如何验证 HTTP 重定向绑定的 SAML 签名 [英] How to verify a SAML signature for HTTP-redirect binding
问题描述
我通过 HTTP 重定向绑定接收 SAML 请求，SAML 请求的内容如下所示
<块引用>{"SigAlg"=>"http://www.w3.org/2000/09/xmldsig#rsa-sha1",SAMLRequest"=> lVLLaoQwFP0VyT5jEqPG4AiFoSDMtNApXXQzxDxaQRObRDqfX3XoolAKXd7DPQ/uuXUQ4zDxo3tzc3zSH7MOMWkPe3DpcixzVVVQl4RBqoiCncEYEmkoY7k00hCQvGgfemf3gOwQSNoQZt3aEIWNC4RwCRGGiD6jkmPMs2KHUPYKksPi0lsRN + Z7jFPgafqpvejtbtQpSK7jYAPfsu3B7C13IvSBWzHqwKPk57vTkS + WfPIuOukG0NSbub9R/yaJELRfzUGzrhmtFut15qdeeheciY926K2u05toUz8sIu0huXd + FPFv9RXpFTTbKp/WA4WobQT/jEYrykwhNaQ66yDNMwY7wijEtMCmysqqo6xOb8Ga + tbjWYe1jtYqfW0uCucoYwWCHS3F0kRGoajWTpAiiJRZJRmu01 + Y3 + CPt2i + AA =="}
它也有一个签名值
<块引用>WkDaGzC6vPTlzh + EnFA5/8IMmV7LviyRh2DA5EHF0K0nl + xzBlKfNCYRnunpwoEvGhereGdI5xBpv + mc9IguiCaLZSZjDh6lIDdpvctCnmSNzORqzWQwQGeZ9vjgtCLjUn35VZLNs3WgEqbi2cL + ObrUDS2gV1XvBA3Q3RRhoDmi + XE89Ztnd1cNpR3XdA + EL2ENbMI2XAD9qSgMufUJY/3GBBpT7Vg1ODtPxBudq + sXrgPh/+ + WtUUitLkkfC8tdRTCS1EZPv h27I5g/VNza23Xl8w2HdAuYP0F2FjREo8VV2aUtaOUd/jAF9 + bfkGV93y1PzFttLxdBbFoxp6qBg ==
但我不明白如何验证此签名是否正确.
关于 SAML 绑定的第 3.4.4.1 节 https://docs.oasis-open.org/security/saml/v2.0/saml-bindings-2.0-os.pdf
要构造签名，一个由 RelayState 串联组成的字符串(如果存在)，SigAlg 和 SAMLRequest(或 SAMLResponse)查询字符串参数(每一个 URLencoded)以下列方式之一构造(按以下顺序排列):SAMLRequest=value&RelayState=value&SigAlg=valueSAMLResponse=value&RelayState=value&SigAlg=value我尝试了这种方法，但
我使用私钥生成的签名与我从 SP 收到的签名不匹配.(贴在上面)
此外，我无法使用私钥解密签名的消息(我假设签名是使用我与之联合的公共创建的.)
<samlp:LogoutRequest ID="_36167d94-d868-4c04-aee3-8bbd4ed91317" Version="2.0" IssueInstant="2017-01-05T16:21:55.704Z" Destination="https://werain.me/" xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"><Issuer xmlns="urn:oasis:names:tc:SAML:2.0:assertion">urn:federation:MicrosoftOnline</Issuer><NameID Format="urn:oasis:names:tc:SAML:2.0:nameid-format:persistent" xmlns="urn:oasis:names:tc:SAML:2.0:assertion">4948f6ce-4e3b-4538-b284-1461f9379b48</NameID><samlp:SessionIndex>_eafbb730-b590-9210-180-b590-9210-130-130-1000;/samlp:LogoutRequest>这里有任何帮助.
SAML 身份验证消息是带有嵌入(封装)XMLDSig 签名或压缩的编码签名的 XML 文档
封装的 XMLDSign 签名
<...saml 消息...><ds:签名><ds:SignedInfo/><ds:SignatureValue/><ds:KeyInfo/></ds:签名></samlp:LogoutRequest>
URL 中的压缩编码
SAMLRequest=value&RelayState=value&SigAlg=value&Signature=value其中每个值都是 url 编码的
SAMLRequest=urlencode(base64(<samlp:LogoutRequest> <...saml message...> </samlp:LogoutRequest>))并且签名是使用算法SigAlg
Signature = urlencode( base64 ( SigAlg ("SAMLRequest=value&RelayState=value&SigAlg=value")))SAML 消息的数字签名
SAML 消息使用发行者 (SP) 的私钥进行数字签名(未加密)，并且可以使用 SP 的公钥进行验证.SAML 响应必须使用身份提供商 (IdP) 的私钥进行签名，SP 可以使用 IdP 的公钥验证消息.
