implement base32 decoder

docker/nginx/Dockerfile

@@ -7,6 +7,7 @@ RUN luarocks install lua-resty-http && \
     -out /etc/ssl/local-certificate.crt
 
 COPY mo ./
+COPY libs /etc/nginx/libs
 COPY conf.d /etc/nginx/conf.d
 COPY conf.d.templates /etc/nginx/conf.d.templates
 

docker/nginx/conf.d/include/init-optional-variables

@@ -7,3 +7,6 @@ set $hns_domain '';
 
 # set only if server has been access through SERVER_DOMAIN
 set $server_alias '';
+
+# expose skylink variable so we can use it in access log
+set $skylink '';

docker/nginx/conf.d/include/location-skylink

@@ -11,6 +11,10 @@ if ($request_method = PURGE) {
 
 limit_conn downloads_by_ip 100; # ddos protection: max 100 downloads at a time
 
+# ensure that skylink that we pass around is base64 encoded (transform base32 encoded ones)
+# this is important because we want only one format in cache keys and logs
+set_by_lua_block $skylink { return require("skynet.skylink").parse(ngx.var.skylink) }
+
 # $skylink_v1 and $skylink_v2 variables default to the same value but in case the requested skylink was:
 # a) skylink v1 - it would not matter, no additional logic is executed
 # b) skylink v2 - in a lua block below we will resolve the skylink v2 into skylink v1 and update 

docker/nginx/conf.d/server/server.api

@@ -231,9 +231,6 @@ location /skynet/metadata {
     header_filter_by_lua_block {
         ngx.header["Skynet-Portal-Api"] = os.getenv("SKYNET_PORTAL_API")
         ngx.header["Skynet-Server-Api"] = os.getenv("SKYNET_SERVER_API")
-
-        -- do not expose internal header
-        ngx.header["Skynet-Requested-Skylink"] = ""
     }    
 
     proxy_set_header User-Agent: Sia-Agent;
@@ -246,9 +243,6 @@ location /skynet/resolve {
     header_filter_by_lua_block {
         ngx.header["Skynet-Portal-Api"] = os.getenv("SKYNET_PORTAL_API")
         ngx.header["Skynet-Server-Api"] = os.getenv("SKYNET_SERVER_API")
-
-        -- do not expose internal header
-        ngx.header["Skynet-Requested-Skylink"] = ""
     }    
 
     proxy_set_header User-Agent: Sia-Agent;

docker/nginx/conf.d/server/server.dnslink

@@ -37,6 +37,7 @@ location / {
             ngx.var.skylink = cache_value
         end
 
+        ngx.var.skylink = require("skynet.skylink").parse(ngx.var.skylink)
         ngx.var.skylink_v1 = ngx.var.skylink
         ngx.var.skylink_v2 = ngx.var.skylink
     }

docker/nginx/libs/skynet/skylink.lua

@@ -0,0 +1,61 @@
+local _M = {}
+
+local function str_split(str, size)
+    local result = {}
+    for i=1, #str, size do
+        table.insert(result, str:sub(i, i + size - 1))
+    end
+    return result
+end
+
+local function dec2bin(num)
+    local result = ""
+    repeat
+        local halved = num / 2
+        local int, frac = math.modf(halved)
+        num = int
+        result = math.ceil(frac) .. result
+    until num == 0
+    return result
+end
+
+local base32Alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUV"
+
+-- this is not a full implementation of base32 decoder, it doesn't 
+-- cover all edge cases but it works good enough for decoding skylinks
+-- source: https://gist.github.com/linsonder6/3202fc06832f97905aab2a8a492a80de
+function decodeBase32Skylink(str)
+    local binary = string.upper(str):gsub(".", function (char)
+        if char == "=" then return "" end
+        local pos = string.find(base32Alphabet, char)
+        pos = pos - 1
+        return string.format("%05u", dec2bin(pos))
+    end)
+
+    local bytes = str_split(binary, 8)
+
+    local decoded = {}
+    for _, byte in pairs(bytes) do
+        table.insert(decoded, string.char(tonumber(byte, 2)))
+    end
+
+    local concatenated = table.concat(decoded)
+
+    -- decoded skylink is always 34 bytes, anything
+    -- else is leftover and should be discarded
+    return string.sub(concatenated, 1, 34)
+end
+
+-- parse any skylink and return base64 version
+function _M.parse(skylink)
+    if string.len(skylink) == 55 then
+        local base64 = require("ngx.base64")
+        local decoded = decodeBase32Skylink(skylink)
+
+        return base64.encode_base64url(decoded)
+    end
+
+    return skylink
+end
+
+return _M

docker/nginx/nginx.conf

@@ -38,6 +38,8 @@ http {
     include       mime.types;
     default_type  application/octet-stream;
 
+    lua_package_path "/etc/nginx/libs/?.lua;;";
+
     log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
         '$status $body_bytes_sent "$http_referer" '
         '"$http_user_agent" $upstream_response_time '
@@ -45,7 +47,7 @@ http {
         '"$upstream_http_content_type" "$upstream_cache_status" '
         '"$server_alias" "$sent_http_skynet_skylink" '
         '$upstream_connect_time $upstream_header_time '
-        '$request_time "$hns_domain"';
+        '$request_time "$hns_domain" "$skylink"';
 
     access_log  logs/access.log  main;
 
@@ -73,7 +75,9 @@ http {
     # this runs before forking out nginx worker processes
     init_by_lua_block { 
         require "cjson"
+        require "ngx.base64"
         require "resty.http"
+        require "skynet.skylink"
     }
 
     # include skynet-portal-api and skynet-server-api header on every request