qvcimnfiqkwxudxmipassocorg send ietfdkim mailing list submissions gfkyhddlmipassocorg subscribe unsubscribe via world wide web visit httpmipassocorgmailmanlistinfoietfdkim via email send message subject body help qvcimnfiqkwxudxmipassocorg reach person managing list qghtrnrqbhlpvmipassocorg replying please edit subject line specific contents ietfdkim digest todays topics 1 dkim slashdotted frank ellermann 2 draftietfdkimoverview08 dkim slashdotted tony hansen 3 issue ssp02 discardable inappropriately specifies possible verifier action douglas otis 4 draftietfdkimoverview08 frank ellermann 5 dkim slashdotted jon callas 6 dkim slashdotted dave crocker 7 new issue policies required close security threats hector santos 8 new issue security threats well defined hector santos 9 new issue security threat unexpected third party senders hector santos 10 issue ssp02author signature scope narrow updates issue 1519 douglas otis 11 issue ssp02 mx record publishing mandate reduce dns overhead ssp discovery detect fraudulent messages douglas otis 12 issue ssp02 discardable inappropriately specifies possible verifier action hector santos gdqoxqxyzzyclaranetde sun feb 24 102727 2008 message 1 date mon 11 feb 2008 215416 0100 frank ellermann subject ietfdkim dkim slashdotted gfkyhddlmipassocorg messageid contenttype textplain charsetwindows1252 hi myths legends dkim check reading last dkim overview id think section starting historically start something else talks rfc 4408 4406 rfc 4407 fine summary key aspect rfc 2822 directly related ipbased decisions apart pra uses rfc 4406 ips enter picture prior work section ip based decisions asrg dnsbl draft could also referenced really historical prior art id expect note rfc 4870 comments slashdot far track wrt domainkeys date shown rfc 4870 example real dk example domainkeys older senderid whats worth imo age irrelevant ignoring needs patent trolls section 322 says openpgp modifies body email still necessarily case 44 typically verification done agent administrative management domain admd message recipient recipient mails mailboxes various admds doubt untypical one disadvantage term admd fine grained many typical scenarios section 5 uses relaying delivering admd better cases job done one admd third parties admds involved admd problems could eliminated adopting terms mon mrn sometimes fuzzier better identifying msa mon fine similar attempt wrt mda mrn smtp folks hit hard bat books write mda final delivery mta noted rfc 2821 local mail mda behind smtp please check mda definition eric bat book admittedly got wrong years 56 authoring organizations outbound service receiving organizations inbound service talking admds interesting cases services plural one service straight forward mediator mailing list often repost message without breaking dkim signature theory always problem might often case practice overview document mention issues moment sounds like commercial dkim reputation services potential rfc openpgp 2440bis draft rfc 4880 rfc 4870 listed referenced text curious folks likely also interested im part dkim history rfc 4870 dk part use emailarch terms mediator admd reference corresponding id slight differences a1 emailarch admds got didnt check frank nplyattcom sun feb 24 102727 2008 message 2 date mon 11 feb 2008 175557 0600 tony hansen subject ietfdkim draftietfdkimoverview08 dkim slashdotted frank ellermann cc gfkyhddlmipassocorg messageid 47b0e08d2030707attcom contenttype textplain charsetwindows1252 formatflowed thanks comments frank tony hansen nplyattcom frank ellermann wrote reading last dkim overview id think section starting historically start something else talks rfc 4408 4406 rfc 4407 fine summary key aspect rfc 2822 directly related ipbased decisions apart pra uses rfc 4406 ips enter picture prior work section ip based decisions asrg dnsbl draft could also referenced really historical prior art id expect note rfc 4870 comments slashdot far track wrt domainkeys date shown rfc 4870 example real dk example domainkeys older senderid whats worth imo age irrelevant ignoring needs patent trolls 44064408 references added set examples ip addresses content used determining identity section 322 says openpgp modifies body email still necessarily case 44 typically verification done agent administrative management domain admd message recipient recipient mails mailboxes various admds doubt untypical one disadvantage term admd fine grained many typical scenarios section 5 uses relaying delivering admd better cases job done one admd third parties admds involved admd problems could eliminated adopting terms mon mrn sometimes fuzzier better identifying msa mon fine similar attempt wrt mda mrn smtp folks hit hard bat books write mda final delivery mta noted rfc 2821 local mail mda behind smtp please check mda definition eric bat book admittedly got wrong years considered variations theme still came back see 56 authoring organizations outbound service receiving