auth-filters: add simple file-based authentication scheme

[ps-cgit] / filters / simple-authentication.lua

diff --git a/filters/simple-authentication.lua b/filters/simple-authentication.lua
index 4cd498313fd72276f760f1ccb23e518e256f36b5..77d1fd061f2df0ebbf19cf3153022a17fae1a794 100644 (file)
--- a/filters/simple-authentication.lua
+++ b/filters/simple-authentication.lua
@@ -3,7 +3,12 @@
 -- Requirements:
 --     luacrypto >= 0.3
 --     <http://mkottman.github.io/luacrypto/>
 -- Requirements:
 --     luacrypto >= 0.3
 --     <http://mkottman.github.io/luacrypto/>

+--     luaposix
+--     <https://github.com/luaposix/luaposix>

 --
 --

+local sysstat = require("posix.sys.stat")
+local unistd = require("posix.unistd")
+local crypto = require("crypto")

 
 
 --
 
 
 --


@@ -12,20 +17,22 @@
 --
 --
 
 --
 --
 

+-- A list of password protected repositories along with the users who can access them.

 local protected_repos = {
        glouglou        = { laurent = true, jason = true },
        qt              = { jason = true, bob = true }
 }
 
 local protected_repos = {
        glouglou        = { laurent = true, jason = true },
        qt              = { jason = true, bob = true }
 }
 

+-- A list of users and hashes, generated with `mkpasswd -m sha-512 -R 300000`.

 local users = {
 local users = {

-       jason           = "secretpassword",
-       laurent         = "s3cr3t",
-       bob             = "ilikelua"
+       jason           = "$6$rounds=300000$YYJct3n/o.ruYK$HhpSeuCuW1fJkpvMZOZzVizeLsBKcGA/aF2UPuV5v60JyH2MVSG6P511UMTj2F3H75.IT2HIlnvXzNb60FcZH1",
+       laurent         = "$6$rounds=300000$dP0KNHwYb3JKigT$pN/LG7rWxQ4HniFtx5wKyJXBJUKP7R01zTNZ0qSK/aivw8ywGAOdfYiIQFqFhZFtVGvr11/7an.nesvm8iJUi.",
+       bob             = "$6$rounds=300000$jCLCCt6LUpTz$PI1vvd1yaVYcCzqH8QAJFcJ60b6W/6sjcOsU7mAkNo7IE8FRGW1vkjF8I/T5jt/auv5ODLb1L4S2s.CAyZyUC"

 }
 
 }
 

-local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
-
-
+-- Set this to a path this script can write to for storing a persistent
+-- cookie secret, which should be guarded.
+local secret_filename = "/var/cache/cgit/auth-secret"

 
 --
 --
 
 --
 --


@@ -33,15 +40,27 @@ local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
 --
 --
 
 --
 --
 

--- Sets HTTP cookie headers based on post
+-- Sets HTTP cookie headers based on post and sets up redirection.

 function authenticate_post()
 function authenticate_post()

-       local password = users[post["username"]]
-       -- TODO: Implement time invariant string comparison function to mitigate against timing attack.
-       if password == nil or password ~= post["password"] then
-               construct_cookie("", "cgitauth")
+       local hash = users[post["username"]]
+       local redirect = validate_value("redirect", post["redirect"])
+
+       if redirect == nil then
+               not_found()
+               return 0
+       end
+
+       redirect_to(redirect)
+
+       if hash == nil or hash ~= unistd.crypt(post["password"], hash) then
+               set_cookie("cgitauth", "")

        else
        else

-               construct_cookie(post["username"], "cgitauth")
+               -- One week expiration time
+               local username = secure_value("username", post["username"], os.time() + 604800)
+               set_cookie("cgitauth", username)

        end
        end

+
+       html("\n")

        return 0
 end
 
        return 0
 end
 


@@ -54,8 +73,8 @@ function authenticate_cookie()
                return 1
        end
 
                return 1
        end
 

-       local username = validate_cookie(get_cookie(http["cookie"], "cgitauth"))
-       if username == nil or not accepted_users[username] then
+       local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))
+       if username == nil or not accepted_users[username:lower()] then

                return 0
        else
                return 1
                return 0
        else
                return 1


@@ -68,6 +87,9 @@ function body()
        html("<form method='post' action='")
        html_attr(cgit["login"])
        html("'>")
        html("<form method='post' action='")
        html_attr(cgit["login"])
        html("'>")

+       html("<input type='hidden' name='redirect' value='")
+       html_attr(secure_value("redirect", cgit["url"], 0))
+       html("' />")

        html("<table>")
        html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
        html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
        html("<table>")
        html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
        html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")


@@ -78,81 +100,10 @@ function body()
 end
 
 
 end
 
 

