At the bare minimum we should at least improve the documentation in the Cargo book about how the token is used and that the user might need to add the format like Basic or Bearer to the token field.

What I would want to be cautious about is confusing people who don't need this, particularly but the fact that the most common registry people will use does not do this.

An alternative would be to retry the request to the registry prefixing the token with Bearer if there is a 401 response.

I don't know enough about authentication conventions and best practices to weigh on this.

Alternatively, should it be the responsibility of the registry that needs it to advertise the token with the Bearer prefix?

Alternatively, should it be the responsibility of the registry that needs it to advertise the token with the Bearer prefix?

Well I do not disagree with this, but even if the registry does document that the token needs to be sent in Bearer scheme its difficult to know a user to know what authentication scheme Cargo will send it as. I think its not unreasonable to assume Cargo will send a token as Bearer (which it does not) as that is generally the most common scheme for sending tokens in requests.

Perhaps just adding something like this to the Cargo book would be enough to avoid confusion.

NOTE: Cargo will use the token as is in the `Authorization` header without modification. 
For registries that require an authentication scheme like (like Bearer) the `registry.<name>.token` should be prefixed with the scheme name (ie. `Bearer `) by the user.

NOTE: Cargo will use the token as is in the Authorization header without modification.
For registries that require an authentication scheme like (like Bearer) the registry.<name>.token should be prefixed with the scheme name (ie. Bearer ) by the user.

This looks fine, though I would generally recommend private registries moving away from plain token, and use credential provider instead.

Looking at the suggestion, I can see crates.io users being easily confused. imo this is still best documented on the registry.

I can see crates.io users being easily confused.

Hmm yeah that is fair.

imo this is still best documented on the registry.

I have mixed emotions about this. I don't disagree, but at the same time the way Cargo sends token's to the registry is an implementation detail of Cargo so I feel it should at least be documented in Cargo (even if very briefly)

The reason I think this is a problem worth addressing is because its fairly difficult to diagnosis this issue when it happens.
Generally, the registry will respond with a 401 which makes it seem like the token is bad and Cargo (and most registries) do not give any indication that you need to add an authentication scheme.

Hmmm well looking at the docs for JFrog Artifactory (which is what I was using), it does have a code snippet documenting that you do need the Bearer prefix.

Perhaps this was just user error on my part 😓

What about mentioning how Cargo pass the token without talking about auth scheme? We already have it in registry doc:

Perhaps we can expand reference/registry-authentication.md and talk about Cargo setting the "Authorization" header value with the token without modification. And on the doc section of credential file, link to that page with somthing like

 Tokens are used by some Cargo commands such as [`cargo publish`] for
 authenticating with remote registries. Care should be taken to protect the
-tokens and to keep them secret.
+tokens and to keep them secret. See the "Registry Authentication" chapter for
+how the plain text token is used, and other safer authentication alternatives.

That seems reasonable.

I think the reference/registry-authentication.md you linked has the necessary information so having a link to that should make finding that easier for users with authentication issues. 👍

Overall, my expectation is we'd work to deprecate cargo:token in favor of the platform-specific ways of storing credentials which would have both the config and registry authentication documentation updated. This is part of #13343.

However, what authentication methods a registry supports is a choice made by the registry and I don't see getting into the details of the protocol to be helpful to the users but more confusing. It invites questions from the user about how it is relevant. This is why any details beyond "if your registry gives you a token, paste it here" seems like it should belong on the registry side as that narrows the scope to those it affects so it is relevant to them.

I agree we should update the documentation to make it clear that Cargo will send the token as the Authorization header value without an additional scheme.

I'd rather avoid automatically adding the Bearer scheme, as it's not the only scheme (Basic is also common) and it will cause additional unnecessary HTTP requests.