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Diffstat (limited to 'guides/source/security.md')
| -rw-r--r-- | guides/source/security.md | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/guides/source/security.md b/guides/source/security.md index 1fcb2fc91f..f69a0c72b0 100644 --- a/guides/source/security.md +++ b/guides/source/security.md @@ -95,16 +95,23 @@ Rails 2 introduced a new default session storage, CookieStore. CookieStore saves * The client can see everything you store in a session, because it is stored in clear-text (actually Base64-encoded, so not encrypted). So, of course, _you don't want to store any secrets here_. To prevent session hash tampering, a digest is calculated from the session with a server-side secret (`secrets.secret_token`) and inserted into the end of the cookie. -However, since Rails 4, the default store is EncryptedCookieStore. With -EncryptedCookieStore the session is encrypted before being stored in a cookie. -This prevents the user from accessing and tampering the content of the cookie. -Thus the session becomes a more secure place to store data. The encryption is -done using a server-side secret key `secrets.secret_key_base` stored in -`config/secrets.yml`. +In Rails 4, encrypted cookies through AES in CBC mode with HMAC using SHA1 for +verification was introduced. This prevents the user from accessing and tampering +the content of the cookie. Thus the session becomes a more secure place to store +data. The encryption is performed using a server-side `secrets.secret_key_base`. +Two salts are used when deriving keys for encryption and verification. These +salts are set via the `config.action_dispatch.encrypted_cookie_salt` and +`config.action_dispatch.encrypted_signed_cookie_salt` configuration values. -That means the security of this storage depends on this secret (and on the digest algorithm, which defaults to SHA1, for compatibility). So _don't use a trivial secret, i.e. a word from a dictionary, or one which is shorter than 30 characters, use `rails secret` instead_. +Rails 5.2 uses AES-GCM for the encryption which couples authentication +and encryption in one faster step and produces shorter ciphertexts. -`secrets.secret_key_base` is used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications get `secrets.secret_key_base` initialized to a random key present in `config/secrets.yml`, e.g.: +Encrypted cookies are automatically upgraded if the +`config.action_dispatch.use_authenticated_cookie_encryption` is enabled. + +_Do not use a trivial secret, i.e. a word from a dictionary, or one which is shorter than 30 characters! Instead use `rails secret` to generate secret keys!_ + +Applications get `secrets.secret_key_base` initialized to a random key present in `config/secrets.yml`, e.g.: development: secret_key_base: a75d... @@ -356,7 +363,7 @@ send_file('/var/www/uploads/' + params[:filename]) Simply pass a file name like "../../../etc/passwd" to download the server's login information. A simple solution against this, is to _check that the requested file is in the expected directory_: ```ruby -basename = File.expand_path(File.join(File.dirname(__FILE__), '../../files')) +basename = File.expand_path('../../files', __dir__) filename = File.expand_path(File.join(basename, @file.public_filename)) raise if basename != File.expand_path(File.join(File.dirname(filename), '../../../')) |