Tls: failed to verify certificate: x509: certificate signed by unknown authority

terraform plan fails
terraform runs on rhel7 vm which behinds proxy.
the proxy has been set (HTTP_PROXY and HTTPS_PROXY) but still failing. Please assist

│ Error: building account: could not acquire access token to parse claims: clientCredentialsToken: cannot request token: Post https://login.microsoftonline.com/2d95207a-e26f-4141-9832-399482a764a1/oauth2/v2.0/token: POST https://login.microsoftonline.com/2d95207a-e26f-4141-9832-399482a764a1/oauth2/v2.0/token giving up after 5 attempt(s): Post https://login.microsoftonline.com/2d95207a-e26f-4141-9832-399482a764a1/oauth2/v2.0/token: tls: failed to verify certificate: x509: certificate signed by unknown authority

│

│   with provider["registry.terraform.io/hashicorp/azurerm"],

│   on providers.tf line 4, in provider "azurerm":

│    4: provider "azurerm" {

│

╵

ERRO[0017] 1 error occurred:

        * exit status 1