authentication: use hidden form instead of referer
This also gives us some CSRF protection. Note that we make use of the hmac to protect the redirect value. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld
부모
d6e9200cc3
커밋
b826537cb4
22
cgit.c
22
cgit.c
@ -614,22 +614,19 @@ static inline void open_auth_filter(struct cgit_context *ctx, const char *functi
|
||||
ctx->qry.url ? ctx->qry.url : "");
|
||||
}
|
||||
|
||||
/* We intentionally keep this rather small, instead of looping and
|
||||
* feeding it to the filter a couple bytes at a time. This way, the
|
||||
* filter itself does not need to handle any denial of service or
|
||||
* buffer bloat issues. If this winds up being too small, people
|
||||
* will complain on the mailing list, and we'll increase it as needed. */
|
||||
#define MAX_AUTHENTICATION_POST_BYTES 4096
|
||||
/* The filter is expected to spit out "Status: " and all headers. */
|
||||
static inline void authenticate_post(struct cgit_context *ctx)
|
||||
{
|
||||
if (ctx->env.http_referer && strlen(ctx->env.http_referer) > 0) {
|
||||
html("Status: 302 Redirect\n");
|
||||
html("Cache-Control: no-cache, no-store\n");
|
||||
htmlf("Location: %s\n", ctx->env.http_referer);
|
||||
} else {
|
||||
html("Status: 501 Missing Referer\n");
|
||||
html("Cache-Control: no-cache, no-store\n\n");
|
||||
exit(0);
|
||||
}
|
||||
|
||||
open_auth_filter(ctx, "authenticate-post");
|
||||
char buffer[MAX_AUTHENTICATION_POST_BYTES];
|
||||
int len;
|
||||
|
||||
open_auth_filter(ctx, "authenticate-post");
|
||||
len = ctx->env.content_length;
|
||||
if (len > MAX_AUTHENTICATION_POST_BYTES)
|
||||
len = MAX_AUTHENTICATION_POST_BYTES;
|
||||
@ -637,10 +634,7 @@ static inline void authenticate_post(struct cgit_context *ctx)
|
||||
die_errno("Could not read POST from stdin");
|
||||
if (write(STDOUT_FILENO, buffer, len) < 0)
|
||||
die_errno("Could not write POST to stdout");
|
||||
/* The filter may now spit out a Set-Cookie: ... */
|
||||
cgit_close_filter(ctx->cfg.auth_filter);
|
||||
|
||||
html("\n");
|
||||
exit(0);
|
||||
}
|
||||
|
||||
|
||||
@ -662,7 +662,8 @@ auth filter::
|
||||
the http cookie and return a 0 if it is invalid or 1 if it is invalid,
|
||||
in the exit code / close function. If the filter action is
|
||||
"authenticate-post", this filter receives POST'd parameters on
|
||||
standard input, and should write to output one or more "Set-Cookie"
|
||||
standard input, and should write a complete CGI request, preferably
|
||||
with a 302 redirect, and write to output one or more "Set-Cookie"
|
||||
HTTP headers, each followed by a newline.
|
||||
|
||||
Please see `filters/simple-authentication.lua` for a clear example
|
||||
|
||||
@ -33,15 +33,28 @@ local secret = "BE SURE TO CUSTOMIZE THIS STRING TO SOMETHING BIG AND RANDOM"
|
||||
--
|
||||
--
|
||||
|
||||
-- Sets HTTP cookie headers based on post
|
||||
-- Sets HTTP cookie headers based on post and sets up redirection.
|
||||
function authenticate_post()
|
||||
local password = users[post["username"]]
|
||||
-- TODO: Implement time invariant string comparison function to mitigate against timing attack.
|
||||
if password == nil or password ~= post["password"] then
|
||||
construct_cookie("", "cgitauth")
|
||||
else
|
||||
construct_cookie(post["username"], "cgitauth")
|
||||
local redirect = validate_value(post["redirect"])
|
||||
|
||||
if redirect == nil then
|
||||
not_found()
|
||||
return 0
|
||||
end
|
||||
|
||||
redirect_to(redirect)
|
||||
|
||||
-- TODO: Implement time invariant string comparison function to mitigate timing attack.
