Re: [pbs-devel] [PATCH proxmox-backup 1/2] fix #3853: api: add force option to tape key change-passphrase

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

On 07.02.22 13:48, Stefan Sterz wrote:
> When force is used, the current passphrase is not required. Instead
> it will be read from the file pointed to by TAPE_KEYS_FILENAME and
> the old key configuration will be overwritten using the new
> passphrase.
> 

looks quite ok, some nits/suggestions in line.

> Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>
> ---
>  src/api2/config/tape_encryption_keys.rs | 36 ++++++++++++++++++++++---
>  1 file changed, 33 insertions(+), 3 deletions(-)
> 
> diff --git a/src/api2/config/tape_encryption_keys.rs b/src/api2/config/tape_encryption_keys.rs
> index 1ad99377..b31f741d 100644
> --- a/src/api2/config/tape_encryption_keys.rs
> +++ b/src/api2/config/tape_encryption_keys.rs
> @@ -70,6 +70,7 @@ pub fn list_keys(
>              password: {
>                  description: "The current password.",
>                  min_length: 5,
> +                optional: true,
>              },
>              "new-password": {
>                  description: "The new password.",
> @@ -78,6 +79,12 @@ pub fn list_keys(
>              hint: {
>                  schema: PASSWORD_HINT_SCHEMA,
>              },
> +            force: {
> +                optional: true,
> +                type: bool,
> +                description: "Don't ask for the old passphrase and overwrite it. Root only.",

Maybe we can better hint that we reset the password by restoring/re-using the
original key, which is naturally only possible if the key available, e.g.:

"Reset password for tape key-copy using original, root-only accessible key"

> +                default: false,
> +            },
>              digest: {
>                  optional: true,
>                  schema: PROXMOX_CONFIG_DIGEST_SCHEMA,
> @@ -91,9 +98,10 @@ pub fn list_keys(
>  /// Change the encryption key's password (and password hint).
>  pub fn change_passphrase(
>      kdf: Option<Kdf>,
> -    password: String,
> +    password: Option<String>,
>      new_password: String,
>      hint: String,
> +    force: bool,
>      fingerprint: Fingerprint,
>      digest: Option<String>,
>      _rpcenv: &mut dyn RpcEnvironment
> @@ -116,10 +124,32 @@ pub fn change_passphrase(
>  
>      let key_config = match config_map.get(&fingerprint) {
>          Some(key_config) => key_config,
> -        None => bail!("tape encryption key '{}' does not exist.", fingerprint),
> +        None => bail!("tape encryption key configuration '{}' does not exist.", fingerprint),
> +    };
> +
> +    // sanity checks for "password xor --force"
> +    if force && password.is_some() {
> +        bail!("password is not allowed when using force")
> +    }
> +
> +    if !force && password.is_none() {
> +        bail!("missing parameter: password")
> +    }

Above two if's could be written slightly shorter while IMO even improving readability

match (force, password) {
    (true, Some(_)) => bail!("password is not allowed when using force"),
    (false, None) => bail!("missing parameter: password"),
    _ => (), // OK
}

We probably could even extend this over the "decrypt old key or force loading old key from plaintext
file" part below, so that the whole things looks something like (untested):


let (key, created, fingerprint) = match (force, password) {
    (true, Some(_)) => bail!("password is not allowed when using force"),
    (false, None) => bail!("missing parameter: password"),
    (true, Some(pass)) => key_config.decrypt(&|| Ok(pass.as_bytes().to_vec()))?,
    (false, None) => {
        let key = load_keys()?.map(|keys, _| key.get(&fingerprint)).unwrap_or_else(|| bail!("..."));
        (key, key_config.created, fingerprint)
    }
}

but not to hard feeling there, may get seen as a little bit too condensed...

> +
> +    // decrypt old key or force loading old key from plaintext file
> +    let (key, created, fingerprint) = if let Some(pass) = password {
> +        key_config.decrypt(&|| Ok(pass.as_bytes().to_vec()))?
> +    } else {
> +        let (key_map, _) = load_keys()?;
> +
> +        let key = match key_map.get(&fingerprint) {
> +            Some(k) => k.key,
> +            None => bail!("tape encryption key '{}' does not exist.", fingerprint)

error message could be slightly improved with context:
 "failed to reset key password, original tape enc..."

> +        };
> +
> +        (key, key_config.created, fingerprint)
>      };
>  
> -    let (key, created, fingerprint) = key_config.decrypt(&|| Ok(password.as_bytes().to_vec()))?;
>      let mut new_key_config = KeyConfig::with_key(&key, new_password.as_bytes(), kdf)?;
>      new_key_config.created = created; // keep original value
>      new_key_config.hint = Some(hint);