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

diff --git a/filters/simple-authentication.lua b/filters/simple-authentication.lua
index 5935d080f87e0388a2dfdcf9b8b1586f93c186d5..de34d092135d0db24b6a7057c00e3293e9fffe2c 100644 (file)
--- a/filters/simple-authentication.lua
+++ b/filters/simple-authentication.lua
@@ -12,17 +12,27 @@
 --
 --
 
 --
 --
 

+-- 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 }
 }
 

+-- Please note that, in production, you'll want to replace this simple lookup
+-- table with either a table of salted and hashed passwords (using something
+-- smart like scrypt), or replace this table lookup with an external support,
+-- such as consulting your system's pam / shadow system, or an external
+-- database, or an external validating web service. For testing, or for
+-- extremely low-security usage, you may be able, however, to get away with
+-- compromising on hardcoding the passwords in cleartext, as we have done here.

 local users = {
        jason           = "secretpassword",
        laurent         = "s3cr3t",
        bob             = "ilikelua"
 }
 
 local users = {
        jason           = "secretpassword",
        laurent         = "s3cr3t",
        bob             = "ilikelua"
 }
 

+-- All cookies will be authenticated based on this secret. Make it something
+-- totally random and impossible to guess. It should be large.

 local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
 
 
 local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
 
 


@@ -36,7 +46,7 @@ local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
 -- Sets HTTP cookie headers based on post and sets up redirection.
 function authenticate_post()
        local password = users[post["username"]]
 -- Sets HTTP cookie headers based on post and sets up redirection.
 function authenticate_post()
        local password = users[post["username"]]

-       local redirect = validate_value(post["redirect"])
+       local redirect = validate_value("redirect", post["redirect"])

 
        if redirect == nil then
                not_found()
 
        if redirect == nil then
                not_found()


@@ -45,12 +55,12 @@ function authenticate_post()
 
        redirect_to(redirect)
 
 
        redirect_to(redirect)
 

-       -- TODO: Implement time invariant string comparison function to mitigate timing attack.
+       -- Lua hashes strings, so these comparisons are time invariant.

        if password == nil or password ~= post["password"] then
                set_cookie("cgitauth", "")
        else
                -- One week expiration time
        if password == nil or password ~= post["password"] then
                set_cookie("cgitauth", "")
        else
                -- One week expiration time

-               local username = secure_value(post["username"], os.time() + 604800)
+               local username = secure_value("username", post["username"], os.time() + 604800)

                set_cookie("cgitauth", username)
        end
 
                set_cookie("cgitauth", username)
        end
 


@@ -67,7 +77,7 @@ function authenticate_cookie()
                return 1
        end
 
                return 1
        end
 

-       local username = validate_value(get_cookie(http["cookie"], "cgitauth"))
+       local username = validate_value("username", get_cookie(http["cookie"], "cgitauth"))

        if username == nil or not accepted_users[username:lower()] then
                return 0
        else
        if username == nil or not accepted_users[username:lower()] then
                return 0
        else


@@ -82,7 +92,7 @@ function body()
        html_attr(cgit["login"])
        html("'>")
        html("<input type='hidden' name='redirect' value='")
        html_attr(cgit["login"])
        html("'>")
        html("<input type='hidden' name='redirect' value='")

-       html_attr(secure_value(cgit["url"], 0))
+       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("' />")
        html("<table>")
        html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")


@@ -122,12 +132,7 @@ 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
 


@@ -161,7 +166,7 @@ function url_encode(str)
                return ""
        end
        str = string.gsub(str, "\n", "\r\n")
                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, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)

        str = string.gsub(str, " ", "+")
        return str
 end
        str = string.gsub(str, " ", "+")
        return str
 end


@@ -189,9 +194,10 @@ end
 local crypto = require("crypto")
 
 -- Returns value of cookie if cookie is valid. Otherwise returns nil.
 local crypto = require("crypto")
 
 -- Returns value of cookie if cookie is valid. Otherwise returns nil.

-function validate_value(cookie)
+function validate_value(expected_field, cookie)

        local i = 0
        local value = ""
        local i = 0
        local value = ""

+       local field = ""

        local expiration = 0
        local salt = ""
        local hmac = ""
        local expiration = 0
        local salt = ""
        local hmac = ""


@@ -202,15 +208,17 @@ function validate_value(cookie)
 
        for component in string.gmatch(cookie, "[^|]+") do
                if i == 0 then
 
        for component in string.gmatch(cookie, "[^|]+") do
                if i == 0 then

-                       value = component
+                       field = component

                elseif i == 1 then
                elseif i == 1 then

+                       value = component
+               elseif i == 2 then

                        expiration = tonumber(component)
                        if expiration == nil then
                        expiration = tonumber(component)
                        if expiration == nil then

-                               expiration = 0
+                               expiration = -1

                        end
                        end

-               elseif i == 2 then
-                       salt = component

                elseif i == 3 then
                elseif i == 3 then

+                       salt = component
+               elseif i == 4 then

                        hmac = component
                else
                        break
                        hmac = component
                else
                        break


@@ -222,19 +230,23 @@ function validate_value(cookie)
                return nil
        end
 
                return nil
        end
 

-       -- TODO: implement time invariant comparison to prevent against timing attack.
-       if hmac ~= crypto.hmac.digest("sha1", value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
+       -- Lua hashes strings, so these comparisons are time invariant.
+       if hmac ~= crypto.hmac.digest("sha1", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
+               return nil
+       end
+
+       if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then

                return nil
        end
 
                return nil
        end
 

-       if expiration ~= 0 and expiration <= os.time() then
+       if url_decode(field) ~= expected_field then

                return nil
        end
 
        return url_decode(value)
 end
 
                return nil
        end
 
        return url_decode(value)
 end
 

-function secure_value(value, expiration)
+function secure_value(field, value, expiration)

        if value == nil or value:len() <= 0 then
                return ""
        end
        if value == nil or value:len() <= 0 then
                return ""
        end


@@ -242,7 +254,8 @@ function secure_value(value, expiration)
        local authstr = ""
        local salt = crypto.hex(crypto.rand.bytes(16))
        value = url_encode(value)
        local authstr = ""
        local salt = crypto.hex(crypto.rand.bytes(16))
        value = url_encode(value)

-       authstr = value .. "|" .. tostring(expiration) .. "|" .. salt
+       field = url_encode(field)
+       authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt

        authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret)
        return authstr
 end
        authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret)
        return authstr
 end