|
||||
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)
|
||||
set_cookie("cgitauth", username)
|
||||
end
|
||||
|
||||
html("\n")
|
||||
return 0
|
||||
end
|
||||
|
||||
@ -54,8 +67,8 @@ function authenticate_cookie()
|
||||
return 1
|
||||
end
|
||||
|
||||
local username = validate_cookie(get_cookie(http["cookie"], "cgitauth"))
|
||||
if username == nil or not accepted_users[username] then
|
||||
local username = validate_value(get_cookie(http["cookie"], "cgitauth"))
|
||||
if username == nil or not accepted_users[username:lower()] then
|
||||
return 0
|
||||
else
|
||||
return 1
|
||||
@ -68,6 +81,9 @@ function body()
|
||||
html("<form method='post' action='")
|
||||
html_attr(cgit["login"])
|
||||
html("'>")
|
||||
html("<input type='hidden' name='redirect' value='")
|
||||
html_attr(secure_value(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>")
|
||||
@ -78,81 +94,10 @@ function body()
|
||||
end
|
||||
|
||||
|
||||
--
|
||||
--
|
||||
-- Cookie construction and validation helpers.
|
||||
--
|
||||
--
|
||||
|
||||
local crypto = require("crypto")
|
||||
|
||||
-- Returns username of cookie if cookie is valid. Otherwise returns nil.
|
||||
function validate_cookie(cookie)
|
||||
local i = 0
|
||||
local username = ""
|
||||
local expiration = 0
|
||||
local salt = ""
|
||||
local hmac = ""
|
||||
|
||||
if cookie:len() < 3 or cookie:sub(1, 1) == "|" then
|
||||
return nil
|
||||
end
|
||||
|
||||
for component in string.gmatch(cookie, "[^|]+") do
|
||||
if i == 0 then
|
||||
username = component
|
||||
elseif i == 1 then
|
||||
expiration = tonumber(component)
|
||||
if expiration == nil then
|
||||
expiration = 0
|
||||
end
|
||||
elseif i == 2 then
|
||||
salt = component
|
||||
elseif i == 3 then
|
||||
hmac = component
|
||||
else
|
||||
break
|
||||
end
|
||||
i = i + 1
|
||||
end
|
||||
|
||||
if hmac == nil or hmac:len() == 0 then
|
||||
return nil
|
||||
end
|
||||
|
||||
-- TODO: implement time invariant comparison to prevent against timing attack.
|
||||
if hmac ~= crypto.hmac.digest("sha1", username .. "|" .. tostring(expiration) .. "|" .. salt, secret) then
|
||||
return nil
|
||||
end
|
||||
|
||||
if expiration <= os.time() then
|
||||
return nil
|
||||
end
|
||||
|
||||
return username:lower()
|
||||
end
|
||||
|
||||
function construct_cookie(username, cookie)
|
||||
local authstr = ""
|
||||
if username:len() > 0 then
|
||||
-- One week expiration time
|
||||
local expiration = os.time() + 604800
|
||||
local salt = crypto.hex(crypto.rand.bytes(16))
|
||||
|
||||
authstr = username .. "|" .. tostring(expiration) .. "|" .. salt
|
||||
authstr = authstr .. "|" .. crypto.hmac.digest("sha1", authstr, secret)
|
||||
end
|
||||
|
||||
html("Set-Cookie: " .. cookie .. "=" .. authstr .. "; HttpOnly")
|
||||
if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then
|
||||
html("; secure")
|
||||
end
|
||||
html("\n")
|
||||
end
|
||||
|
||||
--
|
||||
--
|
||||
-- Wrapper around filter API follows below, exposing the http table, the cgit table, and the post table to the above functions.
|
||||
-- Wrapper around filter API, exposing the http table, the cgit table, and the post table to the above functions.
|
||||
--
|
||||
--
|
||||
|
||||
@ -197,7 +142,7 @@ end
|
||||
|
||||
--
|
||||
--
|
||||
-- Utility functions follow below, based on keplerproject/wsapi.
|
||||
-- Utility functions based on keplerproject/wsapi.
|
||||
--
|
||||
--
|
||||
|
||||
@ -211,6 +156,16 @@ function url_decode(str)
|
||||
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
|
||||
@ -223,3 +178,90 @@ function get_cookie(cookies, name)
|
||||
cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";")
|
||||
return url_decode(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(cookie)
|
||||
local i = 0
|
||||
local value = ""
|
||||
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
|
||||
value = component
|
||||
elseif i == 1 then
|
||||
expiration = tonumber(component)
|
||||
if expiration == nil then
|
||||
expiration = 0
|
||||
end
|
||||
elseif i == 2 then
|
||||
salt = component
|
||||
elseif i == 3 then
|
||||
hmac = component
|
||||
else
|
||||
break
|
||||
end
|
||||
i = i + 1
|
||||
end
|
||||
|
||||
if hmac == nil or hmac:len() == 0 then
|
||||
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
|
||||
return nil
|
||||
end
|
||||
|
||||
if expiration ~= 0 and expiration <= os.time() then
|
||||
return nil
|
||||
end
|
||||
|
||||
return url_decode(value)
|
||||
end
|
||||
|
||||
function secure_value(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)
|
||||
authstr = 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
|
||||
|
||||
불러오는 중...
Reference in New Issue
Block a user