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simple-authentication.lua: tie secure cookies to field names

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This commit is contained in:
Jason A. Donenfeld 2015-03-05 15:45:25 +01:00
parent bd24832cd7
commit ecd6b7230c
1 changed files with 21 additions and 13 deletions
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34
filters/simple-authentication.lua
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@ -46,7 +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"]]
local redirect = validate_value(post["redirect"])
local redirect = validate_value("redirect", post["redirect"])
if redirect == nil then
not_found()
@ -60,7 +60,7 @@ function authenticate_post()
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
@ -77,7 +77,7 @@ function authenticate_cookie()
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
@ -92,7 +92,7 @@ function body()
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>")
@ -194,9 +194,10 @@ end
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 field = ""
local expiration = 0
local salt = ""
local hmac = ""
@ -207,15 +208,17 @@ function validate_value(cookie)
for component in string.gmatch(cookie, "[^|]+") do
if i == 0 then
value = component
field = component
elseif i == 1 then
value = component
elseif i == 2 then
expiration = tonumber(component)
if expiration == nil then
expiration = 0
expiration = -1
end
elseif i == 2 then
salt = component
elseif i == 3 then
salt = component
elseif i == 4 then
hmac = component
else
break
@ -228,18 +231,22 @@ function validate_value(cookie)
end
-- Lua hashes strings, so these comparisons are time invariant.
if hmac ~= crypto.hmac.digest("sha1", value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
if hmac ~= crypto.hmac.digest("sha1", field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
return nil
end
if expiration ~= 0 and expiration <= os.time() then
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(value, expiration)
function secure_value(field, value, expiration)
if value == nil or value:len() <= 0 then
return ""
end
@ -247,7 +254,8 @@ function secure_value(value, expiration)
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