[#334] Add auth doc

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

docs/authentication.md

@@ -0,0 +1,313 @@
+# Authentication and authorization scheme
+
+This document describes s3-gw authentication and authorization mechanism.
+
+## General overview
+
+Basic provisions:
+
+* A request to s3-gw can be signed or not (request that isn't signed we will cal anonymous or just anon)
+* To manage resources (buckets/objects) using s3-gw you must have appropriate access rights
+
+Each request must be authenticated (at least as anonymous) and authorized. The following scheme shows components that
+are involved to this
+process.
+
+<a>
+    <img src="images/authentication/auth-overview.svg" alt="Auth general overview"/>
+</a>
+
+There are several participants of this process:
+
+1. User that make a request
+2. S3-GW that accepts a request
+3. FrostFS Storage that stores AccessObjects (objects are needed for authentication)
+4. Blockchain smart contracts (`frostfsid`, `policy`) that stores user info and access rules.
+
+## Data auth process
+
+Let's look at the process in more detail:
+
+<a>
+    <img src="images/authentication/auth-sequence.svg" alt="Auth sequence diagram"/>
+</a>
+
+* First of all, someone make a request. If request is signed we will check its signature (`Authentication`) after that
+  we will check access rights using policies (`Auhorization`). For anonymous requests only authorization be performed.
+
+* **Authentication steps**:
+    * Each signed request is provided with `AccessKeyId` and signature. So if request is signed we must check its
+      signature. To do this we must know the `AccessKeyId`/`SecretAccessKey` pair (How the signature is calculated
+      using this pair see [signing](#aws-signing). Client and server (s3-gw) use the same credentials and algorithm to
+      compute signature). The `AccessKeyId` is a public part of credentials, and it's passed to gate in request. The
+      private part of credentials is `SecretAccessKey` and it's encrypted and stored in [AccessBox](#accessbox). So on
+      this step we must find appropriate `AccessBox` in FrostFS storage node (How to find appropriate `AccessBox`
+      knowing `AccessKeyId` see [search algorithm](#search-algorithm)). On this stage we can get `AccessDenied` from
+      FrostFS storage node if the s3-gw doesn't have permission to read this `AccessBox` object.
+
+    * After successful retrieving object we must extract `SecretAccessKey` from it. Since it's encrypted the s3-gw must
+      decrypt (see [encryption](#encryption)) this object using own private key and `SeedKey` from `AccessBox`
+      (see [AccessBox inner structure](#accessbox)). After s3-gw have got the `AccessKeyId`/`SecretAccessKey` pair it
+      [calculate signature](#aws-signing) and compare got signature with provided withing request. If signature doesn't
+      match the `AccessDenied` is returned.
+
+    * `AccessBox` also contains `OwnerID` that is related to `AccessKeyId` that was provided. So we have to check if
+      such `OwnerID` exists in `frsotfsid` contract (that stores all registered valid users). If user doesn't exist in
+      contract the `AccessDenied` is returned.
+
+* **Authorization steps**:
+    * To know if user has access right to do what he wants to do we must find appropriate access policies. Such policies
+      are stored in `policy` contract and locally (can be manged using [control api](#control-auth-process)). So we need
+      to get policies from contract and [check them](#policies) along with local to decide if user has access right. If
+      he doesn't have such right the `AccessDenied` is returned.
+
+* After successful authentication and authorization the request will be processed by s3-gw business logic and finally be
+  propagated to FrostFS storage node which also performs some auth checks and can return `AccessDenied`. If this happens
+  s3-gw also returns `AccessDenied` as response.
+
+### AWS Signing
+
+Every interaction with FrostFS S3 gateway is either authenticated or anonymous. This section explains request
+authentication with the AWS Signature Version 4 algorithm. More info in AWS documentation:
+
+* [Authenticating Requests (AWS Signature Version 4)](https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html)
+* [Signing AWS API requests](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_aws-signing.html)
+
+#### Authentication Methods
+
+You can express authentication information by using one of the following methods:
+
+* **HTTP Authorization header** - Using the HTTP Authorization header is the most common method of authenticating an
+  FrostFS S3 request. All the FrostFS S3 REST operations (except for browser-based uploads using POST requests) require
+  this header. For more information about the Authorization header value, and how to calculate signature and related
+  options,
+  see [Authenticating Requests: Using the Authorization Header (AWS Signature Version 4)](https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-auth-using-authorization-header.html).
+* **Query string parameters** - You can use a query string to express a request entirely in a URL. In this case, you use
+  query parameters to provide request information, including the authentication information. Because the request
+  signature is part of the URL, this type of URL is often referred to as a presigned URL. You can use presigned URLs to
+  embed clickable links, which can be valid for up to seven days, in HTML. For more information,
+  see [Authenticating Requests: Using Query Parameters (AWS Signature Version 4)](https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html).
+
+FrostFS S3 also supports browser-based uploads that use HTTP POST requests. With an HTTP POST request, you can upload
+content to FrostFS S3 directly from the browser. For information about authenticating POST requests,
+see [Browser-Based Uploads Using POST (AWS Signature Version 4)](https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-UsingHTTPPOST.html).
