Begin forwarded message: Date: Wed, 10 Jun 2020 09:32:26 +0000 From: bugzilla-dae...@bugzilla.kernel.org To: step...@networkplumber.org Subject: [Bug 208121] New: IPsec AH ICV Padding for IPv4 https://bugzilla.kernel.org/show_bug.cgi?id=208121 Bug ID: 208121 Summary: IPsec AH ICV Padding for IPv4 Product: Networking Version: 2.5 Kernel Version: 5.4.0.37.40 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Other Assignee: step...@networkplumber.org Reporter: markus.gas...@elektrobit.com Regression: No Created attachment 289597 --> https://bugzilla.kernel.org/attachment.cgi?id=289597&action=edit packet capture According to RFC 4302[1]: > As mentioned in Section 2.6, the ICV field may include explicit > padding if required to ensure that the AH header is a multiple of 32 > bits (IPv4) or 64 bits (IPv6). If padding is required, its length is > determined by two factors: > > - the length of the ICV > - the IP protocol version (v4 or v6) [...] > Inclusion of padding in excess of the minimum amount required to > satisfy IPv4/IPv6 alignment requirements is prohibited. However, in the Linux implementation padding is always added (and expected) so that the Authentication Header (AH) is a multiple of 64 bits, independent of the IP version used. This is an issue when the IPsec AH with IPv4 is used with HMAC authentication e.g. HMAC-sha256-128. In this case the ICV field is 128 bits long, which results in an AH length of 96 + 128 = 224 bits. Even though this is a multiple of 32 bits, Linux adds an additional 32 bits of padding. Additionally, Linux drops incoming packets that do not have this padding. In the attached file the outgoing packets, that are wrongfully padded can be seen. [1] https://tools.ietf.org/html/rfc4302#section-3.3.3.2.1 -- You are receiving this mail because: You are the assignee for the bug.
