filters/gentoo-ldap-authentication.lua

   1 -- This script may be used with the auth-filter. Be sure to configure it as you wish.
   2 --
   3 -- Requirements:
   4 --      luacrypto >= 0.3
   5 --      <http://mkottman.github.io/luacrypto/>
   6 --      lualdap >= 1.2
   7 --      <https://git.zx2c4.com/lualdap/about/>
   8 --      luaposix
   9 --      <https://github.com/luaposix/luaposix>
  10 --
  11 local sysstat = require("posix.sys.stat")
  12 local unistd = require("posix.unistd")
  13 local crypto = require("crypto")
  14 local lualdap = require("lualdap")
  15
  16
  17 --
  18 --
  19 -- Configure these variables for your settings.
  20 --
  21 --
  22
  23 -- A list of password protected repositories, with which gentooAccess
  24 -- group is allowed to access each one.
  25 local protected_repos = {
  26         glouglou = "infra",
  27         portage = "dev"
  28 }
  29
  30 -- Set this to a path this script can write to for storing a persistent
  31 -- cookie secret, which should be guarded.
  32 local secret_filename = "/var/cache/cgit/auth-secret"
  33
  34
  35 --
  36 --
  37 -- Authentication functions follow below. Swap these out if you want different authentication semantics.
  38 --
  39 --
  40
  41 -- Sets HTTP cookie headers based on post and sets up redirection.
  42 function authenticate_post()
  43         local redirect = validate_value("redirect", post["redirect"])
  44
  45         if redirect == nil then
  46                 not_found()
  47                 return 0
  48         end
  49
  50         redirect_to(redirect)
  51
  52         local groups = gentoo_ldap_user_groups(post["username"], post["password"])
  53         if groups == nil then
  54                 set_cookie("cgitauth", "")
  55         else
  56                 -- One week expiration time
  57                 set_cookie("cgitauth", secure_value("gentoogroups", table.concat(groups, ","), os.time() + 604800))
  58         end
  59
  60         html("\n")
  61         return 0
  62 end
  63
  64
  65 -- Returns 1 if the cookie is valid and 0 if it is not.
  66 function authenticate_cookie()
  67         local required_group = protected_repos[cgit["repo"]]
  68         if required_group == nil then
  69                 -- We return as valid if the repo is not protected.
  70                 return 1
  71         end
  72
  73         local user_groups = validate_value("gentoogroups", get_cookie(http["cookie"], "cgitauth"))
  74         if user_groups == nil or user_groups == "" then
  75                 return 0
  76         end
  77         for group in string.gmatch(user_groups, "[^,]+") do
  78                 if group == required_group then
  79                         return 1
  80                 end
  81         end
  82         return 0
  83 end
  84
  85 -- Prints the html for the login form.
  86 function body()
  87         html("<h2>Gentoo LDAP Authentication Required</h2>")
  88         html("<form method='post' action='")
  89         html_attr(cgit["login"])
  90         html("'>")
  91         html("<input type='hidden' name='redirect' value='")
  92         html_attr(secure_value("redirect", cgit["url"], 0))
  93         html("' />")
  94         html("<table>")
  95         html("<tr><td><label for='username'>Username:</label></td><td><input id='username' name='username' autofocus /></td></tr>")
  96         html("<tr><td><label for='password'>Password:</label></td><td><input id='password' name='password' type='password' /></td></tr>")
  97         html("<tr><td colspan='2'><input value='Login' type='submit' /></td></tr>")
  98         html("</table></form>")
  99
 100         return 0
 101 end
 102
 103 --
 104 --
 105 -- Gentoo LDAP support.
 106 --
 107 --
 108
 109 function gentoo_ldap_user_groups(username, password)
 110         -- Ensure the user is alphanumeric
 111         if username == nil or username:match("%W") then
 112                 return nil
 113         end
 114
 115         local who = "uid=" .. username .. ",ou=devs,dc=gentoo,dc=org"
 116
 117         local ldap, err = lualdap.open_simple {
 118                 uri = "ldap://ldap1.gentoo.org",
 119                 who = who,
 120                 password = password,
 121                 starttls = true,
 122                 certfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.crt",
 123                 keyfile = "/var/www/uwsgi/cgit/gentoo-ldap/star.gentoo.org.key",
 124                 cacertfile = "/var/www/uwsgi/cgit/gentoo-ldap/ca.pem"
 125         }
 126         if ldap == nil then
 127                 return nil
 128         end
 129
 130         local group_suffix = ".group"
 131         local group_suffix_len = group_suffix:len()
 132         local groups = {}
 133         for dn, attribs in ldap:search { base = who, scope = "subtree" } do
 134                 local access = attribs["gentooAccess"]
 135                 if dn == who and access ~= nil then
 136                         for i, v in ipairs(access) do
 137                                 local vlen = v:len()
 138                                 if vlen > group_suffix_len and v:sub(-group_suffix_len) == group_suffix then
 139                                         table.insert(groups, v:sub(1, vlen - group_suffix_len))
 140                                 end
 141                         end
 142                 end
 143         end
 144
 145         ldap:close()
 146
 147         return groups
 148 end
 149
 150 --
 151 --
 152 -- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
 153 --
 154 --
 155
 156 local actions = {}
 157 actions["authenticate-post"] = authenticate_post
 158 actions["authenticate-cookie"] = authenticate_cookie
 159 actions["body"] = body
 160
 161 function filter_open(...)
