(In)valid RSA key?

[Matt Johnston]

Hi.

In testing my SSH 2 server implementation (Dropbear), I've come across
certain RSA hostkeys which fail for use with PuTTY as a client. Converting
the keys for use with OpenSSH they also fail with PuTTY, which leads me to
wonder whether they are valid keys or not.

A sample key is attached, the important point to note is that the modulus
(n) value doesn't have a multiple-of-8 number of bits. Is there any
restriction on this? I haven't been able to find it specified anywhere.

The actual values are as follows:

n = 5886038905939931849793481926512875796836831719086734501519439860867912043790433262172630182697151131061148053854157155928712160937159068340118524813331816081025146309669009627549904578599602238492945297625461197628827141251138070043885227519045851919271348006113851652031006020294214266581123496032014041406270211

e = 65537

d = 2126220075060224706837525231979886500973727117775597793444485088822908429203270168739412041215990293677489342309585676937551790561458470541586675563892418233675380406419737033970559160285418583461017508368164937992703260549775879495018447997717953682981971642011940066077145681062355607163288549105412107221295137

p = 3428173739317616181988534253356424530886922795123777038960838820205861975510242373349759813680387393140772490491315664543565449716768374690346649042484853257

q = 1716960502448617995898088425791227141403238670199393648351700681159719711393276881945477576191000645095022170651697097981764516876134433284745878926818602923

Any advice would be appreciated.

Cheers,
Matt Johnston
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-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----