Diff options
Diffstat (limited to 'extensions/auth-file.lua')
| -rw-r--r-- | extensions/auth-file.lua | 532 |
1 file changed, 345 insertions, 187 deletions
diff --git a/extensions/auth-file.lua b/extensions/auth-file.lua index 71c8bc6..5415ca7 100644 --- a/extensions/auth-file.lua +++ b/extensions/auth-file.lua @@ -1,204 +1,203 @@ --- cgit auth-filter that gates repositories behind a login form and a --- signed session cookie. +-- cgit auth-filter that gates repositories behind a login form and a signed +-- session cookie. -- --- This is the FILE-BACKED variant. The user accounts, the groups, and --- the per-repository access lists are read from files on disk. Set their --- paths below and edit those files without touching this script. This --- suits larger or externally managed user sets. +-- This is the FILE-BACKED variant. The user accounts, the groups, and the +-- per-repository access lists are read from files on disk, whose paths are set +-- in the CONFIGURATION block below. Edit those files without touching this +-- script. This suits larger or externally managed user sets. -- --- The companion auth-inline.lua behaves identically but keeps its --- accounts and access lists inline in the script itself, which suits a --- small fixed set of users. +-- The companion auth-inline.lua behaves identically but keeps its accounts and +-- access lists inline in the script itself, which suits a small fixed set of +-- users. -- -- Enable it in cgitrc with --- auth-filter=lua:/path/to/auth-file.lua +-- auth-filter=lua:/path/to/auth-file.lua -- --- Requirements --- luaossl --- <http://25thandclement.com/~william/projects/luaossl.html> --- luaposix --- <https://github.com/luaposix/luaposix> +-- SUPPORTED LUA -- +-- Lua 5.1, 5.2, 5.3, 5.4 and LuaJIT. Lua 5.5 is not supported, because luaossl +-- has no 5.5 build. Match the runtime to the Lua that cgit is built against. +-- +-- HTTPS IS RECOMMENDED +-- +-- Serve cgit over HTTPS. Terminate TLS at the web server in front of cgit. The +-- session cookie is marked Secure by default, so a browser only sends it back +-- over HTTPS. If you genuinely run cgit over plain HTTP with no TLS anywhere, +-- set cookie_insecure below, otherwise the cookie is never returned and login +-- appears to loop. +-- +-- DEPENDENCIES +-- +-- luaossl OpenSSL binding, provides openssl.rand and openssl.hmac +-- <https://github.com/wahern/luaossl> +-- luaposix POSIX binding, provides posix.sys.stat and posix.unistd +-- <https://github.com/luaposix/luaposix> +-- +-- The reliable cross-platform install is LuaRocks, matched to your Lua +-- version. luaossl also needs the OpenSSL development headers present. +-- +-- # Debian and Ubuntu +-- sudo apt install luarocks libssl-dev +-- sudo luarocks --lua-version 5.1 install luaossl +-- sudo luarocks --lua-version 5.1 install luaposix +-- +-- # Fedora +-- sudo dnf install luarocks openssl-devel +-- sudo luarocks --lua-version 5.1 install luaossl luaposix +-- +-- # Alpine +-- sudo apk add luarocks openssl-dev +-- sudo luarocks-5.1 install luaossl luaposix +-- +-- # macOS with Homebrew +-- brew install luarocks openssl +-- luarocks install luaossl OPENSSL_DIR="$(brew --prefix openssl)" +-- luarocks install luaposix +-- +-- Some distributions also package these, for example lua-luaossl and lua-posix +-- on Debian. If you use a distribution package, make sure it is built for the +-- same Lua version as cgit. +-- +-- SECURITY NOTES +-- +-- The cookie carries only a username with no server-side session store, so +-- deleting an account does not revoke a cookie already issued until it +-- expires, and instances that share a secret file accept each other's cookies. +-- The login form carries no CSRF token. Both are acceptable for gating read +-- access to a git browser. Weigh them before guarding anything more sensitive. + local sysstat = require("posix.sys.stat") local unistd = require("posix.unistd") local rand = require("openssl.rand") local hmac = require("openssl.hmac") --- This file should contain a series of lines in the form of: --- username1:hash1 --- username2:hash2 --- username3:hash3 --- ... --- Hashes can be generated using something like `mkpasswd -m sha-512 -R 300000`. +-- +-- ========================= CONFIGURATION ========================= +-- Edit the values in this block. Nothing below it needs changing for +-- ordinary use. +-- + +-- Accounts, one per line, as username:hash. Generate a hash with +-- mkpasswd -m sha-512 -R 300000 -- This file should not be world-readable. local users_filename = "/etc/cgit-auth/users" --- This file should contain a series of lines in the form of: --- groupname1:username1,username2,username3,... --- ... +-- Group membership, one per line, as groupname:user1,user2,user3,... local groups_filename = "/etc/cgit-auth/groups" --- This file should contain