141 lines
6.4 KiB
Diff
141 lines
6.4 KiB
Diff
From 666ed7facf4524bf6d19b11b20faa2cf93fdf591 Mon Sep 17 00:00:00 2001
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From: "meir@redislabs.com" <meir@redislabs.com>
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Date: Sun, 13 Jun 2021 14:27:18 +0300
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Subject: [PATCH] Fix invalid memory write on lua stack overflow
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{CVE-2021-32626}
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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When LUA call our C code, by default, the LUA stack has room for 20
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elements. In most cases, this is more than enough but sometimes it's not
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and the caller must verify the LUA stack size before he pushes elements.
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On 3 places in the code, there was no verification of the LUA stack size.
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On specific inputs this missing verification could have lead to invalid
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memory write:
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1. On 'luaReplyToRedisReply', one might return a nested reply that will
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explode the LUA stack.
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2. On 'redisProtocolToLuaType', the Redis reply might be deep enough
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to explode the LUA stack (notice that currently there is no such
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command in Redis that returns such a nested reply, but modules might
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do it)
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3. On 'ldbRedis', one might give a command with enough arguments to
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explode the LUA stack (all the arguments will be pushed to the LUA
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stack)
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This commit is solving all those 3 issues by calling 'lua_checkstack' and
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verify that there is enough room in the LUA stack to push elements. In
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case 'lua_checkstack' returns an error (there is not enough room in the
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LUA stack and it's not possible to increase the stack), we will do the
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following:
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1. On 'luaReplyToRedisReply', we will return an error to the user.
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2. On 'redisProtocolToLuaType' we will exit with panic (we assume this
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scenario is rare because it can only happen with a module).
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3. On 'ldbRedis', we return an error.
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---
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src/scripting.c | 41 +++++++++++++++++++++++++++++++++++++++++
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1 file changed, 41 insertions(+)
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diff --git a/src/scripting.c b/src/scripting.c
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index dea5f516561..afa6adb0c47 100644
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--- a/src/scripting.c
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+++ b/src/scripting.c
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@@ -128,6 +128,16 @@ void sha1hex(char *digest, char *script, size_t len) {
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*/
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char *redisProtocolToLuaType(lua_State *lua, char* reply) {
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+
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+ if (!lua_checkstack(lua, 5)) {
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+ /*
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+ * Increase the Lua stack if needed, to make sure there is enough room
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+ * to push 5 elements to the stack. On failure, exit with panic.
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+ * Notice that we need, in the worst case, 5 elements because redisProtocolToLuaType_Aggregate
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+ * might push 5 elements to the Lua stack.*/
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+ serverPanic("lua stack limit reach when parsing redis.call reply");
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+ }
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+
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char *p = reply;
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switch(*p) {
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@@ -220,6 +230,11 @@ char *redisProtocolToLuaType_Aggregate(lua_State *lua, char *reply, int atype) {
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if (atype == '%') {
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p = redisProtocolToLuaType(lua,p);
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} else {
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+ if (!lua_checkstack(lua, 1)) {
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+ /* Notice that here we need to check the stack again because the recursive
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+ * call to redisProtocolToLuaType might have use the room allocated in the stack */
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+ serverPanic("lua stack limit reach when parsing redis.call reply");
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+ }
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lua_pushboolean(lua,1);
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}
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lua_settable(lua,-3);
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@@ -339,6 +354,17 @@ void luaSortArray(lua_State *lua) {
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/* Reply to client 'c' converting the top element in the Lua stack to a
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* Redis reply. As a side effect the element is consumed from the stack. */
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void luaReplyToRedisReply(client *c, lua_State *lua) {
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+
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+ if (!lua_checkstack(lua, 4)) {
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+ /* Increase the Lua stack if needed to make sure there is enough room
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+ * to push 4 elements to the stack. On failure, return error.
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+ * Notice that we need, in the worst case, 4 elements because returning a map might
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+ * require push 4 elements to the Lua stack.*/
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+ addReplyErrorFormat(c, "reached lua stack limit");
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+ lua_pop(lua,1); // pop the element from the stack
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+ return;
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+ }
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+
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int t = lua_type(lua,-1);
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switch(t) {
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@@ -362,6 +388,7 @@ void luaReplyToRedisReply(client *c, lua_State *lua) {
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* field. */
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/* Handle error reply. */
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+ // we took care of the stack size on function start
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lua_pushstring(lua,"err");
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lua_gettable(lua,-2);
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t = lua_type(lua,-1);
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@@ -407,6 +434,7 @@ void luaReplyToRedisReply(client *c, lua_State *lua) {
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if (t == LUA_TTABLE) {
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int maplen = 0;
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void *replylen = addReplyDeferredLen(c);
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+ /* we took care of the stack size on function start */
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lua_pushnil(lua); /* Use nil to start iteration. */
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while (lua_next(lua,-2)) {
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/* Stack now: table, key, value */
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@@ -429,6 +457,7 @@ void luaReplyToRedisReply(client *c, lua_State *lua) {
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if (t == LUA_TTABLE) {
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int setlen = 0;
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void *replylen = addReplyDeferredLen(c);
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+ /* we took care of the stack size on function start */
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lua_pushnil(lua); /* Use nil to start iteration. */
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while (lua_next(lua,-2)) {
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/* Stack now: table, key, true */
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@@ -448,6 +477,7 @@ void luaReplyToRedisReply(client *c, lua_State *lua) {
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void *replylen = addReplyDeferredLen(c);
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int j = 1, mbulklen = 0;
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while(1) {
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+ /* we took care of the stack size on function start */
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lua_pushnumber(lua,j++);
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lua_gettable(lua,-2);
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t = lua_type(lua,-1);
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@@ -2506,6 +2536,17 @@ void ldbEval(lua_State *lua, sds *argv, int argc) {
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void ldbRedis(lua_State *lua, sds *argv, int argc) {
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int j, saved_rc = server.lua_replicate_commands;
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+ if (!lua_checkstack(lua, argc + 1)) {
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+ /* Increase the Lua stack if needed to make sure there is enough room
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+ * to push 'argc + 1' elements to the stack. On failure, return error.
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+ * Notice that we need, in worst case, 'argc + 1' elements because we push all the arguments
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+ * given by the user (without the first argument) and we also push the 'redis' global table and
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+ * 'redis.call' function so:
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+ * (1 (redis table)) + (1 (redis.call function)) + (argc - 1 (all arguments without the first)) = argc + 1*/
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+ ldbLogRedisReply("max lua stack reached");
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+ return;
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+ }
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+
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lua_getglobal(lua,"redis");
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lua_pushstring(lua,"call");
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lua_gettable(lua,-2); /* Stack: redis, redis.call */
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