DSS es un esquema de firma digital publicado (pero no inventado) por la NSA. En TLS ( TLS1.0 , PKIX ) cumple la misma función que RSA y ECDSA: las firmas digitales prueban que el servidor con el que está hablando tiene la clave privada correspondiente a la clave pública en El certificado y que la información en el certificado (incluida la clave pública del servidor) es exactamente lo que la CA revisó y aprobó.
Por razones que no conozco, en la práctica, el DSS en TLS perdió un concurso de popularidad con RSA y se extinguió. No pude encontrar una CA que vende certificados DSS. OpenSSL (incluido Android), MSIE y Java siguen siendo compatibles con TLS_DHE_DSS_WITH_AES_128_CBC_SHA (0x0032), pero Chrome, Firefox y Safari (de escritorio y móvil) no lo hacen, por lo que es bastante inútil.
El algoritmo DSA está vivo y bien, pero en estos días se usa con curvas elípticas, en cuyo caso se llama ECDSA . Se prefiere RSA por razones de rendimiento y es utilizado por Google y CloudFlare, si el cliente lo admite. CAs le venderá certificados ECDSA.
DSA y ECDSA tienen la falla de que requieren una nueva función aleatoria para cada operación de señalización y, si no es lo suficientemente aleatoria, la firma expone la clave privada (!). Las firmas digitales deterministas se desarrollaron para no requerir buenos valores aleatorios para las operaciones de señalización.
Un algoritmo de firma digital determinista rápido y seguro llamado EdDSA, en particular ed25519, recientemente se hizo popular (utilizado en las versiones más recientes de openssh y un montón de nuevas herramientas de cifrado). El CFRG debería, eventualmente, recomendar claves y certificados EdDSA para TLS, junto con El intercambio de claves de Curve25519, por lo que TLS_CURVE25519_ED25519_CHACHA20_POLY1305 se convertirá en el conjunto de claves recomendado para TLS 1.3 y DJB podrá declarar la victoria y retirarse.
He dicho que la prueba del servidor SSL de Qualys dice que "DHE_DSS no se puede usar para PFS porque requieren claves DSS , que efectivamente se limitan a 1024 bits ".
Para el experimento, he configurado Apache 2.4.7 con OpenSSL 1.0.1f para usar DHE_DSS_AES128_CBC y DHE_RSA_AES128_CBC. El certificado RSA es real, mientras que el certificado DSS es autofirmado, pero esto no importa para el propósito de este ejercicio.
Me conecté desde 192.168.1.101 al servidor que se ejecuta en 192.168.1.103 con OpenSSL 1.0.1m (openssl s_client), grabé el protocolo de enlace y exporté una disección con WireShark.
Ambas configuraciones funcionaron, por lo que al menos entre dos OpenSSL 1.0.1, 2048 bit DSA keys funcionan. Por supuesto, esto no significa que desee utilizar un certificado DSS para un sitio web, incluso si pudiera comprar uno.
