5452c32f50
This adds the `agent/connect/ca/plugin` library for consuming/serving Connect CA providers as [go-plugin](https://github.com/hashicorp/go-plugin) plugins. This **does not** wire this up in any way to Consul itself, so this will not enable using these plugins yet. ## Why? We want to enable CA providers to be pluggable without modifying Consul so that any CA or PKI system can potentially back the Connect certificates. This CA system may also be used in the future for easier bootstrapping and internal cluster security. ### go-plugin The benefit of `go-plugin` is that for the plugin consumer, the fact that the interface implementation is communicating over multi-process RPC is invisible. Internals of Consul will continue to just use `ca.Provider` interface implementations as if they're local. For plugin _authors_, they simply have to implement the interface. The network/transport/process management issues are handled by go-plugin itself. The CA provider plugins support both `net/rpc` and gRPC transports. This enables easy authoring in any language. go-plugin handles the actual protocol handshake and connection. This is just a feature of go-plugin. `go-plugin` is already in production use for years by Packer, Terraform, Nomad, Vault, and Sentinel. We've shown stability for both desktop and server-side software. It is very mature. ## Implementation Details ### `map[string]interface{}` The `Configure` method passes a `map[string]interface{}`. This map contains only Go primitives and containers of primitives (no funcs, chans, etc.). For `net/rpc` we encode as-is using Gob. For gRPC we marshal to JSON and transmit as a `bytes` type. This is the same approach we take with Vault and other software. Note that this is just the transport protocol, the end software views it fully decoded. ### `x509.Certificate` and `CertificateRequest` We transmit the raw ASN.1 bytes and decode on the other side. Unit tests are verifying we get the same cert/csrs across the wire. ### Testing `go-plugin` exposes test helpers that enable testing the full plugin RPC over real loopback network connections. We test all endpoints for success and error for both `net/rpc` and gRPC. ### Vendoring This PR doesn't introduce vendoring for two reasons: 1. @banks's `f-envoy` branch introduces a lot of these and I didn't want conflict. 2. The library isn't actually used yet so it doesn't introduce compile-time errors (it does introduce test errors). ## Next Steps With this in place, we need to figure out the proper way to actually hook these up to Consul, load them, etc. This discussion can happen elsewhere, since regardless of approach this plugin library implementation is the exact same.
77 lines
3.6 KiB
Go
77 lines
3.6 KiB
Go
package ca
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import (
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"crypto/x509"
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)
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//go:generate mockery -name Provider -inpkg
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// Provider is the interface for Consul to interact with
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// an external CA that provides leaf certificate signing for
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// given SpiffeIDServices.
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type Provider interface {
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// Configure initializes the provider based on the given cluster ID, root status
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// and configuration values.
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Configure(clusterId string, isRoot bool, rawConfig map[string]interface{}) error
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// GenerateRoot causes the creation of a new root certificate for this provider.
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// This can also be a no-op if a root certificate already exists for the given
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// config. If isRoot is false, calling this method is an error.
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GenerateRoot() error
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// ActiveRoot returns the currently active root CA for this
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// provider. This should be a parent of the certificate returned by
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// ActiveIntermediate()
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ActiveRoot() (string, error)
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// GenerateIntermediateCSR generates a CSR for an intermediate CA
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// certificate, to be signed by the root of another datacenter. If isRoot was
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// set to true with Configure(), calling this is an error.
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GenerateIntermediateCSR() (string, error)
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// SetIntermediate sets the provider to use the given intermediate certificate
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// as well as the root it was signed by. This completes the initialization for
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// a provider where isRoot was set to false in Configure().
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SetIntermediate(intermediatePEM, rootPEM string) error
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// ActiveIntermediate returns the current signing cert used by this provider
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// for generating SPIFFE leaf certs. Note that this must not change except
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// when Consul requests the change via GenerateIntermediate. Changing the
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// signing cert will break Consul's assumptions about which validation paths
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// are active.
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ActiveIntermediate() (string, error)
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// GenerateIntermediate returns a new intermediate signing cert and sets it to
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// the active intermediate. If multiple intermediates are needed to complete
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// the chain from the signing certificate back to the active root, they should
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// all by bundled here.
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GenerateIntermediate() (string, error)
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// Sign signs a leaf certificate used by Connect proxies from a CSR. The PEM
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// returned should include only the leaf certificate as all Intermediates
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// needed to validate it will be added by Consul based on the active
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// intemediate and any cross-signed intermediates managed by Consul.
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Sign(*x509.CertificateRequest) (string, error)
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// SignIntermediate will validate the CSR to ensure the trust domain in the
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// URI SAN matches the local one and that basic constraints for a CA certificate
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// are met. It should return a signed CA certificate with a path length constraint
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// of 0 to ensure that the certificate cannot be used to generate further CA certs.
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SignIntermediate(*x509.CertificateRequest) (string, error)
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// CrossSignCA must accept a CA certificate from another CA provider
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// and cross sign it exactly as it is such that it forms a chain back the the
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// CAProvider's current root. Specifically, the Distinguished Name, Subject
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// Alternative Name, SubjectKeyID and other relevant extensions must be kept.
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// The resulting certificate must have a distinct Serial Number and the
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// AuthorityKeyID set to the CAProvider's current signing key as well as the
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// Issuer related fields changed as necessary. The resulting certificate is
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// returned as a PEM formatted string.
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CrossSignCA(*x509.Certificate) (string, error)
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// Cleanup performs any necessary cleanup that should happen when the provider
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// is shut down permanently, such as removing a temporary PKI backend in Vault
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// created for an intermediate CA.
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Cleanup() error
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}
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