 162         action = actions[select(1, ...)]
 163
 164         http = {}
 165         http["cookie"] = select(2, ...)
 166         http["method"] = select(3, ...)
 167         http["query"] = select(4, ...)
 168         http["referer"] = select(5, ...)
 169         http["path"] = select(6, ...)
 170         http["host"] = select(7, ...)
 171         http["https"] = select(8, ...)
 172
 173         cgit = {}
 174         cgit["repo"] = select(9, ...)
 175         cgit["page"] = select(10, ...)
 176         cgit["url"] = select(11, ...)
 177         cgit["login"] = select(12, ...)
 178
 179 end
 180
 181 function filter_close()
 182         return action()
 183 end
 184
 185 function filter_write(str)
 186         post = parse_qs(str)
 187 end
 188
 189
 190 --
 191 --
 192 -- Utility functions based on keplerproject/wsapi.
 193 --
 194 --
 195
 196 function url_decode(str)
 197         if not str then
 198                 return ""
 199         end
 200         str = string.gsub(str, "+", " ")
 201         str = string.gsub(str, "%%(%x%x)", function(h) return string.char(tonumber(h, 16)) end)
 202         str = string.gsub(str, "\r\n", "\n")
 203         return str
 204 end
 205
 206 function url_encode(str)
 207         if not str then
 208                 return ""
 209         end
 210         str = string.gsub(str, "\n", "\r\n")
 211         str = string.gsub(str, "([^%w ])", function(c) return string.format("%%%02X", string.byte(c)) end)
 212         str = string.gsub(str, " ", "+")
 213         return str
 214 end
 215
 216 function parse_qs(qs)
 217         local tab = {}
 218         for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do
 219                 tab[url_decode(key)] = url_decode(val)
 220         end
 221         return tab
 222 end
 223
 224 function get_cookie(cookies, name)
 225         cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
 226         return string.match(cookies, ";" .. name .. "=(.-);")
 227 end
 228
 229
 230 --
 231 --
 232 -- Cookie construction and validation helpers.
 233 --
 234 --
 235
 236 local secret = nil
 237
 238 -- Loads a secret from a file, creates a secret, or returns one from memory.
 239 function get_secret()
 240         if secret ~= nil then
 241                 return secret
 242         end
 243         local secret_file = io.open(secret_filename, "r")
 244         if secret_file == nil then
 245                 local old_umask = sysstat.umask(63)
 246                 local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
 247                 local temporary_file = io.open(temporary_filename, "w")
 248                 if temporary_file == nil then
 249                         os.exit(177)
 250                 end
 251                 temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
 252                 temporary_file:close()
 253                 unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
 254                 unistd.unlink(temporary_filename)
 255                 sysstat.umask(old_umask)
 256                 secret_file = io.open(secret_filename, "r")
 257         end
 258         if secret_file == nil then
 259                 os.exit(177)
 260         end
 261         secret = secret_file:read()
 262         secret_file:close()
 263         if secret:len() ~= 64 then
 264                 os.exit(177)
 265         end
 266         return secret
 267 end
 268
 269 -- Returns value of cookie if cookie is valid. Otherwise returns nil.
 270 function validate_value(expected_field, cookie)
 271         local i = 0
 272         local value = ""
 273         local field = ""
 274         local expiration = 0
 275         local salt = ""
 276         local hmac = ""
 277
 278         if cookie == nil or cookie:len() < 3 or cookie:sub(1, 1) == "|" then
 279                 return nil
 280         end
 281
 282         for component in string.gmatch(cookie, "[^|]+") do
 283                 if i == 0 then
 284                         field = component
 285                 elseif i == 1 then
 286                         value = component
 287                 elseif i == 2 then
 288                         expiration = tonumber(component)
 289                         if expiration == nil then
 290                                 expiration = -1
 291                         end
 292                 elseif i == 3 then
 293                         salt = component
 294                 elseif i == 4 then
 295                         hmac = component
 296                 else
 297                         break
 298                 end
 299                 i = i + 1
 300         end
 301
 302         if hmac == nil or hmac:len() == 0 then
 303                 return nil
 304         end
 305
 306         -- Lua hashes strings, so these comparisons are time invariant.
 307         if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
 308                 return nil
 309         end
 310
 311         if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then
 312                 return nil
 313         end
 314
 315         if url_decode(field) ~= expected_field then
 316                 return nil
 317         end
 318
 319         return url_decode(value)
 320 end
 321
 322 function secure_value(field, value, expiration)
 323         if value == nil or value:len() <= 0 then
 324                 return ""
 325         end
 326
 327         local authstr = ""
 328         local salt = crypto.hex(crypto.rand.bytes(16))
 329         value = url_encode(value)
 330         field = url_encode(field)
 331         authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
 332         authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
 333         return authstr
 334 end
 335
 336 function set_cookie(cookie, value)
 337         html("Set-Cookie: " .. cookie .. "=" .. value .. "; HttpOnly")
 338         if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
 339                 html("; secure")
 340         end
 341         html("\n")
 342 end
 343
 344 function redirect_to(url)
 345         html("Status: 302 Redirect\n")
 346         html("Cache-Control: no-cache, no-store\n")
 347         html("Location: " .. url .. "\n")
 348 end
 349
 350 function not_found()
 351         html("Status: 404 Not Found\n")
 352         html("Cache-Control: no-cache, no-store\n\n")
 353 end