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 497524A0157 for ; Tue, 8 Sep 2026 17:55:50 +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=1788890151; cv=none; b=brwqoDemNLyMoDqDQHVFn7bnhrVhX1pSYXl51mQ77WH33VCBQbXv4R9QaYL/zqnd065upZ0z5e0dAPIRbojFbl+roidY48vfTe1ZbXe9or0C/Vi9k6ivF7c7dfIHtUlvlGSFdDYFJY1HEhfvNlkdka8QNO/Sz0dcRsODuxcjFcE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788890151; c=relaxed/simple; bh=HGfwBkxP4n+2PLVf5k4QgXmPyCHAbXQX5AupK1DU0a4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Xkc1YRz40N5QjXe6rQ4GCYKzy487D3KCQcOHozDuK0Z+WNfhN7/YhEM7xYVcTprKXg+aH/hoPr6b5tqze4wFL20J2ziisvZHXZFZvhOtUEsxno7RtT3aJ0CWswHn05GO7cQD+88/mp0cyp8vOFUfnfw7U4s6FhenK9Uqqqiq2zk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Jo+ND/nm; 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="Jo+ND/nm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A3EC1F00A3E; Tue, 8 Sep 2026 17:55:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788890150; bh=hGcR4GswoFaVKnQRUoWVg3mtuMzrAi7O7z32u1gmVGA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Jo+ND/nmIPR6msdAKn3f/oOEjQFWuKHrTFfI2ADgTexjBqiXxasNsMBxE0EgJDgVZ 1qvTQ73KJTHLr9IoHX/Pj0m7tFQTipFrP8nJx2GbImoTEqViWzA1geIqvDASUAV7vM +ENzkXK6/LfC06mFhrGKUdNnhyolF3zd4rIIglnMf0GZ1hjK3gM+J1fFpcbUG+4CWG XJoe/QUALN6PqGG7Syl6x/B0sD0B1ZWaXSmsLhrGxk6LawAJxlzXybFoIIfAPDtBpR zbyWHGNwHkECYMiDtDZZYtCvV0ewfV3aE9L+moj8DUp5rnTpUVn00vOpGp1fc2P/e0 4Ahrwsed2zNZw== From: Sasha Levin To: stable@vger.kernel.org Cc: Chris Mason , Jeff Layton , Chuck Lever , Sasha Levin Subject: [PATCH 6.1.y 4/4] SUNRPC: svcauth_gss: enforce krb5 token minimum length Date: Tue, 8 Sep 2026 13:55:45 -0400 Message-ID: <20260908175545.152676-4-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260908175545.152676-1-sashal@kernel.org> References: <2026090352-custard-sports-0e17@gregkh> <20260908175545.152676-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chris Mason [ Upstream commit a919c5c88769cf8fb3ec071e6078d830bf512489 ] 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") Cc: stable@vger.kernel.org Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260524010213.557424-2-cel@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin --- 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 74c1c17c7984f..c8c33f02a7ede 100644 --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -1003,6 +1003,8 @@ 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; -- 2.53.0