+
+#### Introduction to Signing Requests
+
+Authentication information that you send in a request must include a signature. To calculate a signature, you first
+concatenate select request elements to form a string, referred to as the string to sign. You then use a signing key to
+calculate the hash-based message authentication code (HMAC) of the string to sign.
+
+In AWS Signature Version 4, you don't use your secret access key to sign the request. Instead, you first use your secret
+access key to derive a signing key. The derived signing key is specific to the date, service, and Region. For more
+information about how to derive a signing key in different programming languages, see Examples of how to derive a
+signing key for Signature Version 4.
+
+The following diagram illustrates the general process of computing a signature.
+
+<a>
+    <img src="images/authentication/aws-signing.png" alt="AWS Signing"/>
+</a>
+
+The string to sign depends on the request type. For example, when you use the HTTP Authorization header or the query
+parameters for authentication, you use a varying combination of request elements to create the string to sign. For an
+HTTP POST request, the POST policy in the request is the string you sign. For more information about computing string to
+sign, follow links provided at the end of this section.
+
+For signing key, the diagram shows series of calculations, where result of each step you feed into the next step. The
+final step is the signing key.
+
+Upon receiving an authenticated request, FrostFS S3 servers re-create the signature by using the authentication
+information that is contained in the request. If the signatures match, FrostFS S3 processes your request; otherwise, the
+request is rejected.
+
+##### Signature Calculations for the Authorization Header
+
+To calculate a signature, you first need a string to sign. You then calculate a HMAC-SHA256 hash of the string to sign
+by using a signing key. The following diagram illustrates the process, including the various components of the string
+that you create for signing.
+
+When FrostFS S3 receives an authenticated request, it computes the signature and then compares it with the signature
+that you provided in the request. For that reason, you must compute the signature by using the same method that is used
+by FrostFS S3. The process of putting a request in an agreed-upon form for signing is called canonicalization.
+
+<a>
+    <img src="images/authentication/auth-header-signing.png" alt="Signature Calculations for the Authorization Header"/>
+</a>
+
+See detains in [AWS documentation](https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html).
+
+#### s3-gw
+
+s3-gw support the following ways to provide the singed request:
+
+* [HTTP Authorization header](https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-auth-using-authorization-header.html)
+* [Query string parameters](https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html)
+* [Browser-Based Uploads Using POST](https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-UsingHTTPPOST.html)
+
+All these methods provide `AccessKeyId` and signature. Using `AccessKeyId` s3-gw can get `SecretAccessKey`
+(see [data auth](#data-auth-process)) to compute signature using exactly the same mechanics
+as [client does](#introduction-to-signing-requests). After signature calculation the s3-gw just compares signatures and
+if they don't match the access denied is returned.
+
+### AccessBox
+
+`AccessBox` is an ordinary object in FrostFS storage. It contains all information that can be used by s3-gw to
+successfully authenticate request. Also, it contains data that is required to successful authentication in FrostFS
+storage node.
+
+Based on this object s3 credentials are formed:
+
+* `AccessKeyId` - is concatenated container id and object id (`<cid>0<oid>`) of `AccessBox` (
+  e.g. `2XGRML5EW3LMHdf64W2DkBy1Nkuu4y4wGhUj44QjbXBi05ZNvs8WVwy1XTmSEkcVkydPKzCgtmR7U3zyLYTj3Snxf`)
+* `SecretAccessKey` - hex-encoded random generated 32 bytes (that is encrypted and stored in object payload)
+
+> **Note**: sensitive info in `AccessBox` is [encrypted](#encryption), so only someone who posses specific private key
+> can decrypt such info.
+
+`AccessBox` has the following structure:
+
+<a>
+    <img src="images/authentication/accessbox-object.svg" alt="AccessBox object structure"/>
+</a>
+
+**Headers:**
+
+`AccessBox` object has the following attributes (at least them, it also can contain custom one):
+
+* `Timestamp` - unix timestamp when object was created
+* `__SYSTEM__EXPIRATION_EPOCH` - epoch after which the object isn't available anymore
+* `S3-CRDT-Versions-Add` - comma separated list of previous versions of `AccessBox` (
+  see [AccessBox versions](#accessbox-versions))
+* `S3-Access-Box-CRDT-Name` - `AccessKeyId` of credentials to which current `AccessBox` is related (
+  see [AccessBox versions](#accessbox-versions))
+* `FilePath` - just object name
+
+**Payload:**
+
+The `AccessBox` payload is an encoded [AccessBox protobuf type](../creds/accessbox/accessbox.proto) .
