Switch Access / Refresh tokens / Auth Code from bcrypt ( and plain ) to hmac. BCrypt is for low entropy passwords and prevents dictionary attacks - HMAC is suitable for 256-bit random data.

app/models/concerns/token_prefixable.rb

@@ -1,53 +0,0 @@
-module TokenPrefixable
-  extend ActiveSupport::Concern
-
-  class_methods do
-    # Compute HMAC prefix from plaintext token
-    # Returns first 8 chars of Base64url-encoded HMAC
-    # Does NOT reveal anything about the token
-    def compute_token_prefix(plaintext_token)
-      return nil if plaintext_token.blank?
-
-      hmac = OpenSSL::HMAC.digest('SHA256', TokenHmac::KEY, plaintext_token)
-      Base64.urlsafe_encode64(hmac)[0..7]
-    end
-
-    # Find token using HMAC prefix lookup (fast, indexed)
-    def find_by_token(plaintext_token)
-      return nil if plaintext_token.blank?
-
-      prefix = compute_token_prefix(plaintext_token)
-
-      # Fast indexed lookup by HMAC prefix
-      where(token_prefix: prefix).find_each do |token|
-        return token if token.token_matches?(plaintext_token)
-      end
-
-      nil
-    end
-  end
-
-  # Check if a plaintext token matches the hashed token
-  def token_matches?(plaintext_token)
-    return false if plaintext_token.blank? || token_digest.blank?
-
-    BCrypt::Password.new(token_digest) == plaintext_token
-  rescue BCrypt::Errors::InvalidHash
-    false
-  end
-
-  # Generate new token with HMAC prefix
-  # Sets both virtual attribute (for returning to client) and digest (for storage)
-  def generate_token_with_prefix
-    plaintext = SecureRandom.urlsafe_base64(48)
-    self.token_prefix = self.class.compute_token_prefix(plaintext)
-    self.token_digest = BCrypt::Password.create(plaintext)
-
-    # Set the virtual attribute - different models use different names
-    if respond_to?(:plaintext_token=)
-      self.plaintext_token = plaintext  # OidcAccessToken
-    elsif respond_to?(:token=)
-      self.token = plaintext  # OidcRefreshToken
-    end
-  end
-end

app/models/oidc_access_token.rb

@@ -1,15 +1,12 @@
 class OidcAccessToken < ApplicationRecord
-  include TokenPrefixable
-
   belongs_to :application
   belongs_to :user
   has_many :oidc_refresh_tokens, dependent: :destroy
 
-  before_validation :generate_token_with_prefix, on: :create
+  before_validation :generate_token, on: :create
   before_validation :set_expiry, on: :create
 
-  validates :token_digest, presence: true
-  validates :token_prefix, presence: true
+  validates :token_hmac, presence: true, uniqueness: true
 
   scope :valid, -> { where("expires_at > ?", Time.current).where(revoked_at: nil) }
   scope :expired, -> { where("expires_at <= ?", Time.current) }
@@ -18,6 +15,19 @@ class OidcAccessToken < ApplicationRecord
 
   attr_accessor :plaintext_token  # Store plaintext temporarily for returning to client
 
+  # Find access token by plaintext token using HMAC verification
+  def self.find_by_token(plaintext_token)
+    return nil if plaintext_token.blank?
+
+    token_hmac = compute_token_hmac(plaintext_token)
+    find_by(token_hmac: token_hmac)
+  end
+
+  # Compute HMAC for token lookup
+  def self.compute_token_hmac(plaintext_token)
+    OpenSSL::HMAC.hexdigest('SHA256', TokenHmac::KEY, plaintext_token)
+  end
+
   def expired?
     expires_at <= Time.current
   end
@@ -36,11 +46,15 @@ class OidcAccessToken < ApplicationRecord
     oidc_refresh_tokens.each(&:revoke!)
   end
 
-  # find_by_token, token_matches?, and generate_token_with_prefix
-  # are now provided by TokenPrefixable concern
-
   private
 
