Troubleshoot mTLS certificates

[SVelizMquest]

Question

I'm trying to run a Vegeta attack using certificates for mTLS with the following structure:

echo "POST https://127.0.0.1:8443/eir" | vegeta attack \
  -body=[PATHTOFILE]/testVegeta \
  -cert=[PATHTOFILE]/http_client.crt \
  -duration=30s \
  -http2=true \
  -key=[PATHTOFILE]/http_client.key \
  -max-workers=1 \
  -rate=50/1s \
  -root-certs=[PATHTOFILE]/api_ca.crt | vegeta report

Which is (i think) the equivalent to the following CURL command that does work:

curl -X POST "https://127.0.0.1:8443/eir" \
  -H "Content-type:application/json" \
  -d '{[REQUEST BODY IN testVegeta]}' \
  --cacert [PATHTOFILE]/api/api_ca.crt \
  --cert [PATHTOFILE]/http_client.crt \
  --key [PATHTOFILE]/http_client.key

I'm facing weird problems with Vegeta:

1. The testVegeta file throws "permission denied" when trying to open it unless I leave a space between the "=" and the route. example: '-body= [PATHTOFILE]/testVegeta `. When there isn't a space, it also throws another error that it can't detect the encoding for stdin.
2. Even though they are the exact same certificates, the vegeta requests (when working with the space mentioned in the previous point) throws a http: TLS handshake error from 127.0.0.1:36861: remote error: tls: bad certificate from the server.

I'm using Ubuntu 23.10.
Is this a bug, or is there a mistake in my configurations?
Is there a way to see if Vegeta is opening the files correctly, or a "verbose" option?
Any insight is appreciated.