+It contains:
+
+* Seed key - hex-encoded public seed key to compute shared secret using ECDH (see [encryption](#encryption))
+* List of gate data:
+    * Gate public key (so that gate (when it will decrypt data later) know which one item from list it should process)
+    * Encrypted tokens:
+        * `SecretAccessKey` - hex-encoded random generated 32 bytes
+        * Marshaled bearer token - more detail
+          in [spec](https://git.frostfs.info/TrueCloudLab/frostfs-api/src/commit/4c68d92468503b10282c8a92af83a56f170c8a3a/acl/types.proto#L189)
+        * Marshaled session token - more detail
+          in [spec](https://git.frostfs.info/TrueCloudLab/frostfs-api/src/commit/4c68d92468503b10282c8a92af83a56f170c8a3a/session/types.proto#L89)
+* Container placement policies:
+    * `LocationsConstraint` - name of location constraint that can be used to create bucket/container using s3
+      credentials related to this `AccessBox`
+    * Marshaled placement policy - more detail
+      in [spec](https://git.frostfs.info/TrueCloudLab/frostfs-api/src/commit/4c68d92468503b10282c8a92af83a56f170c8a3a/netmap/types.proto#L111)
+
+#### AccessBox versions
+
+Imagine the following scenario:
+
+* There is a system where only one s3-gw exist
+* There is a `AccessBox` that can be used by this s3-gw
+* User has s3 credentials (`AccessKeyId`/`SecretAccessKey`) related to corresponded `AccessBox` and can successfully
+  make request to s3-gw
+* The system is expanded and new one s3-gw is added
+* User must be able to use the credentials (that he has already had) to make request to new one s3-gw
+
+Since `AccessBox` object is immutable and `SecretAccessKey` is encrypted only for restricted list of keys (can be used
+(decrypted) only by limited number of s3-gw) we have to create new `AccessBox` that has encrypted secrets for new list
+of s3-gw and be related to initial s3 credentials (`AccessKeyId`/`SecretAccessKey`). Such relationship is done
+by `S3-Access-Box-CRDT-Name`.
+
+##### Search algorithm
+
+To support scenario from previous section and find appropriate version of `AccessBox` (that contains more recent and
+relevant data) the following sequence is used:
+
+<a>
+    <img src="images/authentication/accessbox-search.svg" alt="AccessBox search process"/>
+</a>
+
+* Search all object whose attribute `S3-Access-Box-CRDT-Name` is equal to `AccessKeyId` (extract container id
+  from `AccessKeyId` that has format: `<cid>0<oid>`).
+* Get metadata for these object using `HEAD` requests (not `Get` to reduce network traffic)
+* Sort all these objects by creation epoch and object id
+* Pick last object id (If no object is found then extract object id from `AccessKeyId` that has format: `<cid>0<oid>`.
+  We need to do this because versions of `AccessBox` can miss the `S3-Access-Box-CRDT-Name` attribute.)
+* Get appropriate object from FrostFS storage
+* Decrypt `AccessBox` (see [encryption](#encryption))
+
+#### Encryption
+
+Each `AccessBox` contains sensitive information (`AccessSecretKey`, bearer/session tokens etc.) that must be protected
+and available only to trusted parties (in our case it's a s3-gw).
+
+To encrypt/decrypt data the authenticated encryption with associated
+data ([AEAD](https://en.wikipedia.org/wiki/Authenticated_encryption)) is used. The encryption algorithm
+is [ChaCha20-Poly1305](https://en.wikipedia.org/wiki/ChaCha20-Poly1305) ([RFC](https://datatracker.ietf.org/doc/html/rfc7905)).
+
+Is the following algorithm the ECDSA keys (with curve implements NIST P-256 (FIPS 186-3, section D.2.3) also known as
+secp256r1 or prime256v1) is used (unless otherwise stated).
+
+**Encryption:**
+
+* Create ephemeral key (`SeedKey`), it's need to generate shared secret
+* Generate random 32-byte (that after hex-encoded be `SecretAccessKey`) or use existing secret access key
+  (if `AccessBox` is being updated rather than creating brand new)
+* Generate shared secret as [ECDH](https://en.wikipedia.org/wiki/Elliptic-curve_Diffie%E2%80%93Hellman)
+* Derive 32-byte key using shared secret from previous step with key derivation function based on
+  HMAC with SHA256 [HKDF](https://en.wikipedia.org/wiki/HKDF)
+* Encrypt marshaled [Tokens](../creds/accessbox) using derived key
+  with [ChaCha20-Poly1305](https://en.wikipedia.org/wiki/ChaCha20-Poly1305) algorithm without additional data.
+
+**Decryption:**
+
+* Get public part of `SeedKey` from `AccessBox`
+* Generate shared secret as follows:
+    * Make scalar curve multiplication of public part of `SeedKey` and private part of s3-gw key
+    * Use `X` part of multiplication (with zero padding at the beginning to fit 32-byte)
+* Derive 32-byte key using shared secret from previous step with key derivation function based on
+  HMAC with SHA256 [HKDF](https://en.wikipedia.org/wiki/HKDF)
+* Decrypt encrypted marshaled [Tokens](../creds/accessbox) using derived key
+  with [ChaCha20-Poly1305](https://en.wikipedia.org/wiki/ChaCha20-Poly1305) algorithm without additional data.
+
+### Policies
+
+The main repository that contains policy implementation is https://git.frostfs.info/TrueCloudLab/policy-engine.
+
+Policies can be stored locally (using [control api](#control-auth-process)) or in `policy` contract. When policies check
+is performed the following algorithm is applied:
+
+* Check local policies:
+    * If any rule was matched return checking result.
+* Check contract policies:
+    * If any rule was matched return checking result.
+    * If no rules were matched return `deny` status.
+
+To local and contract policies `deny first` scheme is applied. This means that if several rules were matched for
+reqeust (with both statuses `allow` and `deny`) the resulting status be `deny`.
+
+Policy rules validate if specified request can be performed on the specific resource. Request and resource can contain
+some properties and rules can contain conditions on some such properties.