+  def generate_token
+    # Generate random plaintext token
+    self.plaintext_token ||= SecureRandom.urlsafe_base64(48)
+    # Store HMAC in database (not plaintext)
+    self.token_hmac ||= self.class.compute_token_hmac(plaintext_token)
+  end
+
   def set_expiry
     self.expires_at ||= application.access_token_expiry
   end

app/models/oidc_authorization_code.rb

@@ -7,7 +7,7 @@ class OidcAuthorizationCode < ApplicationRecord
   before_validation :generate_code, on: :create
   before_validation :set_expiry, on: :create
 
-  validates :code, presence: true, uniqueness: true
+  validates :code_hmac, presence: true, uniqueness: true
   validates :redirect_uri, presence: true
   validates :code_challenge_method, inclusion: { in: %w[plain S256], allow_nil: true }
   validate :validate_code_challenge_format, if: -> { code_challenge.present? }
@@ -20,7 +20,7 @@ class OidcAuthorizationCode < ApplicationRecord
     return nil if plaintext_code.blank?
 
     code_hmac = compute_code_hmac(plaintext_code)
-    find_by(code: code_hmac)
+    find_by(code_hmac: code_hmac)
   end
 
   # Compute HMAC for code lookup
@@ -50,7 +50,7 @@ class OidcAuthorizationCode < ApplicationRecord
     # Generate random plaintext code
     self.plaintext_code ||= SecureRandom.urlsafe_base64(32)
     # Store HMAC in database (not plaintext)
-    self.code ||= self.class.compute_code_hmac(plaintext_code)
+    self.code_hmac ||= self.class.compute_code_hmac(plaintext_code)
   end
 
   def set_expiry

app/models/oidc_refresh_token.rb

@@ -1,16 +1,13 @@
 class OidcRefreshToken < ApplicationRecord
-  include TokenPrefixable
-
   belongs_to :application
   belongs_to :user
   belongs_to :oidc_access_token
 
-  before_validation :generate_token_with_prefix, on: :create
+  before_validation :generate_token, on: :create
   before_validation :set_expiry, on: :create
   before_validation :set_token_family_id, on: :create
 
-  validates :token_digest, presence: true, uniqueness: true
-  validates :token_prefix, presence: true
+  validates :token_hmac, presence: true, uniqueness: true
 
   scope :valid, -> { where("expires_at > ?", Time.current).where(revoked_at: nil) }
   scope :expired, -> { where("expires_at <= ?", Time.current) }
@@ -22,6 +19,19 @@ class OidcRefreshToken < ApplicationRecord
 
   attr_accessor :token  # Store plaintext token temporarily for returning to client
 
+  # Find refresh token by plaintext token using HMAC verification
+  def self.find_by_token(plaintext_token)
+    return nil if plaintext_token.blank?
+
+    token_hmac = compute_token_hmac(plaintext_token)
+    find_by(token_hmac: token_hmac)
+  end
+
+  # Compute HMAC for token lookup
+  def self.compute_token_hmac(plaintext_token)
+    OpenSSL::HMAC.hexdigest('SHA256', TokenHmac::KEY, plaintext_token)
+  end
+
   def expired?
     expires_at <= Time.current
   end
@@ -45,11 +55,15 @@ class OidcRefreshToken < ApplicationRecord
     OidcRefreshToken.in_family(token_family_id).update_all(revoked_at: Time.current)
   end
 
-  # find_by_token, token_matches?, and generate_token_with_prefix
-  # are now provided by TokenPrefixable concern
-
   private
 
+  def generate_token
+    # Generate random plaintext token
+    self.token ||= SecureRandom.urlsafe_base64(48)
+    # Store HMAC in database (not plaintext)
+    self.token_hmac ||= self.class.compute_token_hmac(token)
+  end
+
   def set_expiry
     # Use application's configured refresh token TTL
     self.expires_at ||= application.refresh_token_expiry