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icrc_49_call_canister.md

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ICRC-49: Call Canister

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Summary

This Method can be used by the relying party to request calls to 3rd party canister executed by the signer using the requested identity. In order to prevent misuse of this method all icrc49_call_canister requests are subject to user approval.

Method

Name: icrc49_call_canister

Prerequisite: Granted permission scope icrc49_call_canister.

Scope (according to the ICRC-25 standard)

Scope: icrc49_call_canister

Example Permission Request

{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "icrc25_request_permissions",
    "params": {
        "version": "1",
        "scopes": [
            {
                "method": "icrc49_call_canister"
            }
        ]
    }
}

icrc25_supported_standards

An ICRC-25 compliant signer must implement the icrc25_supported_standards method which returns the list of supported standards. Any signer implementing ICRC-49 must include a record with the name field equal to "ICRC-49" in that list.

Request Params

canisterId (text): The id of the canister on which the call should be executed.

sender (text): The principal (textual representation) requested to execute the call.

method (text): The name of the call method to be executed.

arg (blob): The arguments for the call.

nonce (blob optional): Arbitrary data of length at most 32 bytes, typically randomly generated. This can be used to create distinct requests with otherwise identical fields.

Example RPC Request

{
    "id": 1,
    "jsonrpc": "2.0",
    "method": "icrc49_call_canister",
    "params": {
        "canisterId": "xhy27-fqaaa-aaaao-a2hlq-ca",
        "sender": "b7gqo-ulk5n-2kpo7-oalt7-p2kyl-o4j5l-kiuwo-eeybr-dab4l-ur6up-pqe",
        "method": "transfer",
        "arg": "RElETARte24AbAKzsNrDA2ithsqDBQFsA/vKAQKi3pTrBgHYo4yoDX0BAwEdV+ztKgq7E4l1ffuTuwEmw8AtYSjlrJ+WLO5ofQIAAMgB"
    }
}

Result

contentMap (blob): The CBOR-encoded content map of the actual request as specified here.

certificate (blob): The certificate returned by the read_state call as specified here. The value is CBOR-encoded.

Example RPC Response

{
    "id": 1,
    "jsonrpc": "2.0",
    "result": {
        "contentMap": "2dn3p2NhcmdYTkRJREwEbXtuAGwCs7DawwNorYbKgwUBbAP7ygECot6U6wYB2KOMqA19AQMBHVfs7SoKuxOJdX37k7sBJsPALWEo5ayflizuaH0CAADIAWtjYW5pc3Rlcl9pZEoAAAAAAcDR1wEBbmluZ3Jlc3NfZXhwaXJ5GxeNX/65y4YAa21ldGhvZF9uYW1laHRyYW5zZmVyZW5vbmNlUFF4+hAimFhoqkdUcIchz0xscmVxdWVzdF90eXBlZGNhbGxmc2VuZGVyWB1q63Snu+4C5/fpWFu4nq1IpZxCYDEYA8XSPqPfAg==",
        "certificate": "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"
    }
}

Message Processing

  1. The relying party sends a icrc49_call_canister request to the signer.
  2. Upon receiving the request, the signer validates whether it can process the message.
    • If the relying party has been denied the permission to invoke the method, the signer sends a response with an error back to the relying party. If the permission state is ask_on_use, the signer must prompt the user to either accept or deny this invocation. See permission states for more details.
  3. The signer tries to retrieve and verify the consent message according to the ICRC-21 specification. If the target canister does not support ICRC-21 consent messages for the given canister call, the signer may proceed in one of following ways:
    • The signer rejects the request and sends a response with the error code 2001 back to the relying party. Step 4 is skipped.
    • The signer displays a warning, tries to decode the arguments by itself and displays raw canister call details. If the arguments cannot be decoded, a strong warning must be displayed.

      Note: Signing canister calls without an ICRC-21 consent message is dangerous! Signing canister calls solely based on the decoded arguments might yield unexpected results. Strong technical knowledge is required to understand the consequences of such actions. Blind signing of canister calls (without even decoding the arguments) is not recommended and requires complete trust in the relying party.