+
+In s3-gw resource is `/bucket/object`, `/bucket` or just `/` (if request is trying to list buckets).
+Currently, request that is checked contains the following properties (so policy rule can contain conditions on them):
+
+* `Owner` - address of owner that is performing request (this is taken from bearer token from `AccessBox`)
+* `frostfsid:groupID` - groups to which the owner belongs (this is taken from `frostfsid` contract)
+
+## Control auth process
+
+There are control path [grpc api](../pkg/service/control/service.proto) in s3-gw that also has their own authentication
+and authorization process.
+
+But this process is quite straight forward:
+
+* Get grpc request
+* Check if signing key belongs to [allowed key list](configuration.md#control-section) (that is located in config file)
+* Validate signature
+
+For signing process the asymmetric encryption based on elliptic curves (`ECDSA_SHA512`) is used.
+For more details see the appropriate code
+in [frostfs-api](https://git.frostfs.info/TrueCloudLab/frostfs-api/src/commit/4c68d92468503b10282c8a92af83a56f170c8a3a/refs/types.proto#L94)
+and [frostfs-api-go](https://git.frostfs.info/TrueCloudLab/frostfs-api-go/src/commit/a85146250b312fcdd6da9a71285527fed544234f/refs/types.go#L38).

docs/images/authentication/accessbox-object.puml

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+@startuml
+
+package AccessBox {
+  map Tokens {
+    SecretKey => Private key
+    BearerToken => Encoded bearer token
+    SessionTokens => List of encoded session tokens
+  }
+
+  map Gate {
+    GateKey => Encoded public gate key
+    Encrypted tokens *--> Tokens
+  }
+
+  map ContainerPolicy {
+    LocationConstraint => Policy name
+    PlacementPolicy => Encoded placement policy
+  }
+
+  map Box {
+    SeedKey => Encoded public seed key
+    List of Gates *--> Gate
+    List of container policies *--> ContainerPolicy
+  }
+
+
+  map ObjectAttributes {
+    Timestamp => 1710418478
+    _~_SYSTEM_~_EXPIRATION_EPOCH => 10801
+    S3-CRDT-Versions-Add => 5ZNvs8WVwy1XTmSEkcVkydPKzCgtmR7U3zyLYTj3Snxf,9bLtL1EsUpuSiqmHnqFf6RuT6x5QMLMNBqx7vCcCcNhy
+    S3-Access-Box-CRDT-Name => 2XGRML5EW3LMHdf64W2DkBy1Nkuu4y4wGhUj44QjbXBi05ZNvs8WVwy1XTmSEkcVkydPKzCgtmR7U3zyLYTj3Snxf
+    FilePath => 1710418478_access.box
+  }
+
+  map FrostFSObject {
+    Header *-> ObjectAttributes
+    Payload *--> Box
+  }
+
+
+}
+
+
+@enduml

docs/images/authentication/accessbox-search.puml

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+@startuml
+
+User -> "S3-GW": AccessKey
+"S3-GW" -> "FrostFS Node": Search objects
+
+note right
+Search by exact attribute matching:
+**S3-Access-Box-CRDT-Name:** //AccessKey//
+end note
+
+"FrostFS Node" --> "S3-GW": AccessBox objects ids
+
+"S3-GW" -> "FrostFS Node" : Head AccessBox objects
+"FrostFS Node" --> "S3-GW": AccessBox object headers
+
+"S3-GW" -> "S3-GW": Choose latest AccessBox
+
+note left
+Sort AccessBox headers by creation epoch
+and then by ObjectID
+Pick last
+end note
+
+"S3-GW" -> "FrostFS Node" : Get AccessBox object
+"FrostFS Node" --> "S3-GW": AccessBox object
+
+"S3-GW" -> "S3-GW": Decrypt and validate AccessBox
+
+@enduml

docs/images/authentication/auth-overview.puml

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+@startuml
+!include <c4/C4_Container.puml>
+AddElementTag("smart-contract", $bgColor=#0abab5)
+
+Person(user, "User", "User with or without credentials")
+
+System_Boundary(c1, "FrostFS") {
+    Container(s3, "S3 Gateway", $descr="AWS S3 compatible gate")
+    Container(stor, "FrostFS Storage", $descr="Storage service")
+}
+
+System_Boundary(c3, "Blockchain") {
+    Interface "NeoGo"
+    Container(ffsid, "FrostFS ID", $tags="smart-contract", $descr="Stores namespaces and users")
+    Container(policy, "Policy", $tags="smart-contract", $descr="Stores APE rules")
+}
+
+Rel_R(user, s3, "Requests", "HTTP")
+Rel_R(s3, stor, "Get data to validate request, store objects")
+Rel_D(s3, NeoGo, "Get data to validate request")
+Rel("NeoGo",  ffsid, "Fetch users")
+Rel("NeoGo",  policy, "Fetch policies")
+
+SHOW_LEGEND(true)
+@enduml

docs/images/authentication/auth-overview.svg

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+entity s3--><g id="elem_s3"><rect fill="#438DD5" height="85.1875" rx="2.5" ry="2.5" style="stroke:#3C7FC0;stroke-width:0.5;" width="199" x="274.5" y="58"/><text fill="#FFFFFF" font-family="sans-serif" font-size="16" font-weight="bold" lengthAdjust="spacing" textLength="108" x="320" y="82.8516">S3 Gateway</text><text fill="#FFFFFF" font-family="sans-serif" font-size="12" font-style="italic" lengthAdjust="spacing" textLength="10" x="369" y="97.7637">[]</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="372" y="113.5889"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="175" x="288.5" y="129.8857">AWS S3 compatible gate</text></g><!--MD5=[b631bc93683c8d3c6bcd86869bd62c2d]
