JWTのkey と URL でhttp requestをキャッシュ

https://stackoverflow.com/questions/50605544/caching-api-requests-with-jwt-auth/50615736

## requirement

JWTのkey と URL が一致するかどうかでhttp requestをキャッシュする

例えば、JWT：

```
payload: {
  "iss": "iss",
  "sub": "sub",
  "userGroupID": "{userGroupID}"
}
```

そして、 https://myapi.example.com/groups/{groupID}/cars

もし userGroupIDとgroupIDと一緒だったら、キャッシュする

## 解決方法

https://github.com/jiangwenyuan/nuster キャッシュサーバーnuster

**1. Download and build, you will need lua** 

    wget https://github.com/jiangwenyuan/nuster/releases/download/v1.8.8.2/nuster-1.8.8.2.tar.gz
    
    make TARGET=linux2628 USE_ZLIB=1 USE_OPENSSL=1 USE_LUA=1 LUA_LIB=/opt/lua-5.3.1/lib LUA_INC=/opt/lua-5.3.1/include


**2. create lua script, say, jwt_group_match.lua**

     
    -- base64 FROM http://lua-users.org/wiki/BaseSixtyFour
    
    local b='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
    
    function dec(data)
        data = string.gsub(data, '[^'..b..'=]', '')
        return (data:gsub('.', function(x)
            if (x == '=') then return '' end
            local r,f='',(b:find(x)-1)
            for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end
            return r;
        end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x)
            if (#x ~= 8) then return '' end
            local c=0
            for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(8-i) or 0) end
            return string.char(c)
        end))
    end
    
    -- end base64
    
    
    -- json FROM https://gist.github.com/tylerneylon/59f4bcf316be525b30ab
    json = {}
    
    
    function kind_of(obj)
      if type(obj) ~= 'table' then return type(obj) end
      local i = 1
      for _ in pairs(obj) do
        if obj[i] ~= nil then i = i + 1 else return 'table' end
      end
      if i == 1 then return 'table' else return 'array' end
    end
    
    function escape_str(s)
      local in_char  = {'\\', '"', '/', '\b', '\f', '\n', '\r', '\t'}
      local out_char = {'\\', '"', '/',  'b',  'f',  'n',  'r',  't'}
      for i, c in ipairs(in_char) do
        s = s:gsub(c, '\\' .. out_char[i])
      end
      return s
    end
    
    function skip_delim(str, pos, delim, err_if_missing)
      pos = pos + #str:match('^%s*', pos)
      if str:sub(pos, pos) ~= delim then
        if err_if_missing then
          error('Expected ' .. delim .. ' near position ' .. pos)
        end
        return pos, false
      end
      return pos + 1, true
    end
    
    function parse_str_val(str, pos, val)
      val = val or ''
      local early_end_error = 'End of input found while parsing string.'
      if pos > #str then error(early_end_error) end
      local c = str:sub(pos, pos)
      if c == '"'  then return val, pos + 1 end
      if c ~= '\\' then return parse_str_val(str, pos + 1, val .. c) end
      -- We must have a \ character.
      local esc_map = {b = '\b', f = '\f', n = '\n', r = '\r', t = '\t'}
      local nextc = str:sub(pos + 1, pos + 1)
      if not nextc then error(early_end_error) end
      return parse_str_val(str, pos + 2, val .. (esc_map[nextc] or nextc))
    end
    
    function parse_num_val(str, pos)
      local num_str = str:match('^-?%d+%.?%d*[eE]?[+-]?%d*', pos)
      local val = tonumber(num_str)
      if not val then error('Error parsing number at position ' .. pos .. '.') end
      return val, pos + #num_str
    end
    
    json.null = {}  -- This is a one-off table to represent the null value.
    
    function json.parse(str, pos, end_delim)
      pos = pos or 1
      if pos > #str then error('Reached unexpected end of input.') end
      local pos = pos + #str:match('^%s*', pos)  -- Skip whitespace.
      local first = str:sub(pos, pos)
      if first == '{' then  -- Parse an object.
        local obj, key, delim_found = {}, true, true
        pos = pos + 1
        while true do
          key, pos = json.parse(str, pos, '}')
          if key == nil then return obj, pos end
          if not delim_found then error('Comma missing between object items.') end
          pos = skip_delim(str, pos, ':', true)  -- true -> error if missing.
          obj[key], pos = json.parse(str, pos)
          pos, delim_found = skip_delim(str, pos, ',')
        end
      elseif first == '[' then  -- Parse an array.
        local arr, val, delim_found = {}, true, true
        pos = pos + 1
        while true do
          val, pos = json.parse(str, pos, ']')
          if val == nil then return arr, pos end
          if not delim_found then error('Comma missing between array items.') end
          arr[#arr + 1] = val
          pos, delim_found = skip_delim(str, pos, ',')
        end
      elseif first == '"' then  -- Parse a string.
        return parse_str_val(str, pos + 1)
      elseif first == '-' or first:match('%d') then  -- Parse a number.
        return parse_num_val(str, pos)
      elseif first == end_delim then  -- End of an object or array.
        return nil, pos + 1
      else  -- Parse true, false, or null.
        local literals = {['true'] = true, ['false'] = false, ['null'] = json.null}
        for lit_str, lit_val in pairs(literals) do
          local lit_end = pos + #lit_str - 1
          if str:sub(pos, lit_end) == lit_str then return lit_val, lit_end + 1 end
        end
        local pos_info_str = 'position ' .. pos .. ': ' .. str:sub(pos, pos + 10)
        error('Invalid json syntax starting at ' .. pos_info_str)
      end
    end
    
    -- end json
    
    
    
    
    
    
    -- nuster jwt
    
    
    function jwt_group_match(txn)
    
      local hdr = txn.http:req_get_headers()
      local jwt = hdr["jwt"]
      if jwt == nil then
        return false
      end

      _, payload, _ = jwt[0]:match"([^.]*)%.([^.]*)%.(.*)"
      if payload == nil then
        return false
      end

      local payload_dec = dec(payload)
      local payload_json = json.parse(payload_dec)


      if txn.sf:path() == "/group/" ..  payload_json["userGroupID"] .. "/cars" then
        return true
      end

      return false
    end
    
    core.register_fetches("jwt_group_match", jwt_group_match)


**3. create conf, say, nuster.conf**

    global
        nuster cache on dict-size 1m data-size 100m
        debug
        lua-load jwt_group_match.lua
    
    frontend web1
        bind *:8080
        mode http
    
        default_backend app1
    
    backend app1
        mode http
        http-request set-var(req.jwt_group_match) lua.jwt_group_match
    
        nuster cache on
        nuster rule group if { var(req.jwt_group_match) -m bool }
    
    
        server s1 127.0.0.1:8000
        server s2 127.0.0.1:8001

**3. start nuster**

    ./haproxy -f nuster.conf


**TEST**

    payload: {
      "iss": "iss",
      "sub": "sub",
      "userGroupID": "nuster"
    }

    curl http://127.0.0.1:8080/group/nuster/cars --header "jwt: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJpc3MiLCJzdWIiOiJzdWIiLCJ1c2VyR3JvdXBJRCI6Im51c3RlciJ9.hPpqQS0d4T2BQP90ZDcgxnqJ0AHmwWFqZvdxu65X3FM"


First run

    [CACHE] To create

Second run

    [CACHE] Hit