organizations inbound service talking admds interesting cases services plural one service straight forward mediator mailing list often repost message without breaking dkim signature theory always problem might often case practice overview document mention issues moment sounds like commercial dkim reputation services potential rfc openpgp 2440bis draft rfc 4880 rfc 4870 listed referenced text curious folks likely also interested im part dkim history rfc 4870 dk part thanks reminding us additional refs use emailarch terms mediator admd reference corresponding id slight differences a1 emailarch admds got didnt check timing king wed rather section expect go door emailarch yes two docs meant compatible tony hansen nplyattcom udcatmailabuseorg sun feb 24 102727 2008 message 3 date mon 11 feb 2008 153928 0800 douglas otis subject ietfdkim issue ssp02 discardable inappropriately specifies possible verifier action dkim list cc barry leiba messageid contenttype textplain charsetusascii formatflowed delspyes original protection sough rfc 5016 section 53 item 4 4 ssp must able publish expectation verifiable first party dkim signature expected receipt message support problem statement section 32 receivers standpoint knowing domain signs mail places high value receipt valid first party signature domain helpful assertion discardable resolve declared problem without also increasing chances email invalid signatures discarded rather rejected dsn generated even rfc 2821 frommail within domain response concerns expressed verifier handling implied discardable assertion steve atkins author similar draft coined term domains wish suffer reduction delivery integrity candidates use variant ssp needs scope see httpmipassocorgpipermailietfdkim2008q1009390html httptoolsietforghtmldraftlevineasp00 far soon establish even suggest discarding handling practice dkim signature failures discarding invalid signature early prolong incompatibility issues case discarding messages also eliminates evidence possible criminal activity counter effort eliminating type fraud httptoolsietforghtmldraftietfdkimssp02 33 ssp record syntax discardable mail domain signed author signature furthermore message arrives without valid author signature due modification transit submission via path without access signing key reason domain encourages recipients discard nonnormative discussion sender signing practices discardable would usually inappropriate domains end users potential mailing lists similar agents modify messages way render signature invalid domains sending mail expected pass significant modification recipient domains sending transactional messages appropriate places consider publication discardable practice see rfc5016 section 53 appendix discussion eliminate concerns related possible mishandling message eliminate reduction integrity delivery assurances term discardable needs changed change add sole mail domain signed intent avoid agents may damage remove signatures therefore domain represents sole entity assured provide signatures domains messages nonnormative discussion sender signing practices sole would usually inappropriate domains end users potential mailing lists similar agents modify messages way render signature invalid domains sending mail expected pass significant modification recipient domains sending transactional messages appropriate places consider publication sole practice see rfc5016 section 53 appendix discussion doug gdqoxqxyzzyclaranetde sun feb 24 102727 2008 message 4 date tue 12 feb 2008 005255 0100 frank ellermann subject ietfdkim draftietfdkimoverview08 gfkyhddlmipassocorg messageid contenttype textplain charsetwindows1252 tony hansen wrote timing king wed rather section expect go door emailarch informative reference id could good enough reference authenticationresults id checking emailarch pubreq found know state authheader id pubreq bookmarked yet read new authheader11 overview reference authheader authheader emailarch anyway one boat wrt timing frank aezcallasorg sun feb 24 102727 2008 message 5 date mon 11 feb 2008 160612 0800 jon callas subject ietfdkim dkim slashdotted frank ellermann cc gfkyhddlmipassocorg messageid contenttype textplain charsetusascii begin pgp signed message hash sha1 section 322 says openpgp modifies body email still necessarily case im sure know means jon begin pgp signature version pgp universal 263 charset usascii wj8dbqfhsol1stedwzod3gyraqo3aj0corfo3q2ha7168bfysqtkamk2aqcfy0pm memy7u0ldbfx1ap3jq2l30y tvcx end pgp signature otsdcrockernet sun feb 24 102727 2008 message 6 date mon 11 feb 2008 163506 0800 dave crocker subject ietfdkim dkim slashdotted jon callas cc gfkyhddlmipassocorg messageid 47b0e9ba9080608dcrockernet contenttype textplain charsetiso88591 formatflowed means applying pgp results body modified note beginend jon callas wrote begin pgp signed message hash sha1 section 322 says openpgp modifies body email still necessarily case im sure know means jon begin pgp signature