[strongSwan] IKEv2 rekey failure with IOS8

[Tom Matthews]

> On 23 Jul 2015, at 18:10, Tobias Brunner <tobias at strongswan.org> wrote:
> but more correctly you'd define that as prfsha256 in the IKE proposal instead.

Noted, I’ve updated the IKE proposal accordingly.

> You saw that the proposal by the iOS 8 client does not contain a DH
> group.  This is actually not RFC 7296 (IKEv2) compliant. So this looks like a bug in iOS 8 to me.

It also sounds like my suspicions about lack of PFS support in IOS8.3 are confirmed.

> The iOS 8 IKEv2 client can handle a single proposal for ESP, which can
> be changed with the ChildSecurityAssociationParameters in the profile.
> You obviously already did specify that to use AES-GCM.  If the proposal
> in your profile actually includes a DiffieHellmanGroup key with the
> value set to 16 then this looks like another bug.

Indeed, the mobileconfig I used on the IOS device contains the supposedly supported child DH param '16' :
          <key>ChildSecurityAssociationParameters</key>
          <dict>
            <key>EncryptionAlgorithm</key>
            <string>AES-256-GCM</string>
            <key>IntegrityAlgorithm</key>
            <string>SHA2-256</string>
            <key>DiffieHellmanGroup</key>
            <integer>16</integer>
            <key>LifeTimeInMinutes</key>
            <integer>720</integer>
          </dict>

> Does the same happen if the client initiates the rekeying?  Does the
> behavior change if you don't use AES-GCM?

I tried getting the IOS8 client to do a rekey by using this config, as there’s no way to force a rekey on the device AFAIK :

        keylife=5m
        rekeymargin=1m
        rekey=no

But a rekey attempt from the IOS8 device hasn’t happened yet, I’ll leave it a few hours and see what happens, but in the meantime
I am satisfied to discover that IOS8 cannot handle rekey from the server, and cannot seemingly support PFS.

Kind regards and thank you for your attention on this matter,
Tom
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