Disección de saludo de DHE RSA:
Protocolo de Internet versión 4, Src: 192.168.1.101 (192.168.1.101), Dst: 192.168.1.103 (192.168.1.103)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Client Hello
Content Type: Handshake (22)
Version: TLS 1.0 (0x0301)
Length: 94
Handshake Protocol: Client Hello
Handshake Type: Client Hello (1)
Length: 90
Version: TLS 1.2 (0x0303)
Random
Session ID Length: 0
Cipher Suites Length: 4
Cipher Suites (2 suites)
Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033)
Cipher Suite: TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00ff)
Compression Methods Length: 1
Compression Methods (1 method)
Extensions Length: 45
Extension: SessionTicket TLS
Extension: signature_algorithms
Extension: Heartbeat
Protocolo de Internet versión 4, Src: 192.168.1.103 (192.168.1.103), Dst: 192.168.1.101 (192.168.1.101)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Server Hello
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 58
Handshake Protocol: Server Hello
Handshake Type: Server Hello (2)
Length: 54
Version: TLS 1.2 (0x0303)
Random
Session ID Length: 0
Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033)
Compression Method: null (0)
Extensions Length: 14
Extension: renegotiation_info
Extension: SessionTicket TLS
Extension: Heartbeat
Protocolo de Internet versión 4, Src: 192.168.1.103 (192.168.1.103), Dst: 192.168.1.101 (192.168.1.101)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Certificate
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 1630
Handshake Protocol: Certificate
Handshake Type: Certificate (11)
Length: 1626
Certificates Length: 1623
Certificates (1623 bytes)
Certificate Length: 1620
Certificate (pkcs-9-at-emailAddress=5b2ca5a024054a47bfcc565a8737db21.protect,id-at-commonName=www.zeev.pw,id-at-countryName=IL)
signedCertificate
version: v3 (2)
serialNumber: 1127576
signature (sha256WithRSAEncryption)
Algorithm Id: 1.2.840.113549.1.1.11 (sha256WithRSAEncryption)
issuer: rdnSequence (0)
rdnSequence: 4 items (id-at-commonName=StartCom Class 1 Primary Intermediate Server C,id-at-organizationalUnitName=Secure Digital Certificate Signing,id-at-organizationName=StartCom Ltd.,id-at-countryName=IL)
RDNSequence item: 1 item (id-at-countryName=IL)
RelativeDistinguishedName item (id-at-countryName=IL)
Id: 2.5.4.6 (id-at-countryName)
CountryName: IL
RDNSequence item: 1 item (id-at-organizationName=StartCom Ltd.)
RelativeDistinguishedName item (id-at-organizationName=StartCom Ltd.)
Id: 2.5.4.10 (id-at-organizationName)
DirectoryString: printableString (1)
printableString: StartCom Ltd.
RDNSequence item: 1 item (id-at-organizationalUnitName=Secure Digital Certificate Signing)
RelativeDistinguishedName item (id-at-organizationalUnitName=Secure Digital Certificate Signing)
Id: 2.5.4.11 (id-at-organizationalUnitName)
DirectoryString: printableString (1)
printableString: Secure Digital Certificate Signing
RDNSequence item: 1 item (id-at-commonName=StartCom Class 1 Primary Intermediate Server C)
RelativeDistinguishedName item (id-at-commonName=StartCom Class 1 Primary Intermediate Server CA)
Id: 2.5.4.3 (id-at-commonName)
DirectoryString: printableString (1)
printableString: StartCom Class 1 Primary Intermediate Server CA
validity
notBefore: utcTime (0)
notAfter: utcTime (0)
subject: rdnSequence (0)
rdnSequence: 3 items (pkcs-9-at-emailAddress=5b2ca5a024054a47bfcc565a8737db21.protect,id-at-commonName=www.zeev.pw,id-at-countryName=IL)
RDNSequence item: 1 item (id-at-countryName=IL)
RelativeDistinguishedName item (id-at-countryName=IL)
Id: 2.5.4.6 (id-at-countryName)
CountryName: IL
RDNSequence item: 1 item (id-at-commonName=www.zeev.pw)
RelativeDistinguishedName item (id-at-commonName=www.zeev.pw)
Id: 2.5.4.3 (id-at-commonName)
DirectoryString: printableString (1)
printableString: www.zeev.pw
RDNSequence item: 1 item (pkcs-9-at-emailAddress=5b2ca5a024054a47bfcc565a8737db21.protect)
RelativeDistinguishedName item (pkcs-9-at-emailAddress=5b2ca5a024054a47bfcc565a8737db21.protect@whoisguard.com)
Id: 1.2.840.113549.1.9.1 (pkcs-9-at-emailAddress)
IA5String: [email protected]
subjectPublicKeyInfo
algorithm (rsaEncryption)
Algorithm Id: 1.2.840.113549.1.1.1 (rsaEncryption)
Padding: 0
subjectPublicKey: 3082010a0282010100c1c8ada6e3526a74da3f873b2352be...
extensions: 10 items
algorithmIdentifier (sha256WithRSAEncryption)
Algorithm Id: 1.2.840.113549.1.1.11 (sha256WithRSAEncryption)
Padding: 0
encrypted: 54980c6f342bc4de5641df814fe88634ec110461e260e212...