version pgp universal 263 charset usascii wj8dbqfhsol1stedwzod3gyraqo3aj0corfo3q2ha7168bfysqtkamk2aqcfy0pm memy7u0ldbfx1ap3jq2l30y tvcx end pgp signature _______________________________________________ note well list operates according httpmipassocorgdkimietflistruleshtml dave crocker brandenburg internetworking bbiwnet mwbfbflsantronicscom sun feb 24 102727 2008 message 7 date mon 11 feb 2008 200642 0500 hector santos subject ietfdkim new issue policies required close security threats gfkyhddlmipassocorg messageid 47b0f12230901santronicscom contenttype textplain charsetiso88591 formatflowed recommend following changesnew text section 33 ssp record syntax 33 ssp record syntax ssp records must match taglist syntax defined rfc4871 specific tags used ssp records described unrecognized tags must ignored dkim outbound signing practices domain plaintext required possible values follows unknown domain may sign none email lack ssp record signifies unknown policy allows domain sign mail behalf author domain dkim protocol consistency check unknown policy optional author domain may sign none email policy different default dkimunknown policy allows domain sign dkimoptional policy optional author domain signing practice existence 3rd party signature contradicts dkim protocol consistency explicit domain policy therefore message rejected without prejudice mail domain signed domain signature message contradicts dkim protocol consistency explicit domain policy therefore message rejected without prejudice discardable mail domain signed author signature furthermore message arrives without valid author signature due modification transit submission via path without access signing key reason verifier must reject message without prejudice sincerely hector santos cto httpwwwsantronicscom httpsantronicsblogspotcom mwbfbflsantronicscom sun feb 24 102727 2008 message 8 date mon 11 feb 2008 200711 0500 hector santos subject ietfdkim new issue security threats well defined gfkyhddlmipassocorg messageid 47b0f13f7070008santronicscom contenttype textplain charsetiso88591 formatflowed section 5 pretty clear security threat potentials removed considerations ssp02 deal 5 security considerations security considerations sender signing practices mostly related attempts part malicious senders represent authors often attempt defraud either recipient alleged author additional security considerations regarding sender signing practices may found dkim threat analysis rfc4686 suggest following added part whole section clear present danger high potential frauds ignored gain payoff addvalued secured benefit signers verifiers users fraud exhibit transactions contradict following domain expectations mail expected optional 1st party signing strict 1st party signing 1st 3rd party signing required represent key propositions protocol consistency dkim model offer immediate high potential security protection current legacy domain forge abuses expected dkimadapting mail abuses please keep mind signature domain reputation evaluators fundamental dkim protocol consistency checks may viewed dkim policy declaration checking addition verifier mandated handling requirement handling language recommendations cited defined rfc2119 mail expected one largest abuse domains forged mail transactions using rfc2822 domains valid email hosting domains andor expected used email transaction principal owner domain protection offered ssp02 follows domains implicitly state mail expected creating null public key force invalidation signature augmenting dkimdiscardable enforces requirement valid signature therefore lack valid signature message rejected without prejudice optional 1st party signing conventional wisdom suggest domain explorers dkim test waters using optional 1st party signing policy messages signed others dont expect 3rd party signers test waters domain unexpected 3rd party signing protection offered via ssp02 new explicit policy dkimoptional recommended distinguishes current dkimunknown allows anyone sign misrepresent domain dkimoptional new policy declares domain signing practices optional expect domain sign mail 3rd party representation expected message containing 3rd party signature rejected without prejudice strict 1st party signing protection offered using dkimdiscardable message signature containing 3rd party signature rejected without prejudice 1st 3rd party signing required weak protection offered using dkimall weak allows inconsistent state exist without prejudice lacks handling semantics detectable inconsistent dkimall policy transaction message signature containing 3rd party signature may rejected without prejudice sincerely hector santos cto httpwwwsantronicscom httpsantronicsblogspotcom mwbfbflsantronicscom sun feb 24 102727 2008 message 9 date mon 11 feb 2008 200720 0500 hector santos subject ietfdkim new issue security threat unexpected third party senders gfkyhddlmipassocorg messageid 47b0f14890409santronicscom contenttype textplain