+entity stor--><g id="elem_stor"><rect fill="#438DD5" height="85.1875" rx="2.5" ry="2.5" style="stroke:#3C7FC0;stroke-width:0.5;" width="169" x="660.5" y="58"/><text fill="#FFFFFF" font-family="sans-serif" font-size="16" font-weight="bold" lengthAdjust="spacing" textLength="149" x="670.5" y="82.8516">FrostFS Storage</text><text fill="#FFFFFF" font-family="sans-serif" font-size="12" font-style="italic" lengthAdjust="spacing" textLength="10" x="740" y="97.7637">[]</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="743" y="113.5889"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="111" x="691.5" y="129.8857">Storage service</text></g><!--MD5=[d75780de534459f9083ff96c63e26824]
+entity NeoGo--><g id="elem_NeoGo"><ellipse cx="374" cy="323.5" fill="#F1F1F1" rx="8" ry="8" style="stroke:#181818;stroke-width:0.5;"/><text fill="#000000" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="48" x="350" y="353.4951">NeoGo</text></g><!--MD5=[a1c7fbed12783ec305c3357d72c64f9e]
+entity ffsid--><g id="elem_ffsid"><rect fill="#0ABAB5" height="101.4844" rx="2.5" ry="2.5" style="stroke:#3C7FC0;stroke-width:0.5;" width="198" x="275" y="427.5"/><text fill="#FFFFFF" font-family="sans-serif" font-size="16" font-weight="bold" lengthAdjust="spacing" textLength="96" x="326" y="452.3516">FrostFS ID</text><text fill="#FFFFFF" font-family="sans-serif" font-size="12" font-style="italic" lengthAdjust="spacing" textLength="10" x="369" y="467.2637">[]</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="372" y="483.0889"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="170" x="289" y="499.3857">Stores namespaces and</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="38" x="355" y="515.6826">users</text></g><!--MD5=[4361443624774238dacd0e01c3165ecf]
+entity policy--><g id="elem_policy"><rect fill="#0ABAB5" height="85.1875" rx="2.5" ry="2.5" style="stroke:#3C7FC0;stroke-width:0.5;" width="139" x="508.5" y="435.5"/><text fill="#FFFFFF" font-family="sans-serif" font-size="16" font-weight="bold" lengthAdjust="spacing" textLength="52" x="552" y="460.3516">Policy</text><text fill="#FFFFFF" font-family="sans-serif" font-size="12" font-style="italic" lengthAdjust="spacing" textLength="10" x="573" y="475.2637">[]</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="576" y="491.0889"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="115" x="522.5" y="507.3857">Stores APE rules</text></g><!--MD5=[8fc3522a43f8c7199df5e09e5bb0188e]
+entity user--><g id="elem_user"><rect fill="#08427B" height="135.5156" rx="2.5" ry="2.5" style="stroke:#073B6F;stroke-width:0.5;" width="168" x="7" y="32.5"/><image height="48" width="48" x="67" xlink:href="data:image/png;base64,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" y="42.5"/><text fill="#FFFFFF" font-family="sans-serif" font-size="16" font-weight="bold" lengthAdjust="spacing" textLength="42" x="70" y="105.3516">User</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="89" y="122.1201"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="140" x="21" y="138.417">User with or without</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="79" x="51.5" y="154.7139">credentials</text></g><!--MD5=[52d0c115c7d06b979b7f69659773ccc0]
+link user to s3--><g id="link_user_s3"><path d="M175.14,100.5 C203.78,100.5 236.2,100.5 266.42,100.5 " fill="none" id="user-to-s3" style="stroke:#666666;stroke-width:1.0;"/><polygon fill="#666666" points="274.47,100.5,266.47,97.5,266.47,103.5,274.47,100.5" style="stroke:#666666;stroke-width:1.0;"/><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="63" x="193.25" y="80.6387">Requests</text><text fill="#666666" font-family="sans-serif" font-size="12" font-style="italic" lengthAdjust="spacing" textLength="40" x="204.75" y="94.6074">[HTTP]</text></g><!--MD5=[22d466a8c2458259cbad703a0636b8fb]
+link s3 to stor--><g id="link_s3_stor"><path d="M473.91,100.5 C529.33,100.5 597.81,100.5 652.08,100.5 " fill="none" id="s3-to-stor" style="stroke:#666666;stroke-width:1.0;"/><polygon fill="#666666" points="660.32,100.5,652.32,97.5,652.32,103.5,660.32,100.5" style="stroke:#666666;stroke-width:1.0;"/><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="136" x="497" y="80.6387">Get data to validate</text><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="150" x="492" y="94.6074">request, store objects</text></g><!--MD5=[8c98dd26c815ae7a8024bcc2d9dd4f66]
+link s3 to NeoGo--><g id="link_s3_NeoGo"><path d="M374,143.07 C374,192.21 374,271.65 374,305.9 " fill="none" id="s3-to-NeoGo" style="stroke:#666666;stroke-width:1.0;"/><polygon fill="#666666" points="374,314.3,377,306.3,371,306.3,374,314.3" style="stroke:#666666;stroke-width:1.0;"/><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="136" x="375" y="210.6387">Get data to validate</text><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="53" x="418.5" y="224.6074">request</text></g><!--MD5=[67f0c0ebd6d2a23c30e202ac0cd81435]
