Key must be a buffer

Start by reproducing the node-lambda deploy flow using EC2 role credentials, then trace the failure through the AWS SDK signing paths shown in the stack trace, especially util.js, v4_credentials.js, and v4.js. Determine whether role-based credentials are expected to work and define completion as either a successful deployment or a clearly documented limitation.

+ node-lambda deploy
=> Moving files to temporary directory
=> Running npm install --production
=> Zipping deployment package
=> Zipping repo. This might take up to 30 seconds
=> Reading zip file to memory
=> Reading event source file to memory
=> Uploading zip file to AWS Lambda eu-west-1 with parameters:
{ FunctionName: 'api-production',
  Code: { ZipFile: <Buffer 50 4b 03 04 14 00 08 00 08 00 48 6c fb 4a 00 00 00 00 00 00 00 00 00 00 00 00 04 00 00 00 2e 65 6e 76 4d 8e 4d 6f 82 40 18 84 ef fc 0c ef da 6a ad 35 ... > },
  Handler: 'index.handler',
  Role: 'arn:aws:iam::123456789012:role/<lambda_role>',
  Runtime: 'nodejs6.10',
  Description: 'api',
  MemorySize: '128',
  Timeout: '3',
  Publish: false,
  VpcConfig: { SubnetIds: [], SecurityGroupIds: [] },
  Environment: { Variables: null },
  DeadLetterConfig: { TargetArn: null },
  TracingConfig: { Mode: null } }
Key must be a buffer
=> Retrying
{ TypeError: Key must be a buffer
    at TypeError (native)
    at new Hmac (crypto.js:91:16)
    at Object.Hmac (crypto.js:89:12)
    at Object.hmac (/usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/util.js:401:30)
    at Object.getSigningKey (/usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/signers/v4_credentials.js:59:8)
    at V4.signature (/usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/signers/v4.js:97:36)
    at V4.authorization (/usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/signers/v4.js:92:36)
    at V4.addAuthorization (/usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/signers/v4.js:34:12)
    at /usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/event_listeners.js:215:18
    at finish (/usr/lib/node_modules/node-lambda/node_modules/aws-sdk/lib/config.js:315:7) retryDelay: 91.55329953571814 }

I suspect that this is because I am not giving it an IAM account credentials, instead opting to use EC2 roles...

"If your application has AWS credentials baked into it, you're "doing it wrong""