> On Mar 26, 2020, at 10:24 AM, Olga Kornievskaia <olga.kornievskaia@xxxxxxxxx> wrote:
>
> Ever since commit 2c94b8eca1a2 ("SUNRPC: Use au_rslack when computing
> reply buffer size"). It changed how "req->rq_rcvsize" is calculated. It
> used to use au_cslack value which was nice and large and changed it to
> au_rslack value which turns out to be too small.
>
> Since 5.1, v3 mount with sec=krb5p fails against an Ontap server
> because client's receive buffer it too small.
>
> For gss krb5p, we need to account for the mic token in the verifier,
> and the wrap token in the wrap token.
>
> RFC 4121 defines:
> mic token
> Octet no Name Description
> --------------------------------------------------------------
> 0..1 TOK_ID Identification field. Tokens emitted by
> GSS_GetMIC() contain the hex value 04 04
> expressed in big-endian order in this
> field.
> 2 Flags Attributes field, as described in section
> 4.2.2.
> 3..7 Filler Contains five octets of hex value FF.
> 8..15 SND_SEQ Sequence number field in clear text,
> expressed in big-endian order.
> 16..last SGN_CKSUM Checksum of the "to-be-signed" data and
> octet 0..15, as described in section 4.2.4.
>
> that's 16bytes (GSS_KRB5_TOK_HDR_LEN) + chksum
>
> wrap token
> Octet no Name Description
> --------------------------------------------------------------
> 0..1 TOK_ID Identification field. Tokens emitted by
> GSS_Wrap() contain the hex value 05 04
> expressed in big-endian order in this
> field.
> 2 Flags Attributes field, as described in section
> 4.2.2.
> 3 Filler Contains the hex value FF.
> 4..5 EC Contains the "extra count" field, in big-
> endian order as described in section 4.2.3.
> 6..7 RRC Contains the "right rotation count" in big-
> endian order, as described in section
> 4.2.5.
> 8..15 SND_SEQ Sequence number field in clear text,
> expressed in big-endian order.
> 16..last Data Encrypted data for Wrap tokens with
> confidentiality, or plaintext data followed
> by the checksum for Wrap tokens without
> confidentiality, as described in section
> 4.2.4.
>
> Also 16bytes of header (GSS_KRB5_TOK_HDR_LEN), encrypted data, and cksum
> (other things like padding)
>
> RFC 3961 defines known cksum sizes:
> Checksum type sumtype checksum section or
> value size reference
> ---------------------------------------------------------------------
> CRC32 1 4 6.1.3
> rsa-md4 2 16 6.1.2
> rsa-md4-des 3 24 6.2.5
> des-mac 4 16 6.2.7
> des-mac-k 5 8 6.2.8
> rsa-md4-des-k 6 16 6.2.6
> rsa-md5 7 16 6.1.1
> rsa-md5-des 8 24 6.2.4
> rsa-md5-des3 9 24 ??
> sha1 (unkeyed) 10 20 ??
> hmac-sha1-des3-kd 12 20 6.3
> hmac-sha1-des3 13 20 ??
> sha1 (unkeyed) 14 20 ??
> hmac-sha1-96-aes128 15 20 [KRB5-AES]
> hmac-sha1-96-aes256 16 20 [KRB5-AES]
> [reserved] 0x8003 ? [GSS-KRB5]
>
> Linux kernel now mainly supports type 15,16 so max cksum size is 20bytes.
> (GSS_KRB5_MAX_CKSUM_LEN)
>
> Re-use already existing define of GSS_KRB5_MAX_SLACK_NEEDED that's used
> for encoding the gss_wrap tokens (same tokens are used in reply).
>
> Fixes: 2c94b8eca1a2 ("SUNRPC: Use au_rslack when computing reply buffer size")
> Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> net/sunrpc/auth_gss/auth_gss.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> index 24ca861..d6cd2a5 100644
> --- a/net/sunrpc/auth_gss/auth_gss.c
> +++ b/net/sunrpc/auth_gss/auth_gss.c
> @@ -20,6 +20,7 @@
> #include <linux/sunrpc/clnt.h>
> #include <linux/sunrpc/auth.h>
> #include <linux/sunrpc/auth_gss.h>
> +#include <linux/sunrpc/gss_krb5.h>
> #include <linux/sunrpc/svcauth_gss.h>
> #include <linux/sunrpc/gss_err.h>
> #include <linux/workqueue.h>
> @@ -1050,7 +1051,7 @@ static void gss_pipe_free(struct gss_pipe *p)
> goto err_put_mech;
> auth = &gss_auth->rpc_auth;
> auth->au_cslack = GSS_CRED_SLACK >> 2;
> - auth->au_rslack = GSS_VERF_SLACK >> 2;
> + auth->au_rslack = GSS_KRB5_MAX_SLACK_NEEDED >> 2;
> auth->au_verfsize = GSS_VERF_SLACK >> 2;
> auth->au_ralign = GSS_VERF_SLACK >> 2;
> auth->au_flags = 0;
> --
> 1.8.3.1
>
--
Chuck Lever