+link NeoGo to ffsid--><g id="link_NeoGo_ffsid"><path d="M374,332.7 C374,348.95 374,386.52 374,419.25 " fill="none" id="NeoGo-to-ffsid" style="stroke:#666666;stroke-width:1.0;"/><polygon fill="#666666" points="374,427.45,377,419.45,371,419.45,374,427.45" style="stroke:#666666;stroke-width:1.0;"/><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="79" x="375" y="394.6387">Fetch users</text></g><!--MD5=[d37da9b99a3aca6bfa9447725e2e6374]
+link NeoGo to policy--><g id="link_NeoGo_policy"><path d="M383.06,329.95 C399.4,339.87 434.74,361.78 463,382.5 C483.22,397.33 504.63,414.49 523.43,430.09 " fill="none" id="NeoGo-to-policy" style="stroke:#666666;stroke-width:1.0;"/><polygon fill="#666666" points="529.7,435.31,525.4816,427.88,521.6363,432.4858,529.7,435.31" style="stroke:#666666;stroke-width:1.0;"/><text fill="#666666" font-family="sans-serif" font-size="12" font-weight="bold" lengthAdjust="spacing" textLength="93" x="483" y="394.6387">Fetch policies</text></g><rect fill="none" height="16.2969" style="stroke:none;stroke-width:1.0;" width="236" x="584" y="568.5"/><text fill="#000000" font-family="sans-serif" font-size="14" font-weight="bold" lengthAdjust="spacing" textLength="59" x="584" y="581.4951">Legend</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="643" y="581.4951"> </text><rect fill="#08427B" height="16.2969" style="stroke:none;stroke-width:1.0;" width="236" x="584" y="584.7969"/><text fill="#073B6F" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="8" x="588" y="597.792">▯</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="596" y="597.792"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="49" x="604" y="597.792">person</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="657" y="597.792"> </text><rect fill="#438DD5" height="16.2969" style="stroke:none;stroke-width:1.0;" width="236" x="584" y="601.0938"/><text fill="#3C7FC0" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="8" x="588" y="614.0889">▯</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="596" y="614.0889"> </text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="68" x="604" y="614.0889">container</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="676" y="614.0889"> </text><rect fill="#0ABAB5" height="16.2969" style="stroke:none;stroke-width:1.0;" width="236" x="584" y="617.3906"/><text fill="#0ABAB5" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="8" x="588" y="630.3857">▯</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="596" y="630.3857"> </text><text fill="#66622E" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="208" x="604" y="630.3857">smart-contract (no text color)</text><text fill="#FFFFFF" font-family="sans-serif" font-size="14" lengthAdjust="spacing" textLength="4" x="816" y="630.3857"> </text><line style="stroke:none;stroke-width:1.0;" x1="584" x2="820" y1="568.5" y2="568.5"/><line style="stroke:none;stroke-width:1.0;" x1="584" x2="820" y1="584.7969" y2="584.7969"/><line style="stroke:none;stroke-width:1.0;" x1="584" x2="820" y1="601.0938" y2="601.0938"/><line style="stroke:none;stroke-width:1.0;" x1="584" x2="820" y1="617.3906" y2="617.3906"/><line style="stroke:none;stroke-width:1.0;" x1="584" x2="820" y1="633.6875" y2="633.6875"/><line style="stroke:none;stroke-width:1.0;" x1="584" x2="584" y1="568.5" y2="633.6875"/><line style="stroke:none;stroke-width:1.0;" x1="820" x2="820" y1="568.5" y2="633.6875"/><!--MD5=[c02d88aa5b998c40021c1d715125d393]
+@startuml
+!include <c4/C4_Container.puml>
+AddElementTag("smart-contract", $bgColor=#0abab5)
+
+Person(user, "User", "User with or without credentials")
+
+System_Boundary(c1, "FrostFS") {
+    Container(s3, "S3 Gateway", $descr="AWS S3 compatible gate")
+    Container(stor, "FrostFS Storage", $descr="Storage service")
+}
+
+System_Boundary(c3, "Blockchain") {
+    Interface "NeoGo"
+    Container(ffsid, "FrostFS ID", $tags="smart-contract", $descr="Stores namespaces and users")
+    Container(policy, "Policy", $tags="smart-contract", $descr="Stores APE rules")
+}
+
+Rel_R(user, s3, "Requests", "HTTP")
+Rel_R(s3, stor, "Get data to validate request, store objects")
+Rel_D(s3, NeoGo, "Get data to validate request")
+Rel("NeoGo",  ffsid, "Fetch users")
+Rel("NeoGo",  policy, "Fetch policies")
+
+SHOW_LEGEND(true)
+@enduml
+
+@startuml
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+skinparam defaultTextAlignment center
+
+skinparam wrapWidth 200
+skinparam maxMessageSize 150
+
+skinparam LegendBorderColor transparent
+skinparam LegendBackgroundColor transparent
+skinparam LegendFontColor #FFFFFF
+
+skinparam shadowing<<legendArea>> false
+skinparam rectangle<<legendArea>> {
+    backgroundcolor #00000000
+    bordercolor #00000000
+}
+
+skinparam rectangle {
+    StereotypeFontSize 12
+    shadowing false
+}
+
+skinparam database {
+    StereotypeFontSize 12
+    shadowing false
+}
+
+skinparam queue {
+    StereotypeFontSize 12
+    shadowing false
+}
+
+skinparam arrow {
+    Color #666666
