bugfix: resty.core.regex: data corruptions might happen when recursively calling ngx.re.gsub via the user replacement function argument because of incorrect reusing a globally shared captures Lua table. thanks James Hurst for the report in openresty/lua-nginx-module#445.

Author: agentzh

lib/resty/core/regex.lua

@@ -72,7 +72,6 @@ local regex_sub_str_cache = new_tab(0, 4)
 local max_regex_cache_size
 local regex_cache_size = 0
 local script_engine
-local tmp_captures = new_tab(4, 4)
 
 
 ffi.cdef[[
@@ -636,7 +635,7 @@ local function re_sub_func_helper(subj, regex, replace, opts, global)
         count = count + 1
         local prefix_len = compiled.captures[0] - cp_pos
 
-        local res = collect_captures(compiled, rc, subj, flags, tmp_captures)
+        local res = collect_captures(compiled, rc, subj, flags)
 
         local bit = replace(res)
         local bit_len = #bit

t/re-sub.t

@@ -9,7 +9,7 @@ use Cwd qw(cwd);
 
 repeat_each(2);
 
-plan tests => repeat_each() * (blocks() * 4 + 8);
+plan tests => repeat_each() * (blocks() * 4 + 9);
 
 my $pwd = cwd();
 
@@ -277,3 +277,50 @@ GET /t
 bad argument type
 NYI
 
+
+
+=== TEST 8: ngx.re.gsub: recursive calling (github openresty/lua-nginx-module#445)
+--- http_config eval: $::HttpConfig
+--- config
+
+location = /t {
+    content_by_lua '
+        function test()
+            local data = [[
+                OUTER {FIRST}
+]]
+
+            local p1 = "(OUTER)(.+)"
+            local p2 = "{([A-Z]+)}"
+
+            ngx.print(data)
+
+            local res =  ngx.re.gsub(data, p1, function(m)
+                -- ngx.say("pre: m[1]: [", m[1], "]")
+                -- ngx.say("pre: m[2]: [", m[2], "]")
+
+                local res = ngx.re.gsub(m[2], p2, function(_)
+                    return "REPLACED"
+                end, "")
+
+                -- ngx.say("post: m[1]: [", m[1], "]")
+                -- ngx.say("post m[2]: [", m[2], "]")
+                return m[1] .. res
+            end, "")
+
+            ngx.print(res)
+        end
+
+        test()
+    ';
+}
+--- request
+GET /t
+--- response_body
+                OUTER {FIRST}
+                OUTER REPLACED
+--- no_error_log
+[error]
+bad argument type
+NYI
+