charsetiso88591 formatflowed a4 third party senders another common use case third party enter agreement whereby third party send bulk mail behalf designated author domain using domain rfc2822 headers due many varied complexities agreements third party signing addressed specification authors anticipate mail systems gain experience dkim become possible codify best practices usages dkim fallacy common use case opinion stated limited insight based idea domains may wish part 3rd party bulk mailer system part prior 3rd party agreement inherent tos 3rd party signers besides obvious security fact introduces security threat email forgery misrepresentation reality majority domains internet intend participate 3rd party agreements wish represented 3rd party signers shape form regardless good bad intentions 3rd party exclusion 3rd party restrictions makes possible domain abused 3rd party misrepresentation proposed change a4 third party senders another common use case third party enter agreement whereby third party send bulk mail behalf designated author domain using domain rfc2822 headers however common use case potential open security hole 3rd party dkim signers misrepresentation domains secure potential security threat rfc2822 domain contains following ssp policies receiver honor policy semantics dkimdiscardable dkimoptional dkimdiscardable 1st party signing requirement dkimoptional 1st party signing option 3rd party signer expected policies therefore message containing 3rd party signature contradiction explicit domain signing practice policies author domain informing receiver message acceptable user delivery intend take responsibility harm caused accepting unexpected representation domain may rejected without prejudice lieu explicit ssp policies due unknown models available valid 3rd party arrangements unknowns models passed future 3rd party signing evaluators sincerely hector santos cto httpwwwsantronicscom httpsantronicsblogspotcom udcatmailabuseorg sun feb 24 102727 2008 message 10 date mon 11 feb 2008 181637 0800 douglas otis subject ietfdkim issue ssp02author signature scope narrow updates issue 1519 dkim list cc barry leiba messageid 21b1c88f82d04e8bbee879e61712e59bmailabuseorg contenttype textplain charsetusascii formatflowed delspyes see httpsrtpsgcomticketdisplayhtmlid1519 ssp02 28 author signature restrictive author signature valid signature identity user agent behalf message signed listed tag default value tag matches author address message structure draft changed strict reviewing draft definition used asp00 provides far less problematic author signature definition see httptoolsietforghtmldraftlevineasp00 28 author signature simple author signature valid signature signing domain listed tag present otherwise default value consisting value tag matches domain author address asp definition much better current ssp definition definitions better recognize signing domain authoritative messages compliant signing policy increased scope would allow greater freedom domains partition users separate subdomains different policies asserted emailaddress domain applies signature message indicates message compliant signing policies might desire limit scope compliance assure scope signatures compliance constrained keys g parameters key referenced could used author address well 28 author signature full scope author signature definition recommended author signature valid signature signing domain listed tag matches domain author address nonnormative discussion definition permits signatures localpart restricted keys subdomain restricted keys compliant assertion messages signed key restrictions limit domains authority indicate signature added listed tag limited scope author signature definition conservative author signature valid signature signing domain listed tag matches domain author address author address must also contained within scope key localpart subdomain range listed keys g tags nonnormative discussion key restrictions limit domains authority indicate signature added listed tag well limit ability restricted keys automatically considered compliant domains signing polices doug udcatmailabuseorg sun feb 24 102727 2008 message 11 date mon 11 feb 2008 192429 0800 douglas otis subject ietfdkim issue ssp02 mx record publishing mandate reduce dns overhead ssp discovery detect fraudulent messages dkim list cc barry leiba messageid 93ee93e3ad8d4fa69f5f336f49050a64mailabuseorg contenttype textplain charsetusascii formatflowed delspyes better ensure minimum number dns transactions occur processing dns ssp key txt records especially domains implement email ssp draft mandate publishing mx records whenever ssp record also published since ssp discovery process makes use mx record queries determine whether domain exists ssp record returned domain published mx record thereby signals email dkim used email addresses domain strategy affords better cache hit rate ssp discovery process detection fraudulent uses domain