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Server Key Exchange
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 783
Handshake Protocol: Server Key Exchange
Handshake Type: Server Key Exchange (12)
Length: 779
Diffie-Hellman Server Params
p Length: 256
p: ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd1...
g Length: 1
g: 02
Pubkey Length: 256
Pubkey: 606134278d8b25b3367d3e15b2b46a3419cbe596721d446d...
Signature Hash Algorithm: 0x0601
Signature Hash Algorithm Hash: SHA512 (6)
Signature Hash Algorithm Signature: RSA (1)
Signature Length: 256
Signature: 48b69b547860511e36830041f7e7aee3d97ced1144f190d4...
TLSv1.2 Record Layer: Handshake Protocol: Server Hello Done
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 4
Handshake Protocol: Server Hello Done
Handshake Type: Server Hello Done (14)
Length: 0
Protocolo de Internet versión 4, Src: 192.168.1.101 (192.168.1.101), Dst: 192.168.1.103 (192.168.1.103)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Client Key Exchange
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 262
Handshake Protocol: Client Key Exchange
Handshake Type: Client Key Exchange (16)
Length: 258
Diffie-Hellman Client Params
Pubkey Length: 256
Pubkey: 020621c1846fa567392b2fa1b55868a65389400ee80f3594...
TLSv1.2 Record Layer: Change Cipher Spec Protocol: Change Cipher Spec
Content Type: Change Cipher Spec (20)
Version: TLS 1.2 (0x0303)
Length: 1
Change Cipher Spec Message
TLSv1.2 Record Layer: Handshake Protocol: Encrypted Handshake Message
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 64
Handshake Protocol: Encrypted Handshake Message
Protocolo de Internet versión 4, Src: 192.168.1.103 (192.168.1.103), Dst: 192.168.1.101 (192.168.1.101)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: New Session Ticket
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 202
Handshake Protocol: New Session Ticket
Handshake Type: New Session Ticket (4)
Length: 198
TLS Session Ticket
TLSv1.2 Record Layer: Change Cipher Spec Protocol: Change Cipher Spec
Content Type: Change Cipher Spec (20)
Version: TLS 1.2 (0x0303)
Length: 1
Change Cipher Spec Message
TLSv1.2 Record Layer: Handshake Protocol: Encrypted Handshake Message
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 64
Handshake Protocol: Encrypted Handshake Message
Disección del protocolo DHE DSS:
Protocolo de Internet versión 4, Src: 192.168.1.101 (192.168.1.101), Dst: 192.168.1.103 (192.168.1.103)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Client Hello
Content Type: Handshake (22)
Version: TLS 1.0 (0x0301)
Length: 94
Handshake Protocol: Client Hello
Handshake Type: Client Hello (1)
Length: 90
Version: TLS 1.2 (0x0303)
Random
Session ID Length: 0
Cipher Suites Length: 4
Cipher Suites (2 suites)
Cipher Suite: TLS_DHE_DSS_WITH_AES_128_CBC_SHA (0x0032)
Cipher Suite: TLS_EMPTY_RENEGOTIATION_INFO_SCSV (0x00ff)
Compression Methods Length: 1
Compression Methods (1 method)
Extensions Length: 45
Extension: SessionTicket TLS
Extension: signature_algorithms
Extension: Heartbeat
Protocolo de Internet versión 4, Src: 192.168.1.103 (192.168.1.103), Dst: 192.168.1.101 (192.168.1.101)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Server Hello
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 58
Handshake Protocol: Server Hello
Handshake Type: Server Hello (2)
Length: 54
Version: TLS 1.2 (0x0303)
Random
Session ID Length: 0
Cipher Suite: TLS_DHE_DSS_WITH_AES_128_CBC_SHA (0x0032)
Compression Method: null (0)
Extensions Length: 14