+    FontColor #666666
+    FontSize 12
+}
+
+skinparam actor {
+    StereotypeFontSize 12
+    shadowing false
+    style awesome
+}
+
+skinparam person {
+    StereotypeFontSize 12
+    shadowing false
+}
+
+skinparam package {
+    StereotypeFontSize 6
+    StereotypeFontColor transparent
+    FontStyle plain
+    BackgroundColor transparent
+}
+
+skinparam rectangle<<boundary>> {
+    Shadowing false
+    StereotypeFontSize 6
+    StereotypeFontColor transparent
+    FontColor #444444
+    BorderColor #444444
+    BackgroundColor transparent
+    BorderStyle dashed
+}
+
+
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+
+
+
+
+
+skinparam rectangle<<person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #08427B
+    BorderColor #073B6F
+}
+skinparam database<<person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #08427B
+    BorderColor #073B6F
+}
+skinparam queue<<person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #08427B
+    BorderColor #073B6F
+}
+skinparam actor<<person>> {
+    StereotypeFontColor #08427B
+    FontColor #08427B
+    BackgroundColor #08427B
+    BorderColor #073B6F
+}
+skinparam person<<person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #08427B
+    BorderColor #073B6F
+}
+
+
+skinparam rectangle<<external_person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #686868
+    BorderColor #8A8A8A
+}
+skinparam database<<external_person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #686868
+    BorderColor #8A8A8A
+}
+skinparam queue<<external_person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #686868
+    BorderColor #8A8A8A
+}
+skinparam actor<<external_person>> {
+    StereotypeFontColor #686868
+    FontColor #686868
+    BackgroundColor #686868
+    BorderColor #8A8A8A
+}
+skinparam person<<external_person>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #686868
+    BorderColor #8A8A8A
+}
+
+
+skinparam rectangle<<system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #1168BD
+    BorderColor #3C7FC0
+}
+skinparam database<<system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #1168BD
+    BorderColor #3C7FC0
+}
+skinparam queue<<system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #1168BD
+    BorderColor #3C7FC0
+}
+skinparam actor<<system>> {
+    StereotypeFontColor #1168BD
+    FontColor #1168BD
+    BackgroundColor #1168BD
+    BorderColor #3C7FC0
+}
+skinparam person<<system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #1168BD
+    BorderColor #3C7FC0
+}
+
+
+skinparam rectangle<<external_system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #999999
+    BorderColor #8A8A8A
+}
+skinparam database<<external_system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #999999
+    BorderColor #8A8A8A
+}
+skinparam queue<<external_system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #999999
+    BorderColor #8A8A8A
+}
+skinparam actor<<external_system>> {
+    StereotypeFontColor #999999
+    FontColor #999999
+    BackgroundColor #999999
+    BorderColor #8A8A8A
+}
+skinparam person<<external_system>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #999999
+    BorderColor #8A8A8A
+}
+
+
+
+
+
+sprite $person [48x48/16] {
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+000000BFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5000000
+000003FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD000000
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+00000DFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF600000
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+000000000000000000000000000000000000000000000000
+000000000000000000000000000000000000000000000000
+}
+
+sprite $person2 [48x48/16] {
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+000006FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE100000
+00003FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFB00000
+0000BFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF50000
+0003FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFD0000
+0009FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF2000
+000DFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF6000
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+001FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFB000
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+000DFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF6000
+0009FFFFFFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFFFFFF2000
+0003FFFFFFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFFFFFD0000
+0000BFFFFFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFFFFF50000
+00003FFFFFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFFFFB00000
+000006FFFFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFFFE100000
+0000007FFFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFFD2000000
+00000004EFFF8FFFFFFFFFFFFFFFFFFFFFF8FFFB10000000
+0000000007DF8FFFFFFFFFFFFFFFFFFFFFF8FB4000000000
