Re: [PATCH 2/2] scsi: target: fix auth when CHAP_N carries a hex/b64 prefix

On Tue, Jun 2, 2026 at 5:04 AM David Disseldorp <[email protected]> wrote:
>
> Attempting to authenticate using a CHAP username with a '0x' or '0b'
> prefix currently fails. This is due to extract_param()'s behaviour of
> stripping these prefixes, and the subsequent (type == HEX) error-path.
> I believe this behaviour is contrary to the RFC 3720 specification,
> which states:
>
>   5.1.  Text Format
>   ...
>   text-value: A string of zero or more characters that consist of
>   letters, digits, dot, minus, plus, commercial at, underscore,
>   slash, left bracket, right bracket, or colon.
>
>   11.1.4.  Challenge Handshake Authentication Protocol (CHAP)
>   ...
>     CHAP_A=<A> CHAP_I=<I> CHAP_C=<C>
>
>    Where A is one of A1,A2... that were proposed by the initiator.
>
>    In the third step, the initiator MUST continue with:
>
>       CHAP_N=<N> CHAP_R=<R>
>    ...
>    Where N, (A,A1,A2), I, C, and R are (correspondingly) the Name,
>    Algorithm, Identifier, Challenge, and Response as defined in
>    [RFC1994], N is a text string, A,A1,A2, and I are numbers, and C and
>    R are large-binary-values ...
>
> "N is a text string" implies that any hex or base64 encoding prefix
> should not be interpreted or stripped. Fix this by using the new
> extract_param_str() helper function to obtain the CHAP_N value as-is.
>
> Reported-by: Sashiko (gemini/gemini-3.1-pro-preview)
> Link: https://sashiko.dev/#/patchset/20260521151121.808477-1-hossu.alexandru%40gmail.com
> Signed-off-by: David Disseldorp <[email protected]>
> ---
>  drivers/target/iscsi/iscsi_target_auth.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/target/iscsi/iscsi_target_auth.c b/drivers/target/iscsi/iscsi_target_auth.c
> index a3ad2d244dbee..6f21075e58416 100644
> --- a/drivers/target/iscsi/iscsi_target_auth.c
> +++ b/drivers/target/iscsi/iscsi_target_auth.c
> @@ -303,12 +303,8 @@ static int chap_server_compute_hash(
>         /*
>          * Extract CHAP_N.
>          */
> -       if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
> -                               &type) < 0) {
> -               pr_err("Could not find CHAP_N.\n");
> -               goto out;
> -       }
> -       if (type == HEX) {
> +       ret = extract_param_str(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n);
> +       if (ret < 0) {
>                 pr_err("Could not find CHAP_N.\n");
>                 goto out;
>         }
> --
> 2.51.0
>
>

Reviewed-by: Lee Duncan <[email protected]>