Extension: renegotiation_info
Extension: SessionTicket TLS
Extension: Heartbeat
TLSv1.2 Record Layer: Handshake Protocol: Certificate
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 1180
Handshake Protocol: Certificate
Handshake Type: Certificate (11)
Length: 1176
Certificates Length: 1173
Certificates (1173 bytes)
Certificate Length: 1170
Certificate (id-at-commonName=zeev.pw,id-at-organizationName=Internet Widgits Pty Ltd,id-at-stateOrProvinceName=Some-State,id-at-countryName=US)
signedCertificate
serialNumber: -5833175930474264775
signature (joint-iso-itu-t.16.840.1.101.3.4.3.2)
Algorithm Id: 2.16.840.1.101.3.4.3.2 (joint-iso-itu-t.16.840.1.101.3.4.3.2)
issuer: rdnSequence (0)
rdnSequence: 4 items (id-at-commonName=zeev.pw,id-at-organizationName=Internet Widgits Pty Ltd,id-at-stateOrProvinceName=Some-State,id-at-countryName=US)
RDNSequence item: 1 item (id-at-countryName=US)
RelativeDistinguishedName item (id-at-countryName=US)
Id: 2.5.4.6 (id-at-countryName)
CountryName: US
RDNSequence item: 1 item (id-at-stateOrProvinceName=Some-State)
RelativeDistinguishedName item (id-at-stateOrProvinceName=Some-State)
Id: 2.5.4.8 (id-at-stateOrProvinceName)
DirectoryString: uTF8String (4)
uTF8String: Some-State
RDNSequence item: 1 item (id-at-organizationName=Internet Widgits Pty Ltd)
RelativeDistinguishedName item (id-at-organizationName=Internet Widgits Pty Ltd)
Id: 2.5.4.10 (id-at-organizationName)
DirectoryString: uTF8String (4)
uTF8String: Internet Widgits Pty Ltd
RDNSequence item: 1 item (id-at-commonName=zeev.pw)
RelativeDistinguishedName item (id-at-commonName=zeev.pw)
Id: 2.5.4.3 (id-at-commonName)
DirectoryString: uTF8String (4)
uTF8String: zeev.pw
validity
notBefore: utcTime (0)
notAfter: utcTime (0)
subject: rdnSequence (0)
rdnSequence: 4 items (id-at-commonName=zeev.pw,id-at-organizationName=Internet Widgits Pty Ltd,id-at-stateOrProvinceName=Some-State,id-at-countryName=US)
RDNSequence item: 1 item (id-at-countryName=US)
RelativeDistinguishedName item (id-at-countryName=US)
Id: 2.5.4.6 (id-at-countryName)
CountryName: US
RDNSequence item: 1 item (id-at-stateOrProvinceName=Some-State)
RelativeDistinguishedName item (id-at-stateOrProvinceName=Some-State)
Id: 2.5.4.8 (id-at-stateOrProvinceName)
DirectoryString: uTF8String (4)
uTF8String: Some-State
RDNSequence item: 1 item (id-at-organizationName=Internet Widgits Pty Ltd)
RelativeDistinguishedName item (id-at-organizationName=Internet Widgits Pty Ltd)
Id: 2.5.4.10 (id-at-organizationName)
DirectoryString: uTF8String (4)
uTF8String: Internet Widgits Pty Ltd
RDNSequence item: 1 item (id-at-commonName=zeev.pw)
RelativeDistinguishedName item (id-at-commonName=zeev.pw)
Id: 2.5.4.3 (id-at-commonName)
DirectoryString: uTF8String (4)
uTF8String: zeev.pw
subjectPublicKeyInfo
algorithm (id-dsa)
Algorithm Id: 1.2.840.10040.4.1 (id-dsa)
DSS-Params
p : 0x009f922489033a4317d074675e70a4573184f810a441e7c373ea2562dcadb93f636393453bc144c57e773a8f66e58274663cf3fd5c2588aee86d36104e83a81cbc47704d623662e7b48d620315c3145ed0313397b58bd84494ad2b02c2c3124648ca29e490bb81a5a2d1fc52900ccc1c511256690
q : 0x00dac80ee885e74b0e56d9cac7d9a6e0efaaf5155bfb2e1426d99a0d4235d60359
g : 0x55234ba34d71468ff4c90a06c74ddebc0b882f0f77efadf45e1fc5ede292d31b19457746555616318755e5fdc5819041c16c6c2cbd8d9af9eca62046d533e232591596b9e74adb05662f66f72009e6f7742f81c35bdbf7c2ebb249a6aa9cf20a6c330b8dd214835d6aa2e330cb2b4a866a74ff438
Padding: 0
subjectPublicKey: 028201001fea1029b1edbbb83e8b92a56f4c34926a617fcd...