如果您作为 IdP 并且想要验证 SP 的 SAML 请求，您需要:
验证数字签名:使用SP的公钥验证签名与签名的消息匹配，以确保签名者的身份和消息没有被篡改>
授权请求:验证签名者的身份是否可以执行请求的操作.通常，您必须将证书的序列号或主题与预先存在的列表进行匹配，或者验证证书是否由受信任的证书颁发机构颁发
生成 SAML 响应:生成包含 SAML 数据的 XML 消息，并使用您的私钥对其进行签名以发送给 SP
大多数编程语言都支持 XMLDsig 签名，但在您的情况下使用的是 deflated 编码g，这是 SAML 绑定的特定特征，因此如果您的 SAML 库不支持它，您有手动验证签名.根据 规格
//从查询字符串中获取参数String samlrequest = getQueryParam("SAMLRequest");String relaystate = getQueryParam("RelayState");String sigalg = getQueryParam("SigAlg");String signature = getQueryParam("Signature");//签名字节签名[] = URLDecoder.decode(Base64.getDecoder().decode(signature), "UTF-8");//签名数据.构建以下字符串检查 RelayState 是否为空//SAMLRequest=samlrequest&RelayState=relaystate&SigAlg=sigalgbyte signedData[] = concat(samlrequest,relaystate,sigalg);//签名算法可以是SHA1WithRSA"或SHA1withDSA"，具体取决于sigalg是http://www.w3.org/2000/09/xmldsig#rsa-sha1或http://www.w3.org/2000/09/xmldsig#dsa-sha1String signatureAlgorithm = extractSignatureAlgorithm(sigalg);//获取SP的公钥.必须在此过程之前注册公钥 publicKey = ...//验证签名签名 sig = Signature.getInstance(signatureAlgorithm);sig.initVerify(publicKey);sig.update(signedData);布尔验证 = sig.verify(signature);I'm receiving a SAML request via HTTP-redirect binding the content of the SAML request look like this
{"SigAlg"=>"http://www.w3.org/2000/09/xmldsig#rsa-sha1", "SAMLRequest"=>"lVLLaoQwFP0VyT5jEqPG4AiFoSDMtNApXXQzxDxaQRObRDqfX3XoolAKXd7DPQ/uuXUQ4zDxo3tzc3zSH7MOMWkPe3DpcixzVVVQl4RBqoiCncEYEmkoY7k00hCQvGgfemf3gOwQSNoQZt3aEIWNC4RwCRGGiD6jkmPMs2KHUPYKksPi0lsRN+Z7jFPgafqpvejtbtQpSK7jYAPfsu3B7C13IvSBWzHqwKPk57vTkS+WfPIuOukG0NSbub9R/yaJELRfzUGzrhmtFut15qdeeheciY926K2u05toUz8sIu0huXd+FPFv9RXpFTTbKp/WA4WobQT/jEYrykwhNaQ66yDNMwY7wijEtMCmysqqo6xOb8Ga+tbjWYe1jtYqfW0uCucoYwWCHS3F0kRGoajWTpAiiJRZJRmu01+Y3+CPt2i+AA=="}
It also has a Signature value
WkDaGzC6vPTlzh+EnFA5/8IMmV7LviyRh2DA5EHF0K0nl+xzBlKfNCYRnunpwoEvGhereGdI5xBpv+mc9IguiCaLZSZjDh6lIDdpvctCnmSNzORqzWQwQGeZ9vjgtCLjUn35VZLNs3WgEqbi2cL+ObrUDS2gV1XvBA3Q3RRhoDmi+XE89Ztnd1cNpR3XdA+EL2ENbMI2XAD9qSgMufUJY/3GBBpT7Vg1ODtPxBudq+sXrgPh/+WtUUitLkkfC8tdRTCS1EZPv+h27I5g/VNza23Xl8w2HdAuYP0F2FjREo8VV2aUtaOUd/jAF9+bfkGV93y1PzFttLxdBbFoxp6qBg==
But I fail to understand how to verify this signature is correct.