means protect second level domains 322 ssp lookup algorithm 4th 6th sentence purposes section valid ssp record one syntactically semantically correct particular must match abnf taglist must include defined dkim tag query may done parallel query made step 2 result query nxdomain error ssp checker must return appropriate error evaluator terminate algorithm 4th 6th sentence change purposes section valid ssp record one syntactically semantically correct particular must match abnf taglist must include defined dkim tag must accompanied mx record author domain query may done parallel query made step 2 result query nxdomain error ssp checker must return appropriate error evaluator terminate algorithm ssp record returned without also mx record author domain signature considered fraudulent without dns transactions attempted item 2 2 _verify domain exists_ ssp checker must perform dns query record corresponding author domain prefix type query type since step determine domain exists dns item 2 change 2 _verify domain exists_ ssp checker must perform dns query record corresponding author domain prefix type query mx record step depend upon record types response determine whether domain exists dns doug mwbfbflsantronicscom sun feb 24 102727 2008 message 12 date tue 12 feb 2008 023343 0500 hector santos subject ietfdkim issue ssp02 discardable inappropriately specifies possible verifier action douglas otis cc barry leiba dkim list messageid 47b14bd74000400santronicscom contenttype textplain charsetiso88591 formatflowed doug way read ssp02 mta verifiers longer picture rather muas muas would discarding discardable mail domain signed author signature furthermore message arrives without valid author signature due modification transit submission via path without access signing key reason domain encourages recipients discard reads recepients aka end users discarding whatever means semantics draft mta verifier handling therefore mta rejections concerns draft seems cater bulks mailers pushing mail pass mtas hope mta ignore dkim processing passing buck mua dkim market discardng whatever means play smtp rejectionbounce like concept sincerely hector santos cto httpwwwsantronicscom httpsantronicsblogspotcom douglas otis wrote original protection sough rfc 5016 section 53 item 4 4 ssp must able publish expectation verifiable first party dkim signature expected receipt message support problem statement section 32 receivers standpoint knowing domain signs mail places high value receipt valid first party signature domain helpful assertion discardable resolve declared problem without also increasing chances email invalid signatures discarded rather rejected dsn generated even rfc 2821 frommail within domain response concerns expressed verifier handling implied discardable assertion steve atkins author similar draft coined term domains wish suffer reduction delivery integrity candidates use variant ssp needs scope see httpmipassocorgpipermailietfdkim2008q1009390html httptoolsietforghtmldraftlevineasp00 far soon establish even suggest discarding handling practice dkim signature failures discarding invalid signature early prolong incompatibility issues case discarding messages also eliminates evidence possible criminal activity counter effort eliminating type fraud httptoolsietforghtmldraftietfdkimssp02 33 ssp record syntax discardable mail domain signed author signature furthermore message arrives without valid author signature due modification transit submission via path without access signing key reason domain encourages recipients discard nonnormative discussion sender signing practices discardable would usually inappropriate domains end users potential mailing lists similar agents modify messages way render signature invalid domains sending mail expected pass significant modification recipient domains sending transactional messages appropriate places consider publication discardable practice see rfc5016 section 53 appendix discussion eliminate concerns related possible mishandling message eliminate reduction integrity delivery assurances term discardable needs changed change add sole mail domain signed intent avoid agents may damage remove signatures therefore domain represents sole entity assured provide signatures domains messages nonnormative discussion sender signing practices sole would usually inappropriate domains end users potential mailing lists similar agents modify messages way render signature invalid domains sending mail expected pass significant modification recipient domains sending transactional messages appropriate places consider publication sole practice see rfc5016 section 53 appendix discussion doug _______________________________________________ note well list operates according tohttpmipassocorgdkimietflistruleshtml _______________________________________________ note well list operates according end ietfdkim digest vol 107 issue 2 tue 05 aug 2008 183041 0800 ietfdkim digest vol 107 issue 2