Updated value in secret column does not get encrypted

[Tim Reibe]

Hi everyone,

following my setup in #73, I have a secret value stored in secret_column, which is encrypted at insert.
Now, when updating the value, I expect it to be encrypted again, but it won't. Edit: It is stored as clear text.

Is this behavior expected, or is this, again, an issue I have with supabase?

Kind regards
Tim

edit: I added the database setup scripts in my comment below

[Tim Reibe]

As a workaround, I created an update trigger, which sets a new key_id and nonce and encryptes the secret value again with both.

• Setup Database
  In this case, I have a column named owner which references to my (supabase) users table.

CREATE TABLE table_name1 (
   id uuid PRIMARY KEY NOT NULL DEFAULT uuid_generate_v4(),
   owner uuid NOT NULL REFERENCES auth.users (id),
   key_id uuid NOT NULL REFERENCES pgsodium.key(id) DEFAULT (pgsodium.create_key()).id,
   nonce bytea NOT NULL DEFAULT pgsodium.crypto_aead_det_noncegen(),
   secret_column text NOT NULL DEFAULT 'undefined'::text
);

SECURITY LABEL FOR pgsodium
  ON COLUMN table_name1.secret_column
  IS 'ENCRYPT WITH KEY COLUMN key_id NONCE nonce ASSOCIATED owner';

CREATE VIEW decrypted_table_name1 AS
  SELECT id,
         convert_from(pgsodium.crypto_aead_det_decrypt(
           pg_catalog.decode(secret_column, 'base64'),
           pg_catalog.convert_to(owner::text, 'utf8'),
           key_id::uuid,
           nonce
         ), 'utf8') AS secret_column
         FROM table_name1;

• Create Trigger

create or replace function set_table_name1_pgsodium_values()
    returns trigger
as
$$
begin

    new.key_id := (pgsodium.create_key()).id;
    new.nonce :=  pgsodium.crypto_aead_det_noncegen();

    new.secret_column := pg_catalog.encode(
        pgsodium.crypto_aead_det_encrypt(
            pg_catalog.convert_to(new.secret_column, 'utf8'),
            pg_catalog.convert_to(old.owner::text, 'utf8'),
            new.key_id,
            new.nonce
        ),
    'base64');
    return new;
end ;
$$
    language plpgsql;

create trigger trg_set_table_name1_pgsodium_values
    before update
    on table_name1
    for each row
execute procedure set_table_name1_pgsodium_values();

[Jehan-Guillaume (ioguix) de Rorthais]

Now, when updating the value, I expect it to be encrypted again, but it won't.

What do you mean "it won't"? Does the updated data is written in clear text/bytea?

Here is a similar Q+A if it could help: #61 (comment)

[Tim Reibe]

Hi @ioguix, the updated data is written in clear text and not encrypted.

Thanks for the Q&A, so to trigger the encryption correctly, I have to update the value via the decrypted view, correct? Is there any advantage/disadvantage over having a trigger that encrypts the value on an update call?

Another thing is: I'd like to update the key_id and nonce on every change of the secret column, can I somehow integrate this in an alternative way than using an update trigger?

[Jehan-Guillaume (ioguix) de Rorthais]

Hi,

I have to update the value via the decrypted view, correct?

Not necessarily if you don't build the new value with the old one.

I have no idea why your trigger does not fire:

76=# select secret_column, decrypted_secret_column from decrypted_table_name1 ;
                  secret_column                   | decrypted_secret_column 
--------------------------------------------------+-------------------------
 ke6mSPa146SZZFdMa+8bJzN8bHjg/sC45oGEUk3UzNRsX21/ | chut
(1 row)

76=# update table_name1 set secret_column = 'chuuuuuut';
UPDATE 1
76=# select secret_column, decrypted_secret_column from decrypted_table_name1 ;
                      secret_column                       | decrypted_secret_column 
----------------------------------------------------------+-------------------------
 9ubE1JtNuXWxtslVDdzv68vFKUaiu7bponbkMaIcWmRujdv+mSZjD5g= | chuuuuuut
(1 row)

I don't understand either why you create the decrypted_table_name1 view yourself as pgsodium is supposed to build it for you.

[Tim Reibe]

That the decrypted view is not generated dynamically seems to be related with my supabase setup again. Some others had the same issue: supabase/supabase#11209. This might be an issue with the supabase version my project is built with. On a new project, pgsodium just works flawlessly - also the value update! Now I have to figure out how I can upgrade my project.

Thank you @ioguix