      Singing canister calls without an ICRC-21 consent message must be disabled by default. The signer must explain the dangers to the user and ask explicitly to enable this feature.

  4. Next, the signer displays the transaction details to the user and prompts for approval:

    Note: User approval for the icrc49_call_canister method must never be skipped! The reason for this is that the canister call might not be idempotent and thus submitting a call more than once might have undesired consequences.

    • If the user approves the request:
      • The signer sends the call to the IC (in order to get certified results, all calls, including queries, should be sent as update calls), retrieves its content map and calculates a request id based on it.
        • The signer continues to call read_state for the calculated request id until the status of the call indicates that the call has been processed (succesfully or not).
          • If the status of the call is replied, rejected or done, the signer retrieves the CBOR-encoded certificate from the read_state response and sends it together with the content map in response back to the relying party.
        • If the status of the HTTP response for submitting the call to the IC is not 202 Accepted (indicating the call failed), the signer sends a response with an error back to the relying party.
    • If the user rejects the request or if the signer fails to complete the requested action for any reason, the signer sends a response with an error back to the relying party.
  5. The relying party receives a response from the signer and processes it as follows:
    • On successful response: the relying party verifies whether the call performed by the signer was genuine and retrieves the result:
      • The relying party retrieves the CBOR-encoded contentMap from the response, verifies that its values match the expectations and uses it to calculate a request id.
      • The relying party retrieves the CBOR-encoded certificate from the response, decodes it and validates its authenticity with regard to the root of trust.
        • If the validation process fails, the relying party rejects the response.
      • The relying party extracts the request status from the certificate's state tree.
      • If the status of the call is replied:
        • The relying party retrieves the reply blob from the certificate's state tree.
        • If the reply blob or the error information (comprised of the reject_code, reject_message) is not present, the relying party rejects the response.
      • If the status of the call is rejected:
        • The relying party uses the calculated request id to retrieve reject_code, reject_message from the certificate's state tree.
        • If the error information (comprised of the reject_code, reject_message) is not present, the relying party rejects the response.
      • If the status of the call is done:
        • The relying party now knows that the call was submitted to the IC and executed as requested. However, the result of the call is no longer available.
    • On error: The relying party may use the information returned to help investigate the causes for the error. The error information is only informative. The relying party must not trust the information returned by the signer and should not use it to make any decisions.
sequenceDiagram
    participant RP as Relying Party
    participant S as Signer
    participant U as User
    participant C as Target Canister

    RP ->> S: Request canister call
    alt Relying party has not been granted the `icrc49_call_canister` permission scope<br>or the request does not comply with scope restrictions
        S ->> RP: Error response: Permission not granted (3000)
    else
        alt Canister supports ICRC-21
            Note over S,C: Follow the ICRC-21 standard
        else Canister does not support ICRC-21 and signer does not support blind signing
            S ->> RP: Error response: No consent message (2001)
            Note over RP,S: Abort interaction, do not proceed further.
        else Canister does not support ICRC-21 and signer supports blind signing
            S ->> U: Display warning and canister call details (canisterId, sender, method, arg)
            Note over S,U: The warning must inform the user that the canister does not support ICRC-21<br/>The arguments should be decoded, otherwise a stronger warning must be displayed
        end
        alt Approved
            U ->> S: Approve request
            S ->> C: Submit canister call
            S ->> S: Wait for the canister call result
            alt Call successful
                S ->> U: Display success message
                S ->> RP: Canister call response
                RP ->> RP: Validate the certificate
                RP ->> RP: Retrieve the result
            else Call failed
                S ->> U: Display failure message
                S ->> RP: Error response: Network error (4000) | Generic error (1000)
            end
        else Rejected
            U ->> S: Reject request
            S ->> RP: Error response: Action aborted (3001)
        end
    end
Loading

Errors

See ICRC-25 for a list of errors that can be returned by all methods.

This standard defines the following additional errors:

Code Message Meaning Data
2001 No consent message The signer has rejected the request because the target canister does not support ICRC-21 consent messages for the given call N/A