a series of lines in the form of: --- reponame1:groupname1,groupname2,groupname3,... --- ... +-- Per-repository access, one per line, as reponame:group1,group2,... +-- A repository listed here is protected. One not listed is public. local repos_filename = "/etc/cgit-auth/repos" --- Set this to a path this script can write to for storing a persistent --- cookie secret, which should not be world-readable. +-- Where the cookie-signing secret is stored. It is created on first use. It +-- must be persistent and writable by cgit. Prefer a path OUTSIDE the cache +-- root, because pruning the cache would delete a secret kept inside it and +-- invalidate every live session. This file should not be world-readable. local secret_filename = "/var/cache/cgit/auth-secret" +-- How long a login stays valid, in seconds. Default one week. +local session_seconds = 7 * 24 * 60 * 60 + +-- Name of the session cookie. +local cookie_name = "cgitauth" + +-- Path the cookie is scoped to. "/" covers the whole host. Set it to the cgit +-- root to scope the cookie more tightly. +local cookie_path = "/" + +-- Leave false so the cookie is marked Secure and only travels over HTTPS. Set +-- it true ONLY if cgit is served over plain HTTP with no TLS anywhere, see the +-- HTTPS note in the header. +local cookie_insecure = false + +-- +-- ================================================================= +-- + +-- A throwaway hash of the documented shape, used only to spend the same work +-- on a missing account as on a present one, so a failed login does not reveal +-- by timing whether the username exists. +local dummy_hash = "$6$rounds=300000$0000000000000000$" + +-- Module state shared across the open, write and close calls of one request. +local action, http, cgit, post + -- -- --- Authentication functions follow below. Swap these out if you want different authentication semantics. +-- Account and access-list storage. This is the ONLY part that differs from +-- auth-inline.lua. Swap these two functions to change where accounts live. -- -- --- Looks up a hash for a given user. -function lookup_hash(user) - local line - for line in io.lines(users_filename) do +local function trim(s) + return (string.gsub(s, "^%s*(.-)%s*$", "%1")) +end + +-- Return the stored password hash for a user, or nil. Reads the users file +-- fresh each call. A missing or unreadable file, and any unparsable line, are +-- skipped rather than fatal. +function account_hash(user) + if user == nil then + return nil + end + local wanted = user:lower() + local f = io.open(users_filename, "r") + if f == nil then + return nil + end + for line in f:lines() do local u, h = string.match(line, "(.-):(.+)") - if u:lower() == user:lower() then + if u ~= nil and trim(u):lower() == wanted then + f:close() return h end end + f:close() return nil end --- Looks up users for a given repo. -function lookup_users(repo) - local users = nil +-- Return the set of users allowed to access a repository, keyed by lowercased +-- username, or nil if the repository is not protected. A protected repository +-- whose groups resolve to no users returns an EMPTY table, which denies +-- everyone rather than falling through to public. +function repo_userset(repo) + if repo == nil then + return nil + end local groups = nil - local line, group, user - for line in io.lines(repos_filename) do - local r, g = string.match(line, "(.-):(.+)") - if r == repo then - groups = { } - for group in string.gmatch(g, "([^,]+)") do - groups[group:lower()] = true + local f = io.open(repos_filename, "r") + if f ~= nil then + for line in f:lines() do + local r, g = string.match(line, "(.-):(.+)") + if r ~= nil and trim(r) == repo then + groups = {} + for group in string.gmatch(g, "([^,]+)") do + groups[trim(group):lower()] = true + end + break end - break end + f:close() end if groups == nil then return nil end - for line in io.lines(groups_filename) do - local g, u = string.match(line, "(.-):(.+)") - if groups[g:lower()] then - if users == nil then - users = { } - end - for user in string.gmatch(u, "([^,]+)") do - users[user:lower()] = true + local users = {} + local gf = io.open(groups_filename, "r") + if gf ~= nil then + for line in gf:lines() do + local g, u = string.match(line, "(.-):(.