Fix overflow in search_tree_size

Changes.md

@@ -1,3 +1,9 @@
+## 1.8.1
+
+* On very large databases, the calculation to determine the search tree
+  size could overflow. This was fixed and several additional guards
+  against overflows were added. Reported by Sami Salonen. GitHub #335.
+
 ## 1.8.0 - 2023-11-07
 
 * `PACKAGE_VERSION` is now a private compile definition when building

src/data-pool.c

@@ -9,8 +9,6 @@
 #include <stddef.h>
 #include <stdlib.h>
 
-static bool can_multiply(size_t const, size_t const, size_t const);
-
 // Allocate an MMDB_data_pool_s. It initially has space for size
 // MMDB_entry_data_list_s structs.
 MMDB_data_pool_s *data_pool_new(size_t const size) {
@@ -43,7 +41,7 @@ MMDB_data_pool_s *data_pool_new(size_t const size) {
 // the given max. max will typically be SIZE_MAX.
 //
 // We want to know if we'll wrap around.
-static bool can_multiply(size_t const max, size_t const m, size_t const n) {
+bool can_multiply(size_t const max, size_t const m, size_t const n) {
     if (m == 0) {
         return false;
     }

src/data-pool.h

@@ -44,6 +44,7 @@ typedef struct MMDB_data_pool_s {
     MMDB_entry_data_list_s *blocks[DATA_POOL_NUM_BLOCKS];
 } MMDB_data_pool_s;
 
+bool can_multiply(size_t const, size_t const, size_t const);
 MMDB_data_pool_s *data_pool_new(size_t const);
 void data_pool_destroy(MMDB_data_pool_s *const);
 MMDB_entry_data_list_s *data_pool_alloc(MMDB_data_pool_s *const);

src/maxminddb.c

@@ -23,6 +23,7 @@
 #endif
 #include <windows.h>
 #include <ws2ipdef.h>
+#define SSIZE_MAX INTPTR_MAX
 typedef ADDRESS_FAMILY sa_family_t;
 #else
 #include <arpa/inet.h>
@@ -289,18 +290,29 @@ int MMDB_open(const char *const filename, uint32_t flags, MMDB_s *const mmdb) {
         goto cleanup;
     }
 
-    uint32_t search_tree_size =
-        mmdb->metadata.node_count * mmdb->full_record_byte_size;
+    if (!can_multiply(SSIZE_MAX,
+                      mmdb->metadata.node_count,
+                      mmdb->full_record_byte_size)) {
+        status = MMDB_INVALID_METADATA_ERROR;
+        goto cleanup;
+    }
+    ssize_t search_tree_size = (ssize_t)mmdb->metadata.node_count *
+                               (ssize_t)mmdb->full_record_byte_size;
 
     mmdb->data_section =
         mmdb->file_content + search_tree_size + MMDB_DATA_SECTION_SEPARATOR;
-    if (search_tree_size + MMDB_DATA_SECTION_SEPARATOR >
-        (uint32_t)mmdb->file_size) {
+    if (mmdb->file_size < MMDB_DATA_SECTION_SEPARATOR ||
+        search_tree_size > mmdb->file_size - MMDB_DATA_SECTION_SEPARATOR) {
+        status = MMDB_INVALID_METADATA_ERROR;
+        goto cleanup;
+    }
+    ssize_t data_section_size =
+        mmdb->file_size - search_tree_size - MMDB_DATA_SECTION_SEPARATOR;
+    if (data_section_size > UINT32_MAX || data_section_size <= 0) {
         status = MMDB_INVALID_METADATA_ERROR;
         goto cleanup;
     }
-    mmdb->data_section_size = (uint32_t)mmdb->file_size - search_tree_size -
-                              MMDB_DATA_SECTION_SEPARATOR;
+    mmdb->data_section_size = (uint32_t)data_section_size;
 
     // Although it is likely not possible to construct a database with valid
     // valid metadata, as parsed above, and a data_section_size less than 3,