fix(core): header regex for compat mode

2 condtions:
1. only 1 header value presents
2. it starts with "~*"

Fixup #12365
Fix KAG-4788

Co-authored-by: Qi <[email protected]>

kong/db/schema/entities/routes.lua

@@ -196,10 +196,7 @@ local routes = {
             },
           },
         },
-        values = {
-          type = "array",
-          elements = typedefs.regex_or_plain_pattern,
-        }
+        values = typedefs.header_regex_or_plain_pattern,
       } },
 
       { regex_priority = { description = "A number used to choose which route resolves a given request when several routes match it using regexes simultaneously.", type = "integer", default = 0 }, },

kong/db/schema/typedefs.lua

@@ -504,14 +504,13 @@ end
 
 
 local function is_valid_regex_pattern(pattern)
-  local regex = pattern:sub(2) -- remove the leading "~"
   -- the value will be interpreted as a regex by the router; but is it a
   -- valid one? Let's dry-run it with the same options as our router.
-  local _, _, err = ngx.re.find("", regex, "aj")
+  local _, _, err = ngx.re.find("", pattern, "a")
   if err then
     return nil,
            string.format("invalid regex: '%s' (PCRE returned: %s)",
-                         regex, err)
+                         pattern, err)
   end
 
   return true
@@ -525,8 +524,9 @@ local function validate_path_with_regexes(path)
     return ok, err, err_code
   end
 
+  -- starts with `~`
   if is_regex_pattern(path) then
-    return is_valid_regex_pattern(path)
+    return is_valid_regex_pattern(path:sub(2))
   end
 
   -- prefix matching. let's check if it's normalized form
@@ -539,12 +539,14 @@ local function validate_path_with_regexes(path)
 end
 
 
-local function validate_regex_or_plain_pattern(pattern)
-  if not is_regex_pattern(pattern) then
+local function validate_header_regex_or_plain_pattern(patterns)
+  -- when there's only 1 pattern and it starts with "~*", it's a regex pattern
+  if #patterns ~= 1 or patterns[1]:sub(1, 2) ~= "~*" then
     return true
   end
 
-  return is_valid_regex_pattern(pattern)
+  -- starts with "~*"
+  return is_valid_regex_pattern(patterns[1]:sub(3))
 end
 
 
@@ -646,9 +648,12 @@ typedefs.headers = Schema.define {
   description = "A map of header names to arrays of header values."
 }
 
-typedefs.regex_or_plain_pattern = Schema.define {
-  type = "string",
-  custom_validator = validate_regex_or_plain_pattern,
+typedefs.header_regex_or_plain_pattern = Schema.define {
+  type = "array",
+  elements = {
+    type = "string",
+  },
+  custom_validator = validate_header_regex_or_plain_pattern,
   description = "A string representing a regex or plain pattern."
 }
 

kong/router/transform.lua

@@ -112,7 +112,6 @@ local OP_IN       = "in"
 
 
 local DOT              = byte(".")
-local TILDE            = byte("~")
 local ASTERISK         = byte("*")
 
 
@@ -424,12 +423,13 @@ local function get_expression(route)
     for h, v in pairs(headers) do
       single_header_buf:reset():put("(")
 
+      local num_v = #v
       for i, value in ipairs(v) do
         local name = "any(lower(http.headers." .. replace_dashes_lower(h) .. "))"
         local op = OP_EQUAL
 
-        -- value starts with "~*"
-        if byte(value, 1) == TILDE and byte(value, 2) == ASTERISK then
+        -- the condition: only 1 value and it starts with `~*`
+        if num_v == 1 and is_regex_magic(value) then
           value = value:sub(3)
           op = OP_REGEX
         end

kong/router/utils.lua

@@ -262,8 +262,9 @@ do
   local get_phase = ngx.get_phase
 
   local TILDE = byte("~")
+  local ASTERISK = byte("*")
   is_regex_magic = function(path)
-    return byte(path) == TILDE
+    return byte(path) == TILDE and byte(path, 2) == ASTERISK
   end
 
   local empty_table = {}

spec/01-unit/01-db/01-schema/06-routes_spec.lua

@@ -622,16 +622,29 @@ describe("routes schema (flavor = " .. flavor .. ")", function()
       assert.equal("length must be at least 1", err.headers[1])
     end)
 
-    it("value must be a plain pattern or a valid regex pattern", function()
-      local route = {
-        headers = { location = { "~[" } },
-        protocols = { "http" },
-      }
+    if flavor == "traditional_compatible" then
+      it("value must be a plain pattern or a valid regex pattern", function()
+        local route = {
+          headers = { location = { "~*[" } },
+          protocols = { "http" },
+        }
 
-      local ok, err = Routes:validate(route)
-      assert.falsy(ok)
-      assert.match("invalid regex", err.headers[1])
-    end)
+        local ok, err = Routes:validate(route)
+        assert.falsy(ok)
+        assert.match("invalid regex", err.headers)
+      end)
+
+      it("multiple patterns are treated as plain patterns", function()
+        local route = {
+          headers = { location = { "~*[", "~*" } },
+          protocols = { "http" },
+        }
+
+        local ok, err = Routes:validate(route)
+        assert.is_nil(err)
+        assert.truthy(ok)
+      end)
+    end
   end)
 
   describe("methods attribute", function()