From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5B97F2E413 for ; Sun, 24 May 2026 01:02:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779584538; cv=none; b=qNmejJL4vtdLwfr+ov0hq0BfR1Vmbme6HU+PqXObzBvs4VbUHkV2DAOUuOIWLQIhc1ssN/jpekf3yymTVT8y5ESU5nxyVd8lIA9sWyNl/zx5ur3G8jHRXjjnQd67uhdZmgh/r8nezPt1KLlF1AQDXoxu2MLWLHjz1sD9ZYxzDf8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779584538; c=relaxed/simple; bh=FDja62qw8bkI4CPImoD/etC1XjkiEcyv8eEKKEYaMg8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Elg2eSZ76k7frIEbdojpqu4Y+ZDVypsUZQ/Ur/I4t71XEXHmP63IJCYeMGsK7rRcOAlZy8jGxQFnspKjx6KUK6TpYjrxTWOCM+41JnDFTx1swTISVNtXYYEmoZIrgOFGeFYaA/qmNhwvaOZXS7Wp9HMq7YNxeXBV4YfCPzE5REo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ANi4klcc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ANi4klcc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DF1A1F00A3C; Sun, 24 May 2026 01:02:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779584537; bh=SXz6vGnO0sovCOMh8rPvoswISDScH1ca7oeC2gQdrPo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ANi4klcc8BKUUGIGZ3tM08GSANOHsMpKeZdZY+nAk358B285zZ7JGgk99VhmGAX60 jxPcrceWGGT1aPplycccGTKcRvkkQqngTL5fVCQuX5sQ2XAdB4G/wBYbmQ8TJJ9uwZ dWs0onUdFL7XorFeTmvOpzQEUb59QK9ijOZUKY32vsIT8P4Gs2dDuKSUXStlTzBcv1 3VpERxqeASGI9HLOettzZutkzPk4bdVgEyHUSSHn47ac2rhhWiQc5AzbFPJ+rxJ732 qRBwpj/ZY7Dz4EQrUm6HO5BYqmDhcmg9iTgDBx5JlMnLEIUJmnlFJoxgmi4u3c6obm +yyBsVfAgM3Ag== From: Chuck Lever To: Trond Myklebust , Anna Schumaker , NeilBrown , Jeff Layton , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: , Chris Mason Subject: [PATCH 1/4] SUNRPC: svcauth_gss: enforce krb5 token minimum length Date: Sat, 23 May 2026 21:02:10 -0400 Message-ID: <20260524010213.557424-2-cel@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260524010213.557424-1-cel@kernel.org> References: <20260524010213.557424-1-cel@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chris Mason svcauth_gss_unwrap_priv() validates only an upper bound on the wire-supplied opaque length before handing the buffer to gss_unwrap(): if (len > xdr_stream_remaining(xdr)) goto unwrap_failed; offset = xdr_stream_pos(xdr); ... maj_stat = gss_unwrap(ctx, offset, offset + len, buf); The wire value `len` flows unchanged as the upper bound into the krb5 unwrap path, so a len in [0, 16] passes this check and is handed to gss_unwrap(). For a krb5 v2 context that lands in gss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token header fields at ptr+4 and ptr+6 and then calls rotate_left() before any integrity check. With a sub-header length the header reads run past the token, and _rotate_left()'s `shift %= buf->len` path can divide by zero when buf->len has been driven to zero by the truncated token. A header-only token (len == 16) is equally invalid: with a non-zero RRC field and the opaque blob ending at the XDR buffer boundary, rotate_left() builds a zero-length subbuffer, reaching the same division. Reject the token at the server entry point before it reaches the krb5 unwrap core. A valid sealed RFC 4121 token must contain the 16-byte header plus at least some encrypted payload. Fix by adding a minimum-length check immediately after the existing upper-bound check: if (len <= GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed; Fixes: 7c9fdcfb1b64 ("[PATCH] knfsd: svcrpc: gss: server-side implementation of rpcsec_gss privacy") Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Signed-off-by: Chuck Lever --- net/sunrpc/auth_gss/svcauth_gss.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c index d14209031e18..8e8aceb31270 100644 --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -949,6 +949,8 @@ svcauth_gss_unwrap_priv(struct svc_rqst *rqstp, u32 seq, struct gss_ctx *ctx) } if (len > xdr_stream_remaining(xdr)) goto unwrap_failed; + if (len <= GSS_KRB5_TOK_HDR_LEN) + goto unwrap_failed; offset = xdr_stream_pos(xdr); saved_len = buf->len; -- 2.54.0