---
---
--- Cookie construction and validation helpers.
---
---
-
-local crypto = require("crypto")
-
--- Returns username of cookie if cookie is valid. Otherwise returns nil.
-function validate_cookie(cookie)
-       local i = 0
-       local username = ""
-       local expiration = 0
-       local salt = ""
-       local hmac = ""
-
-       if cookie:len() < 3 or cookie:sub(1, 1) == "|" then
-               return nil
-       end
-
-       for component in string.gmatch(cookie, "[^|]+") do
-               if i == 0 then
-                       username = component
-               elseif i == 1 then
-                       expiration = tonumber(component)
-                       if expiration == nil then
-                               expiration = 0
-                       end
-               elseif i == 2 then
-                       salt = component
-               elseif i == 3 then
-                       hmac = component
-               else
-                       break
-               end
-               i = i + 1
-       end
-
-       if hmac == nil or hmac:len() == 0 then
-               return nil
-       end
-
-       -- TODO: implement time invariant comparison to prevent against timing attack.
-       if hmac ~= crypto.hmac.digest("sha1", username .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
-               return nil
-       end
-
-       if expiration <= os.time() then
-               return nil
-       end
-
-       return username:lower()
-end
-
-function construct_cookie(username, cookie)
-       local authstr = ""
-       if username:len() > 0 then
-               -- One week expiration time
-               local expiration = os.time() + 604800
-               local salt = crypto.hex(crypto.rand.bytes(16))
-
-               authstr = username .. "|" .. tostring(expiration) .. "|" .. salt
-               authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret)
-       end
-
-       html("Set-Cookie: " .. cookie .. "=" .. authstr .. "; HttpOnly")
-       if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
-               html("; secure")
-       end
-       html("\n")
-end

 
 --
 --
 
 --
 --

--- Wrapper around filter API follows below, exposing the http table, the cgit table, and the post table to the above functions.
+-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.

 --
 --
 
 --
 --
 


@@ -177,12 +128,7 @@ function filter_open(...)
        cgit["repo"] = select(9, ...)
        cgit["page"] = select(10, ...)
        cgit["url"] = select(11, ...)
        cgit["repo"] = select(9, ...)
        cgit["page"] = select(10, ...)
        cgit["url"] = select(11, ...)

-
-       cgit["login"] = ""
-       for _ in cgit["url"]:gfind("/") do
-               cgit["login"] = cgit["login"] .. "../"
-       end
-       cgit["login"] = cgit["login"] .. "?p=login"
+       cgit["login"] = select(12, ...)

 
 end
 
 
 end
 


@@ -197,7 +143,7 @@ end
 
 --
 --
 
 --
 --

--- Utility functions follow below, based on keplerproject/wsapi.
+-- Utility functions based on keplerproject/wsapi.

 --
 --
 
 --
 --
 


@@ -211,6 +157,16 @@ function url_decode(str)
        return str
 end
 
        return str
 end
 

+function url_encode(str)
+       if not str then
+               return ""
+       end
+       str = string.gsub(str, "\n", "\r\n")
+       str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
+       str = string.gsub(str, " ", "+")
+       return str
+end
+

 function parse_qs(qs)
        local tab = {}
        for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
 function parse_qs(qs)
        local tab = {}
        for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do


@@ -223,3 +179,129 @@ function get_cookie(cookies, name)
        cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
        return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
 end
        cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
        return url_decode(string.match(cookies, ";" .. name .. "=(.-);"))
 end

+
+
+--
+--
+-- Cookie construction and validation helpers.
+--
+--
+
+local secret = nil
+
+-- Loads a secret from a file, creates a secret, or returns one from memory.
+function get_secret()
+       if secret ~= nil then
+               return secret
+       end
+       local secret_file = io.open(secret_filename, "r")
+       if secret_file == nil then
+               local old_umask = sysstat.umask(63)
+               local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
+               local temporary_file = io.open(temporary_filename, "w")
+               if temporary_file == nil then
+                       os.exit(177)
+               end
+               temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
+               temporary_file:close()
+               unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
+               unistd.unlink(temporary_filename)
+               sysstat.umask(old_umask)
+               secret_file = io.open(secret_filename, "r")
+       end
+       if secret_file == nil then
+               os.exit(177)
+       end
+       secret = secret_file:read()
+       secret_file:close()
+       if secret:len() ~= 64 then
+               os.exit(177)
+       end
+       return secret
+end
+
+-- Returns value of cookie if cookie is valid. Otherwise returns nil.
+function validate_value(expected_field, cookie)
+       local i = 0
+       local value = ""
+       local field = ""
+       local expiration = 0
+       local salt = ""
+       local hmac = ""
+
+       if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
+               return nil
+       end
+
+       for component in string.gmatch(cookie, "[^|]+") do
+               if i == 0 then
+                       field = component
+               elseif i == 1 then
+                       value = component
+               elseif i == 2 then
+                       expiration = tonumber(component)
+                       if expiration == nil then
+                               expiration = -1
+                       end
+               elseif i == 3 then
+                       salt = component
+               elseif i == 4 then
+                       hmac = component
+               else
+                       break
+               end
+               i = i + 1
+       end
+
+       if hmac == nil or hmac:len() == 0 then
+               return nil
+       end
+
+       -- Lua hashes strings, so these comparisons are time invariant.
+       if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
+               return nil
+       end
+
+       if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
+               return nil
+       end
+
+       if url_decode(field) ~= expected_field then
+               return nil
+       end
+
+       return url_decode(value)
+end
+
+function secure_value(field, value, expiration)
+       if value == nil or value:len() <= 0 then
+               return ""
+       end
+
+       local authstr = ""
+       local salt = crypto.hex(crypto.rand.bytes(16))
+       value = url_encode(value)
+       field = url_encode(field)
+       authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
+       authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
+       return authstr
+end
+
+function set_cookie(cookie, value)
+       html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
+       if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
+               html("; secure")
+       end
+       html("\n")
+end
+
+function redirect_to(url)
+       html("Status: 302 Redirect\n")
+       html("Cache-Control: no-cache, no-store\n")
+       html("Location: " .. url .. "\n")
+end
+
+function not_found()
+       html("Status: 404 Not Found\n")
+       html("Cache-Control: no-cache, no-store\n\n")
+end