tdb: put example hashes into header, so we notice incorrect hash_fn.

This is Stefan Metzmacher <metze@samba.org>'s patch with minor changes:
1) Use the TDB_MAGIC constant so both hashes aren't of strings.
2) Check the hash in tdb_check (paranoia, really).
3) Additional check in the (unlikely!) case where both examples hash to 0.
4) Cosmetic changes to var names and complaint message.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(cherry picked (modified for v3-4) from commit 786b7263000dedcb97e7369402e2e9dc967e36c4)

Signed-off-by: Stefan Metzmacher <metze@samba.org>

diff --git a/lib/tdb/common/open.c b/lib/tdb/common/open.c
index 49b8e85f1264f00c57e874916972350712b8a437..9eaa701b7d6ade35c7d0dd289c8847a6f9507ee6 100644 (file)
--- a/lib/tdb/common/open.c
+++ b/lib/tdb/common/open.c
@@ -44,6 +44,25 @@ static unsigned int default_tdb_hash(TDB_DATA *key)
        return (1103515243 * value + 12345);  
 }
 
+/* We use two hashes to double-check they're using the right hash function. */
+void tdb_header_hash(struct tdb_context *tdb,
+                    uint32_t *magic1_hash, uint32_t *magic2_hash)
+{
+       TDB_DATA hash_key;
+       uint32_t tdb_magic = TDB_MAGIC;
+
+       hash_key.dptr = (unsigned char *)TDB_MAGIC_FOOD;
+       hash_key.dsize = sizeof(TDB_MAGIC_FOOD);
+       *magic1_hash = tdb->hash_fn(&hash_key);
+
+       hash_key.dptr = CONVERT(tdb_magic);
+       hash_key.dsize = sizeof(tdb_magic);
+       *magic2_hash = tdb->hash_fn(&hash_key);
+
+       /* Make sure at least one hash is non-zero! */
+       if (*magic1_hash == 0 && *magic2_hash == 0)
+               *magic1_hash = 1;
+}
 
 /* initialise a new database with a specified hash size */
 static int tdb_new_database(struct tdb_context *tdb, int hash_size)
@@ -61,6 +80,9 @@ static int tdb_new_database(struct tdb_context *tdb, int hash_size)
        /* Fill in the header */
        newdb->version = TDB_VERSION;
        newdb->hash_size = hash_size;
+
+       tdb_header_hash(tdb, &newdb->magic1_hash, &newdb->magic2_hash);
+
        if (tdb->flags & TDB_INTERNAL) {
                tdb->map_size = size;
                tdb->map_ptr = (char *)newdb;
@@ -153,6 +175,9 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
        unsigned char *vp;
        uint32_t vertest;
        unsigned v;
+       uint32_t magic1_hash;
+       uint32_t magic2_hash;
+       const char *hash_alg;
 
        if (!(tdb = (struct tdb_context *)calloc(1, sizeof *tdb))) {
                /* Can't log this */
@@ -171,7 +196,14 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
                tdb->log.log_fn = null_log_fn;
                tdb->log.log_private = NULL;
        }
-       tdb->hash_fn = hash_fn ? hash_fn : default_tdb_hash;
+
+       if (hash_fn) {
+               tdb->hash_fn = hash_fn;
+               hash_alg = "user defined";
+       } else {
+               tdb->hash_fn = default_tdb_hash;
+               hash_alg = "default";
+       }
 
        /* cache the page size */
        tdb->page_size = getpagesize();
@@ -270,6 +302,27 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
                goto fail;
        }
 
+       tdb_header_hash(tdb, &magic1_hash, &magic2_hash);
+
+       if ((tdb->header.magic1_hash == 0) && (tdb->header.magic2_hash == 0)) {
+               /* older TDB without magic hash references */
+       } else if ((tdb->header.magic1_hash != magic1_hash) ||
+                  (tdb->header.magic2_hash != magic2_hash)) {
+               TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
+                        "%s was not created with the %s hash function we are using\n"
+                        "magic1_hash[0x%08X %s 0x%08X] "
+                        "magic2_hash[0x%08X %s 0x%08X]\n",
+                        name, hash_alg,
+                        tdb->header.magic1_hash,
+                        (tdb->header.magic1_hash == magic1_hash) ? "==" : "!=",
+                        magic1_hash,
+                        tdb->header.magic2_hash,
+                        (tdb->header.magic2_hash == magic2_hash) ? "==" : "!=",
+                        magic2_hash));
+               errno = EINVAL;
+               goto fail;
+       }
+
        /* Is it already in the open list?  If so, fail. */
        if (tdb_already_open(st.st_dev, st.st_ino)) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: "

diff --git a/lib/tdb/common/tdb_private.h b/lib/tdb/common/tdb_private.h
index 562b813ff115c4002a16c771ca6ed1172322b074..92a2a302f0ddd8ad0c646dd362885c4649d9c355 100644 (file)
--- a/lib/tdb/common/tdb_private.h
+++ b/lib/tdb/common/tdb_private.h
@@ -114,7 +114,9 @@ struct tdb_header {
        tdb_off_t rwlocks; /* obsolete - kept to detect old formats */
        tdb_off_t recovery_start; /* offset of transaction recovery region */
        tdb_off_t sequence_number; /* used when TDB_SEQNUM is set */
-       tdb_off_t reserved[29];
+       uint32_t magic1_hash; /* hash of TDB_MAGIC_FOOD. */
+       uint32_t magic2_hash; /* hash of TDB_MAGIC. */
+       tdb_off_t reserved[27];
 };
 
 struct tdb_lock_type {
@@ -209,5 +211,5 @@ void tdb_io_init(struct tdb_context *tdb);
 int tdb_expand(struct tdb_context *tdb, tdb_off_t size);
 int tdb_rec_free_read(struct tdb_context *tdb, tdb_off_t off,
                      struct list_struct *rec);
-
-
+void tdb_header_hash(struct tdb_context *tdb,
+                    uint32_t *magic1_hash, uint32_t *magic2_hash);