+000000000002578888888888888888888864100000000000
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+skinparam rectangle<<container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #438DD5
+    BorderColor #3C7FC0
+}
+skinparam database<<container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #438DD5
+    BorderColor #3C7FC0
+}
+skinparam queue<<container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #438DD5
+    BorderColor #3C7FC0
+}
+skinparam actor<<container>> {
+    StereotypeFontColor #438DD5
+    FontColor #438DD5
+    BackgroundColor #438DD5
+    BorderColor #3C7FC0
+}
+skinparam person<<container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #438DD5
+    BorderColor #3C7FC0
+}
+
+
+skinparam rectangle<<external_container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #B3B3B3
+    BorderColor #A6A6A6
+}
+skinparam database<<external_container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #B3B3B3
+    BorderColor #A6A6A6
+}
+skinparam queue<<external_container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #B3B3B3
+    BorderColor #A6A6A6
+}
+skinparam actor<<external_container>> {
+    StereotypeFontColor #B3B3B3
+    FontColor #B3B3B3
+    BackgroundColor #B3B3B3
+    BorderColor #A6A6A6
+}
+skinparam person<<external_container>> {
+    StereotypeFontColor #FFFFFF
+    FontColor #FFFFFF
+    BackgroundColor #B3B3B3
+    BorderColor #A6A6A6
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+skinparam rectangle<<smart-contract>> {
+    BackgroundColor #0abab5
+}
+skinparam database<<smart-contract>> {
+    BackgroundColor #0abab5
+}
+skinparam queue<<smart-contract>> {
+    BackgroundColor #0abab5
+}
+skinparam actor<<smart-contract>> {
+    StereotypeFontColor #0abab5
+    FontColor #0abab5
+    BackgroundColor #0abab5
+}
+skinparam person<<smart-contract>> {
+    BackgroundColor #0abab5
+}
+
+
+
+rectangle "<$person>\n==User\n\n User with or without credentials" <<person>> as user 
+
+rectangle "==FrostFS\n<size:12>[System]</size>" <<boundary>> as c1  {
+    rectangle "==S3 Gateway\n//<size:12>[]</size>//\n\n AWS S3 compatible gate" <<container>> as s3 
+    rectangle "==FrostFS Storage\n//<size:12>[]</size>//\n\n Storage service" <<container>> as stor 
+}
+
+rectangle "==Blockchain\n<size:12>[System]</size>" <<boundary>> as c3  {
+    Interface "NeoGo"
+    rectangle "==FrostFS ID\n//<size:12>[]</size>//\n\n Stores namespaces and users" <<smart-contract>><<container>> as ffsid 
+    rectangle "==Policy\n//<size:12>[]</size>//\n\n Stores APE rules" <<smart-contract>><<container>> as policy 
+}
+
+user -RIGHT->> s3 : **Requests**\n//<size:12>[HTTP]</size>//
+s3 -RIGHT->> stor : **Get data to validate request, store objects**
+s3 -DOWN->> NeoGo : **Get data to validate request**
+NeoGo - ->> ffsid : **Fetch users**
+NeoGo - ->> policy : **Fetch policies**
+
+hide stereotype
+legend right
+<#00000000,#00000000>|<color:#000000>**Legend**</color> |
+|<#08427B><color:#073B6F> <U+25AF></color> <color:#FFFFFF> person </color> |
+|<#438DD5><color:#3C7FC0> <U+25AF></color> <color:#FFFFFF> container </color> |
+|<#0abab5><color:#0abab5> <U+25AF></color> <color:#66622E> smart-contract (no text color) </color> |
+endlegend
+@enduml
+
+PlantUML version 1.2022.13(Sat Nov 19 16:22:17 MSK 2022)
+(GPL source distribution)
+Java Runtime: OpenJDK Runtime Environment
+JVM: OpenJDK 64-Bit Server VM
+Default Encoding: UTF-8
+Language: en
+Country: US
+--></g></svg>

docs/images/authentication/auth-sequence.puml

@@ -0,0 +1,60 @@
+@startuml
+
+participant User
+participant "S3-GW"
+collections "FrostFS Storage"
+
+User -> "S3-GW": Request
+
+group signed request
+
+    "S3-GW" -> "FrostFS Storage": Find Access Box
+    "FrostFS Storage" -> "FrostFS Storage": Check request
+
+    alt #pink Check failure
+        "FrostFS Storage" -->> "S3-GW": Access Denied
+        "S3-GW" -->> User: Access Denied
+    end
+
+    "FrostFS Storage" -->> "S3-GW": Access Box
+    "S3-GW" -> "S3-GW": Check sign
+
+    alt #pink Check failure
+        "S3-GW" -->> User: Access Denied
+    end
+
+    "S3-GW" -> "frostfsid contract": Find user
+    "frostfsid contract" -->> "S3-GW": User info
+    "S3-GW" -> "S3-GW": Check user info
+
+    alt #pink Check failure
+        "S3-GW" -->> User: Access Denied
+    end
+
+end
+
+"S3-GW" -> "policy contract": Get policies
+"policy contract" -->> "S3-GW": Policies
+"S3-GW" -> "S3-GW": Check policy
+
+alt #pink Check failure
+    "S3-GW" -->> User: Access Denied
+end
+
+"S3-GW" -> "FrostFS Storage": User Request
+"FrostFS Storage" -> "FrostFS Storage": Check request
+
+alt #pink Check failure
+    "FrostFS Storage" -->> "S3-GW": Access Denied
+    "S3-GW" -->> User: Access Denied
+end
+
+"FrostFS Storage" -->> "S3-GW": Response
+"S3-GW" -->> User: Response
+
+box "Neo Go"
+    participant "frostfsid contract"
+    participant "policy contract"
+end box
+
+@enduml