+)") + if g ~= nil and groups[trim(g):lower()] then + for user in string.gmatch(u, "([^,]+)") do + users[trim(user):lower()] = true + end end end + gf:close() end return users end - --- Sets HTTP cookie headers based on post and sets up redirection. -function authenticate_post() - local hash = lookup_hash(post["username"]) - local redirect = validate_value("redirect", post["redirect"]) - - if redirect == nil then - not_found() - return 0 - end - - redirect_to(redirect) - - if hash == nil or hash ~= unistd.crypt(post["password"], hash) then - set_cookie("cgitauth", "") - else - -- One week expiration time - local username = secure_value("username", post["username"], os.time() + 604800) - set_cookie("cgitauth", username) - end - - html("\n") - return 0 -end - - --- Returns 1 if the cookie is valid and 0 if it is not. -function authenticate_cookie() - accepted_users = lookup_users(cgit["repo"]) - if accepted_users == nil then - -- We return as valid if the repo is not protected. - return 1 - end - - local username = validate_value("username", get_cookie(http["cookie"], "cgitauth")) - if username == nil or not accepted_users[username:lower()] then - return 0 - else - return 1 - end -end - --- Prints the html for the login form. -function body() - html("<h2>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 - - - --- --- --- 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. @@ -225,17 +224,23 @@ function url_encode(str) return str end +-- Parse an application/x-www-form-urlencoded body. A value may itself contain +-- '=', for example a base64 password, so the value runs to the next '&'. function parse_qs(qs) local tab = {} - for key, val in string.gmatch(qs, "([^&=]+)=([^&=]*)&?") do + for key, val in string.gmatch(qs or "", "([^&=]+)=([^&]*)") do tab[url_decode(key)] = url_decode(val) end return tab end +-- Return the value of the named cookie, or nil. The stored token was already +-- url-encoded by secure_value, so it is returned verbatim, which keeps the +-- write path (set_cookie) and the read path symmetric. Decoding it here would +-- break the signature check for any value carrying a percent escape. function get_cookie(cookies, name) - cookies = string.gsub(";" .. cookies .. ";", "%s*;%s*", ";") - return url_decode(string.match(cookies, ";" .. name .. "=(.-);")) + cookies = string.gsub(";" .. (cookies or "") .. ";", "%s*;%s*", ";") + return string.match(cookies, ";" .. name .. "=(.-);") end function tohex(b) @@ -254,7 +259,9 @@ end local secret = nil --- Loads a secret from a file, creates a secret, or returns one from memory. +-- Load the cookie-signing secret, creating it on first use. Failures raise, +-- which cgit turns into a request error, so a broken secret denies rather than +-- signs with nothing. function get_secret() if secret ~= nil then return secret @@ -265,27 +272,48 @@ function get_secret() local temporary_filename = secret_filename .. ".tmp." .. tohex(rand.bytes(16)) local temporary_file = io.open(temporary_filename, "w") if temporary_file == nil then - os.exit(177) + sysstat.umask(old_umask) + error("cgit auth: cannot create secret file " .. secret_filename) + end + local wrote = temporary_file:write(tohex(rand.bytes(32))) + local closed = temporary_file:close() + if not wrote or not closed then + os.remove(temporary_filename) + sysstat.umask(old_umask) + error("cgit auth: failed writing secret file " .. secret_filename) end - temporary_file:write(tohex(rand.bytes(32))) - temporary_file:close() - unistd.link(temporary_filename, secret_filename) -- Intentionally fails in the case that another process is doing the same. + unistd.link(temporary_filename, secret_filename) -- Intentionally fails if another worker won the race. unistd.unlink(temporary_filename) sysstat.umask(old_umask) secret_file = io.open(secret_filename, "r") end if secret_file == nil then - os.exit(177) + error("cgit auth: cannot read secret file " .. secret_filename) end - secret = secret_file:read() + secret = secret_file:read("*l") secret_file:close() - if secret:len() ~= 64 then - os.exit(177) + if secret == nil or secret:len() ~= 64 then + secret = nil + error("cgit auth: secret file " .. secret_filename .. " is malformed, expected 64 hex characters") end return secret end --- Returns value of cookie if cookie is valid. Otherwise returns nil. +-- A redirect target is unsafe if a browser would read it as another origin. +-- The only such form cgit can be tricked into signing is a scheme-relative +-- "//host" or "/\host". Everything else stays on this host. +function is_safe_redirect(url) + if type(url) ~= "string" then + return false + end + local head = url:sub(1, 2) + if head == "//" or head == "/\\" then + return false + end + return true +end + +-- Return the value carried by a signed cookie, or nil if it does not verify. function validate_value(expected_field, cookie) local i = 0 local value = "" @@ -304,10 +332,13 @@ function validate_value(expected_field, cookie) elseif i == 1 then value = component elseif i == 2 then - expiration = tonumber(component) - if expiration == nil then - expiration = -1 + -- The expiration must be a plain integer. Rejecting other forms + -- keeps the signed bytes canonical, since tonumber and tostring of + -- "1e9" or "100.0" differ across Lua versions. + if not string.match(component, "^%d+$") then + return nil end + expiration = tonumber(component) elseif i == 3 then salt = component