Section 3.4.4.1 on SAML binding https://docs.oasis-open.org/security/saml/v2.0/saml-bindings-2.0-os.pdf
To construct the signature, a string consisting of the concatenation of the RelayState (if present),
SigAlg, and SAMLRequest (or SAMLResponse) query string parameters (each one URLencoded)
is constructed in one of the following ways (ordered as below):
SAMLRequest=value&RelayState=value&SigAlg=value
SAMLResponse=value&RelayState=value&SigAlg=value
I tried the approach but
The signature I generated using the Private key does not match to the one I received from my SP. (posted above)
Also, I'm not able to decrypt the signed message using the Private key (I'm assuming the Signature was created using the public that I federated it with.)
<samlp:LogoutRequest ID="_36167d94-d868-4c04-aee3-8bbd4ed91317" Version="2.0" IssueInstant="2017-01-05T16:21:55.704Z" Destination="https://werain.me/" xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"><Issuer xmlns="urn:oasis:names:tc:SAML:2.0:assertion">urn:federation:MicrosoftOnline</Issuer><NameID Format="urn:oasis:names:tc:SAML:2.0:nameid-format:persistent" xmlns="urn:oasis:names:tc:SAML:2.0:assertion">4948f6ce-4e3b-4538-b284-1461f9379b48</NameID><samlp:SessionIndex>_eafbb730-b590-0134-a918-00d202739c81</samlp:SessionIndex></samlp:LogoutRequest>
Any help here.
A SAML authentication message is a XML document with an embedded (enveloped) XMLDSig signature or a deflated encoding signature
Enveloped XMLDSign signature
<samlp:LogoutRequest>
<...saml message...>
<ds:Signature>
<ds:SignedInfo />
<ds:SignatureValue />
<ds:KeyInfo />
</ds:Signature>
</samlp:LogoutRequest>
<ds:SignatureValue> contains the signature, <ds:SignedInfo> the signed data and a reference to the message and <ds:KeyInfo> usually contains the X509Certificate with the identity of the signer, or a reference to that certicate
Deflated encoding in URL
SAMLRequest=value&RelayState=value&SigAlg=value&Signature=value
Where each value is url encoded
SAMLRequest=urlencode(base64(<samlp:LogoutRequest> <...saml message...> </samlp:LogoutRequest>))
And the signature is done on a concatenation of query string algorithm using the algorithm SigAlg
Signature = urlencode( base64 ( SigAlg ("SAMLRequest=value&RelayState=value&SigAlg=value")))
Digital signature of SAML messages
SAML message is digitally signed (not encrypted) with the private key of the issuer (SP), and can be verified with the public key of the SP. A SAML response must be signed with the private key of the identity provider (IdP), and the SP can verify the message with the public key of the IdP.
If you act as IdP and you want to verify a SAML request of the SP, you need:
Verify the digital signature: Verify using the public key of the SP that the signature match with the signed message to ensure the identity of the signer and the message has not been altered
Authorize the request: Verify that the identity of the signer can perform the requested operation. Usually you have to match the serial number or the subject of the certificate with a pre-existent list, or verify that the certificate has been issued by a trusted certificate authority
Generate the SAML response: Generate a XML message with the SAML data and sign it with your private key to send to SP
Most programming languages support XMLDsig signatures but in your case is used the deflated encoding that is a specific characteristic of SAML binding, so if your SAML library does not support it, you have to verify the signature manually. These are more or less the steps to follow according to specification
//get params from query string
String samlrequest = getQueryParam("SAMLRequest");
String relaystate = getQueryParam("RelayState");
String sigalg = getQueryParam("SigAlg");
String signature = getQueryParam("Signature");
//The signature
byte signature[] = URLDecoder.decode(Base64.getDecoder().decode(signature ), "UTF-8");
//The signed data. build the following string checking if RelayState is null
//SAMLRequest=samlrequest&RelayState=relaystate&SigAlg=sigalg
byte signedData[] = concat(samlrequest,relaystate,sigalg);
//The signature algorithm could be "SHA1WithRSA" or "SHA1withDSA" depending on sigalg is http://www.w3.org/2000/09/xmldsig#rsa-sha1 or http://www.w3.org/2000/09/xmldsig#dsa-sha1
String signatureAlgorithm = extractSignatureAlgorithm(sigalg);
//get the public key of the SP. It must be registered before this process
PublicKey publicKey = ...
//Verify the signature
Signature sig = Signature.getInstance(signatureAlgorithm);
sig.initVerify(publicKey);
sig.update(signedData);
boolean verifies = sig.verify(signature);
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