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118 lines
6.0 KiB
Markdown
118 lines
6.0 KiB
Markdown
# AssumeRoleWithCertificate [](https://slack.min.io)
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## Introduction
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MinIO provides a custom STS API that allows authentication with client X.509 / TLS certificates.
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A major advantage of certificate-based authentication compared to other STS authentication methods, like OpenID Connect or LDAP/AD, is that client authentication works without any additional/external component that must be constantly available. Therefore, certificate-based authentication may provide better availability / lower operational complexity.
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The MinIO TLS STS API can be configured via MinIO's standard configuration API (i.e. using `mc admin config set/get`). Further, it can be configured via the following environment variables:
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```
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mc admin config set myminio identity_tls --env
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KEY:
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identity_tls enable X.509 TLS certificate SSO support
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ARGS:
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MINIO_IDENTITY_TLS_SKIP_VERIFY (on|off) trust client certificates without verification. Defaults to "off" (verify)
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```
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The MinIO TLS STS API is disabled by default. However, it can be *enabled* by setting environment variable:
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```
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export MINIO_IDENTITY_TLS_ENABLE=on
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```
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## Example
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MinIO exposes a custom S3 STS API endpoint as `Action=AssumeRoleWithCertificate`. A client has to send an HTTP `POST` request to `https://<host>:<port>?Action=AssumeRoleWithCertificate&Version=2011-06-15`. Since the authentication and authorization happens via X.509 certificates the client has to send the request over **TLS** and has to provide
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a client certificate.
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The following curl example shows how to authenticate to a MinIO server with client certificate and obtain STS access credentials.
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```curl
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curl -X POST --key private.key --cert public.crt "https://minio:9000?Action=AssumeRoleWithCertificate&Version=2011-06-15&DurationSeconds=3600"
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```
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<AssumeRoleWithCertificateResponse xmlns="https://sts.amazonaws.com/doc/2011-06-15/">
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<AssumeRoleWithCertificateResult>
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<Credentials>
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<AccessKeyId>YC12ZBHUVW588BQAE5BM</AccessKeyId>
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<SecretAccessKey>Zgl9+zdE0pZ88+hLqtfh0ocLN+WQTJixHouCkZkW</SecretAccessKey>
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<Expiration>2021-07-19T20:10:45Z</Expiration
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<SessionToken>eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJhY2Nlc3NLZXkiOiJZQzEyWkJIVVZXNTg4QlFBRTVCTSIsImV4cCI6MTYyNjcyNTQ0NX0.wvMUf3w_x16qpVWgua8WxnV1Sgtv1jOnSu03vbrwOMzV3cI4q3_9WZD9LwlP-34DTsvbsg7gCBGh6YNriMMiQw</SessionToken>
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</Credentials>
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</AssumeRoleWithCertificateResult>
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<ResponseMetadata>
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<RequestId>169339CD8B3A6948</RequestId>
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</ResponseMetadata>
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</AssumeRoleWithCertificateResponse>
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```
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## Authentication Flow
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A client can request temp. S3 credentials via the STS API. It can authenticate via a client certificate and obtain a access/secret key pair as well as a session token. These credentials are associated to an S3 policy at the MinIO server.
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In case of certificate-based authentication, MinIO has to map the client-provided certificate to an S3 policy. MinIO does this via the subject common name field of the X.509 certificate. So, MinIO will associate a certificate with a subject `CN = foobar` to a S3 policy named `foobar`.
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The following self-signed certificate is issued for `consoleAdmin`. So, MinIO would associate it with the pre-defined `consoleAdmin` policy.
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```
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Certificate:
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Data:
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Version: 3 (0x2)
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Serial Number:
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35:ac:60:46:ad:8d:de:18:dc:0b:f6:98:14:ee:89:e8
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Signature Algorithm: ED25519
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Issuer: CN = consoleAdmin
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Validity
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Not Before: Jul 19 15:08:44 2021 GMT
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Not After : Aug 18 15:08:44 2021 GMT
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Subject: CN = consoleAdmin
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Subject Public Key Info:
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Public Key Algorithm: ED25519
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ED25519 Public-Key:
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pub:
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5a:91:87:b8:77:fe:d4:af:d9:c7:c7:ce:55:ae:74:
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aa:f3:f1:fe:04:63:9b:cb:20:97:61:97:90:94:fa:
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12:8b
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X509v3 extensions:
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X509v3 Key Usage: critical
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Digital Signature
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X509v3 Extended Key Usage:
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TLS Web Client Authentication
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X509v3 Basic Constraints: critical
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CA:FALSE
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Signature Algorithm: ED25519
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7e:aa:be:ed:47:4d:b9:2f:fc:ed:7f:5a:fc:6b:c0:05:5b:f5:
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a0:31:fe:86:e3:8e:3f:49:af:6d:d5:ac:c7:c4:57:47:ce:97:
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7d:ab:b8:e9:75:ec:b4:39:fb:c8:cf:53:16:5b:1f:15:b6:7f:
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5a:d1:35:2d:fc:31:3a:10:e7:0c
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```
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> Observe the `Subject: CN = consoleAdmin` field.
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Also, note that the certificate has to contain the `Extended Key Usage: TLS Web Client Authentication`. Otherwise, MinIO would not accept the certificate as client certificate.
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Now, the STS certificate-based authentication happens in 4 steps:
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- Client sends HTTP `POST` request over a TLS connection hitting the MinIO TLS STS API.
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- MinIO verifies that the client certificate is valid.
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- MinIO tries to find a policy that matches the `CN` of the client certificate.
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- MinIO returns temp. S3 credentials associated to the found policy.
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The returned credentials expiry after a certain period of time that can be configured via `&DurationSeconds=3600`. By default, the STS credentials are valid for 1 hour. The minimum expiration allowed is 15 minutes.
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Further, the temp. S3 credentials will never out-live the client certificate. For example, if the `MINIO_IDENTITY_TLS_STS_EXPIRY` is 7 days but the certificate itself is only valid for the next 3 days, then MinIO will return S3 credentials that are valid for 3 days only.
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## Caveat
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*Applications that use direct S3 API will work fine, however interactive users uploading content using (when POSTing to the presigned URL an app generates) a popup becomes visible on browser to provide client certs, you would have to manually cancel and continue. This may be annoying to use but there is no workaround for now.*
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## Explore Further
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- [MinIO Admin Complete Guide](https://min.io/docs/minio/linux/reference/minio-mc-admin.html)
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- [The MinIO documentation website](https://min.io/docs/minio/linux/index.html)
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