elseif i == 4 then @@ -327,7 +358,8 @@ function validate_value(expected_field, cookie) return nil end - if expiration == -1 or (expiration ~= 0 and expiration <= os.time()) then + -- An expiration of 0 never expires and is used for the redirect token. + if expiration ~= 0 and expiration <= os.time() then return nil end @@ -336,8 +368,8 @@ function validate_value(expected_field, cookie) end local decoded = url_decode(value) - -- Reject values carrying control characters so a signed cookie or - -- redirect target cannot smuggle CR or LF into a response header. + -- Reject values carrying control characters so a signed value cannot + -- smuggle CR or LF into a response header. if decoded:find("%c") then return nil end @@ -349,11 +381,10 @@ function secure_value(field, value, expiration) return "" end - local authstr = "" local salt = tohex(rand.bytes(16)) value = url_encode(value) field = url_encode(field) - authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt + local authstr = field .. "|" .. value .. "|" .. tostring(expiration) .. "|" .. salt authstr = authstr .. "|" .. tohex(hmac.new(get_secret(), "sha256"):final(authstr)) return authstr end @@ -363,27 +394,31 @@ function strip_ctl(s) return (string.gsub(s or "", "%c", "")) end --- Compare two strings without stopping at the first mismatch, so the time --- taken does not reveal how many leading bytes already matched. +-- Compare two strings in time that does not depend on how many leading bytes +-- match, so a mismatch position is not revealed by timing. function constant_equals(a, b) - if a == nil or b == nil or #a ~= #b then + if type(a) ~= "string" or type(b) ~= "string" or #a ~= #b then return false end local diff = 0 for i = 1, #a do - if a:byte(i) ~= b:byte(i) then - diff = diff + 1 - end + local d = a:byte(i) - b:byte(i) + diff = diff + d * d end return diff == 0 end function set_cookie(cookie, value) - html("Set-Cookie: " .. cookie .. "=" .. strip_ctl(value) .. "; HttpOnly; SameSite=Lax") - if http["https"] == "yes" or http["https"] == "on" or http["https"] == "1" then - html("; secure") + local attrs = "; HttpOnly; SameSite=Lax; Path=" .. cookie_path + if not cookie_insecure then + attrs = attrs .. "; Secure" end - html("\n") + if value == "" then + attrs = attrs .. "; Max-Age=0" + elseif session_seconds > 0 then + attrs = attrs .. "; Max-Age=" .. tostring(session_seconds) + end + html("Set-Cookie: " .. cookie .. "=" .. strip_ctl(value) .. attrs .. "\n") end function redirect_to(url) @@ -396,3 +431,126 @@ function not_found() html("Status: 404 Not Found\n") html("Cache-Control: no-cache, no-store\n\n") end + +-- +-- +-- Authentication actions. Identical to auth-inline.lua from here down. +-- +-- + +-- Sets HTTP cookie headers based on post and sets up redirection. +function authenticate_post() + local redirect = validate_value("redirect", post["redirect"]) + + if redirect == nil or not is_safe_redirect(redirect) then + not_found() + return 0 + end + + redirect_to(redirect) + + local username = post["username"] + local password = post["password"] + local ok = false + if username ~= nil and password ~= nil then + local hash = account_hash(username) + if hash == nil then + -- Spend the work anyway, see dummy_hash. + unistd.crypt(password, dummy_hash) + elseif constant_equals(hash, unistd.crypt(password, hash)) then + ok = true + end + end + + if ok then + set_cookie(cookie_name, secure_value("username", username, os.time() + session_seconds)) + else + set_cookie(cookie_name, "") + end + + html("\n") + return 0 +end + +-- Returns 1 if the cookie is valid and 0 if it is not. +function authenticate_cookie() + local accepted_users = repo_userset(cgit["repo"]) + if accepted_users == nil then + -- The repository is not protected. + return 1 + end + + local username = validate_value("username", get_cookie(http["cookie"], cookie_name)) + if username == nil or not accepted_users[username:lower()] then + return 0 + end + return 1 +end + +-- Prints the html for the login form. +function body() + local target = cgit["url"] + if not is_safe_redirect(target) then + target = cgit["login"] + end + + html("<h2>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", target, 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 + +-- +-- +-- Wrapper around the filter API, exposing the http, cgit and post tables to +-- the functions above. +-- +-- + +local actions = {} +actions["authenticate-post"] = authenticate_post +actions["authenticate-cookie"] = authenticate_cookie +actions["body"] = body + +function filter_open(...) + action = actions[select(1, ...)] + + post = {} + + 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() + if action == nil then + -- Unknown action, deny rather than raise. + return 0 + end + return action() +end + +function filter_write(str) + post = parse_qs(str) +end |