auth-filters: generate secret securely
This is much better than having the user generate it themselves. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Jason A. Donenfeld
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c4d23d02ec
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b73df8098f
@ -5,7 +5,13 @@
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-- <http://mkottman.github.io/luacrypto/>
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-- lualdap >= 1.2
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-- <https://git.zx2c4.com/lualdap/about/>
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-- luaposix
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-- <https://github.com/luaposix/luaposix>
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--
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local sysstat = require("posix.sys.stat")
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local unistd = require("posix.unistd")
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local crypto = require("crypto")
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local lualdap = require("lualdap")
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--
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@ -21,11 +27,9 @@ local protected_repos = {
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portage = "dev"
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}
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-- All cookies will be authenticated based on this secret. Make it something
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-- totally random and impossible to guess. It should be large.
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local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
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-- Set this to a path this script can write to for storing a persistent
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-- cookie secret, which should be guarded.
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local secret_filename = "/var/cache/cgit/auth-secret"
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--
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@ -102,8 +106,6 @@ end
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--
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--
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local lualdap = require("lualdap")
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function gentoo_ldap_user_groups(username, password)
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-- Ensure the user is alphanumeric
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if username == nil or username:match("%W") then
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@ -231,7 +233,38 @@ end
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--
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--
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local crypto = require("crypto")
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local secret = nil
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-- Loads a secret from a file, creates a secret, or returns one from memory.
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function get_secret()
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if secret ~= nil then
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return secret
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end
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local secret_file = io.open(secret_filename, "r")
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if secret_file == nil then
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local old_umask = sysstat.umask(63)
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local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
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local temporary_file = io.open(temporary_filename, "w")
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if temporary_file == nil then
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os.exit(177)
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end
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temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
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temporary_file:close()
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unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
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unistd.unlink(temporary_filename)
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sysstat.umask(old_umask)
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secret_file = io.open(secret_filename, "r")
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end
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if secret_file == nil then
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os.exit(177)
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end
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secret = secret_file:read()
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secret_file:close()
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if secret:len() ~= 64 then
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os.exit(177)
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end
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return secret
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end
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-- Returns value of cookie if cookie is valid. Otherwise returns nil.
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function validate_value(expected_field, cookie)
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@ -271,7 +304,7 @@ function validate_value(expected_field, cookie)
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end
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-- Lua hashes strings, so these comparisons are time invariant.
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if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
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if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
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return nil
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end
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@ -296,7 +329,7 @@ function secure_value(field, value, expiration)
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value = url_encode(value)
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field = url_encode(field)
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authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
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authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, secret)
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authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
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return authstr
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end
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@ -3,7 +3,12 @@
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-- Requirements:
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-- luacrypto >= 0.3
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-- <http://mkottman.github.io/luacrypto/>
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-- luaposix
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-- <https://github.com/luaposix/luaposix>
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--
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local sysstat = require("posix.sys.stat")
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local unistd = require("posix.unistd")
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local crypto = require("crypto")
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--
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@ -31,11 +36,9 @@ local users = {
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bob = "ilikelua"
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}
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-- All cookies will be authenticated based on this secret. Make it something
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-- totally random and impossible to guess. It should be large.
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local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
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-- Set this to a path this script can write to for storing a persistent
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-- cookie secret, which should be guarded.
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local secret_filename = "/var/cache/cgit/auth-secret"
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--
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--
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@ -191,7 +194,38 @@ end
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--
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--
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local crypto = require("crypto")
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local secret = nil
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-- Loads a secret from a file, creates a secret, or returns one from memory.
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function get_secret()
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if secret ~= nil then
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return secret
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end
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local secret_file = io.open(secret_filename, "r")
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if secret_file == nil then
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local old_umask = sysstat.umask(63)
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local temporary_filename = secret_filename .. ".tmp." .. crypto.hex(crypto.rand.bytes(16))
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local temporary_file = io.open(temporary_filename, "w")
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if temporary_file == nil then
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os.exit(177)
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end
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temporary_file:write(crypto.hex(crypto.rand.bytes(32)))
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temporary_file:close()
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unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same.
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unistd.unlink(temporary_filename)
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sysstat.umask(old_umask)
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secret_file = io.open(secret_filename, "r")
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end
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if secret_file == nil then
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os.exit(177)
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end
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secret = secret_file:read()
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secret_file:close()
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if secret:len() ~= 64 then
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os.exit(177)
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end
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return secret
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end
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-- Returns value of cookie if cookie is valid. Otherwise returns nil.
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function validate_value(expected_field, cookie)
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@ -231,7 +265,7 @@ function validate_value(expected_field, cookie)
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end
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-- Lua hashes strings, so these comparisons are time invariant.
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if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
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if hmac ~= crypto.hmac.digest("sha256", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, get_secret()) then
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return nil
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end
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@ -256,7 +290,7 @@ function secure_value(field, value, expiration)
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value = url_encode(value)
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field = url_encode(field)
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authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt
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authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, secret)
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authstr = authstr .. "|" .. crypto.hmac.digest("sha256", authstr, get_secret())
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return authstr
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end
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