroups", &initgr_mc_ctx);
@@ -128,16 +129,21 @@ errno_t sss_nss_mc_initgroups_dyn(const char *name, size_t name_len,
         }
 
         data = (struct sss_mc_initgr_data *)rec->data;
+        rec_name = (char *)data + data->name;
         /* Integrity check
-         * - array with gids must be within data_table
-         * - string must be within data_table */
-        if ((uint8_t *)data->gids > max_addr
-                || (uint8_t *)data + data->name + name_len > max_addr) {
+         * - name_len cannot be longer than all strings or data
+         * - data->name cannot point outside strings
+         * - all data must be within data_table
+         * - name must be within data_table */
+        if (name_len > data->data_len
+            || name_len > data->strs_len
+            || (data->strs + name_len) > (data_offset + data->data_len)
+            || (uint8_t *)data->gids + data->data_len > max_addr
+            || (uint8_t *)rec_name + name_len > max_addr) {
             ret = ENOENT;
             goto done;
         }
 
-        rec_name = (char *)data + data->name;
         if (strcmp(name, rec_name) == 0) {
             break;
         }
diff --git a/src/util/mmap_cache.h b/src/util/mmap_cache.h
index a8703d5da..b5917b3c0 100644
--- a/src/util/mmap_cache.h
+++ b/src/util/mmap_cache.h
@@ -79,7 +79,7 @@ typedef uint32_t rel_ptr_t;
 
 
 #define SSS_MC_MAJOR_VNO    1
-#define SSS_MC_MINOR_VNO    0
+#define SSS_MC_MINOR_VNO    1
 
 #define SSS_MC_HEADER_UNINIT    0   /* after ftruncate or before reset */
 #define SSS_MC_HEADER_ALIVE     1   /* current and in use */
@@ -139,6 +139,10 @@ struct sss_mc_grp_data {
 
 struct sss_mc_initgr_data {
     rel_ptr_t name;         /* ptr to name string, rel. to struct base addr */
+    rel_ptr_t strs;         /* ptr to concatenation of all strings */
+    uint32_t reserved;
+    uint32_t strs_len;      /* length of strs */
+    uint32_t data_len;      /* all initgroups data len */
     uint32_t num_groups;    /* number of groups */
     uint32_t gids[0];       /* array of all groups
                              * string with name is stored after gids */