generateSasUrl and defaultAzureCredential

[asbol-leo]

generateSasUrl and defaultAzureCredential

Is your feature request related to a problem? Please describe.
I would like to be able to use the generateSasUrl method with the BlobClinet authinticated with DefaultAzureCredential to generate a SAS URL for a blob. So i can use managed identity to generate SAS URL an keeping a clean codebase.

Describe the solution you'd like
I would like that I can call the generateSasUrl method on a BlobClinet that is authinticated with DefaultAzureCredential.

This could be implemeted by either by passing an optional UserDelegationKey to the generateSasUrl method:

  public generateSasUrl(options: BlobGenerateSasUrlOptions, userDelegationKey: UserDelegationKey): Promise<string> {
    return new Promise((resolve) => {
        if (this.credential instanceof DefaultAzureCredential) {
            const sas = generateBlobSASQueryParameters(
            {
                containerName: this._containerName,
                blobName: this._name,
                snapshotTime: this._snapshot,
                versionId: this._versionId,
                ...options,
            },
            userDelegationKey,
            this.accountName
            ).toString();
            resolve(appendToURLQuery(this.url, sas));
        }

      if (!(this.credential instanceof StorageSharedKeyCredential)) {
        throw new RangeError(
          "Can only generate the SAS when the client is initialized with a shared key credential",
        );
      }

      const sas = generateBlobSASQueryParameters(
        {
          containerName: this._containerName,
          blobName: this._name,
          snapshotTime: this._snapshot,
          versionId: this._versionId,
          ...options,
        },
        this.credential,
      ).toString();

      resolve(appendToURLQuery(this.url, sas));
    });
  }

Or by using the DefaultAzureCredential to make a BlobServiceClient and then get a UserDelegationKey within the generateSasUrl method:

  public generateSasUrl(options: BlobGenerateSasUrlOptions): Promise<string> {
    return new Promise((resolve) => {
        if (this.credential instanceof DefaultAzureCredential) {
            const blobServiceClient = new BlobServiceClient(`https://${this.accountName}.blob.core.windows.net/`, this.credential);
            const userDelegationKey = blobServiceClient.getUserDelegationKey(options.startsOn, options.expiresOn);
            const sas = generateBlobSASQueryParameters(
            {
                containerName: this._containerName,
                blobName: this._name,
                snapshotTime: this._snapshot,
                versionId: this._versionId,
                ...options,
            },
            userDelegationKey,
            this.accountName
            ).toString();
            resolve(appendToURLQuery(this.url, sas));
        }

      if (!(this.credential instanceof StorageSharedKeyCredential)) {
        throw new RangeError(
          "Can only generate the SAS when the client is initialized with a shared key credential",
        );
      }

      const sas = generateBlobSASQueryParameters(
        {
          containerName: this._containerName,
          blobName: this._name,
          snapshotTime: this._snapshot,
          versionId: this._versionId,
          ...options,
        },
        this.credential,
      ).toString();

      resolve(appendToURLQuery(this.url, sas));
    });
  }

Describe alternatives you've considered
An other alternativ would be to generalize generateBlobSASQueryParameters to take DefaultAzureCredential as credential. However I have not looked in to implementing this.

Additional context
Na.

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @xgithubtriage.