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+-- This script may be used with the auth-filter. Be sure to configure it as you wish.
+--
+-- Requirements:
+--      luacrypto >= 0.3
+--      <http://mkottman.github.io/luacrypto/>
+--      lualdap >= 1.2
+--      <http://git.zx2c4.com/lualdap/about/>
+--
+
+
+--
+--
+-- Configure these variables for your settings.
+--
+--
+
+-- A list of password protected repositories, with which gentooAccess
+-- group is allowed to access each one.
+local protected_repos = {
+        glouglou = "infra",
+        portage = "dev"
+}
+
+
+-- 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"
+
+
+
+--
+--
+-- Authentication functions follow below. Swap these out if you want different authentication semantics.
+--
+--
+
+-- Sets HTTP cookie headers based on post and sets up redirection.
+function authenticate_post()
+        local redirect = validate_value("redirect", post["redirect"])
+
+        if redirect == nil then
+                not_found()
+                return 0
+        end
+
+        redirect_to(redirect)
+        
+        local groups = gentoo_ldap_user_groups(post["username"], post["password"])
+        if groups == nil then
+                set_cookie("cgitauth", "")
+        else
+                -- One week expiration time
+                set_cookie("cgitauth", secure_value("gentoogroups", table.concat(groups, ","), os.time() + 604800))
+        end
+
+        html("\n")
+        return 0
+end
+
+
+-- Returns 1 if the cookie is valid and 0 if it is not.
+function authenticate_cookie()
+        local required_group = protected_repos[cgit["repo"]]
+        if required_group == nil then
+                -- We return as valid if the repo is not protected.
+                return 1
+        end
+        
+        local user_groups = validate_value("gentoogroups", get_cookie(http["cookie"], "cgitauth"))
+        if user_groups == nil or user_groups == "" then
+                return 0
+        end
+        for group in string.gmatch(user_groups, "[^,]+") do
+                if group == required_group then
+                        return 1
+                end
+        end
+        return 0
+end
+
+-- Prints the html for the login form.
+function body()
+        html("<h2>Gentoo LDAP Authentication Required</h2>")
+        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("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
+        html("</table></form>")
+
+        return 0
+end
+
+--
+--
+-- Gentoo LDAP support.
+--
+--
+
+local lualdap = require("lualdap")
+
+function gentoo_ldap_user_groups(username, password)
+        -- Ensure the user is alphanumeric
+        if username:match("%W") then
+                return nil
+        end
+
+        local who = "uid=" .. username .. ",ou=devs,dc=gentoo,dc=org"
+
+        local ldap, err = lualdap.open_simple {
+                uri = "ldap://ldap1.gentoo.org",
+                who = who,
+                password = password,
+                starttls = true,
+                certfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.crt",
+                keyfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.key",
+                cacertfile = "/var/www/uwsgi/cgit/gentoo-ldap/ca.pem"
+        }
+        if ldap == nil then
+                return nil
+        end
+
+        local group_suffix = ".group"
+        local group_suffix_len = group_suffix:len()
+        local groups = {}
+        for dn, attribs in ldap:search { base = who, scope = "subtree" } do
+                local access = attribs["gentooAccess"]
+                if dn == who and access ~= nil then
+                        for i, v in ipairs(access) do
+                                local vlen = v:len()
+                                if vlen > group_suffix_len and v:sub(-group_suffix_len) == group_suffix then
+                                        table.insert(groups, v:sub(1, vlen - group_suffix_len))
+                                end
+                        end
+                end
+        end
+
+        ldap:close()
+
+        return groups
+end
+
+--
+--
+-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
+--
+--
+
+local actions = {}
+actions["authenticate-post"] = authenticate_post
+actions["authenticate-cookie"] = authenticate_cookie
+actions["body"] = body
+
+function filter_open(...)
+        action = actions[select(1, ...)]
+
+        http = {}
+        http["cookie"] = select(2, ...)
+        http["method"] = select(3, ...)
+        http["query"] = select(4, ...)
+        http["referer"] = select(5, ...)
+        http["path"] = select(6, ...)
+        http["host"] = select(7, ...)
+        http["https"] = select(8, ...)
+
+        cgit = {}
+        cgit["repo"] = select(9, ...)
+        cgit["page"] = select(10, ...)
+        cgit["url"] = select(11, ...)
+        cgit["login"] = select(12, ...)
+
+end
+
+function filter_close()
+        return action()
+end
+
+function filter_write(str)
+        post = parse_qs(str)
+end
+
+
+--
+--
+-- Utility functions based on keplerproject/wsapi.
+--
+--
+
+function url_decode(str)
+        if not str then
+                return ""
+        end
+        str = string.gsub(str, "+", " ")
+        str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
+        str = string.gsub(str, "\r\n", "\n")
+        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
+                tab[url_decode(key)] = url_decode(val)
+        end
+        return tab
+end
+
+function get_cookie(cookies, name)
+        cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
+        return string.match(cookies, ";" .. name .. "=(.-);")
+end
+
+
+--
+--
+-- Cookie construction and validation helpers.
+--
+--
+
+local crypto = require("crypto")
+
+-- 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("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
+
+        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("sha1", authstr, 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