algorithmIdentifier (joint-iso-itu-t.16.840.1.101.3.4.3.2)
Algorithm Id: 2.16.840.1.101.3.4.3.2 (joint-iso-itu-t.16.840.1.101.3.4.3.2)
Padding: 0
encrypted: 304402201d495bb07b7e000bd5c4b4f0a9b6a9183cbef0cf...
Protocolo de Internet versión 4, Src: 192.168.1.103 (192.168.1.103), Dst: 192.168.1.101 (192.168.1.101)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Server Key Exchange
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 598
Handshake Protocol: Server Key Exchange
Handshake Type: Server Key Exchange (12)
Length: 594
Diffie-Hellman Server Params
p Length: 256
p: ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd1...
g Length: 1
g: 02
Pubkey Length: 256
Pubkey: da0d4624e78f6f72d08f973ff3482bc92c758b6cb86b1812...
Signature Hash Algorithm: 0x0602
Signature Hash Algorithm Hash: SHA512 (6)
Signature Hash Algorithm Signature: DSA (2)
Signature Length: 71
Signature: 3045022057fc39446c326c9b3e5f3f0f08e161daa45823a1...
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Server Hello Done
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 4
Handshake Protocol: Server Hello Done
Handshake Type: Server Hello Done (14)
Length: 0
Protocolo de Internet versión 4, Src: 192.168.1.101 (192.168.1.101), Dst: 192.168.1.103 (192.168.1.103)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: Client Key Exchange
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 262
Handshake Protocol: Client Key Exchange
Handshake Type: Client Key Exchange (16)
Length: 258
Diffie-Hellman Client Params
Pubkey Length: 256
Pubkey: 8060234a6b4dee8a815d648df47b020b5f24ab800b20bd4b...
TLSv1.2 Record Layer: Change Cipher Spec Protocol: Change Cipher Spec
Content Type: Change Cipher Spec (20)
Version: TLS 1.2 (0x0303)
Length: 1
Change Cipher Spec Message
TLSv1.2 Record Layer: Handshake Protocol: Encrypted Handshake Message
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 64
Handshake Protocol: Encrypted Handshake Message
Protocolo de Internet versión 4, Src: 192.168.1.103 (192.168.1.103), Dst: 192.168.1.101 (192.168.1.101)
Capa de sockets seguros
TLSv1.2 Record Layer: Handshake Protocol: New Session Ticket
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 202
Handshake Protocol: New Session Ticket
Handshake Type: New Session Ticket (4)
Length: 198
TLS Session Ticket
TLSv1.2 Record Layer: Change Cipher Spec Protocol: Change Cipher Spec
Content Type: Change Cipher Spec (20)
Version: TLS 1.2 (0x0303)
Length: 1
Change Cipher Spec Message
TLSv1.2 Record Layer: Handshake Protocol: Encrypted Handshake Message
Content Type: Handshake (22)
Version: TLS 1.2 (0x0303)
Length: 64
Handshake Protocol: Encrypted Handshake Message