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common.go
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common.go
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package common
import (
"fmt"
"strings"
slsa1 "github.com/in-toto/in-toto-golang/in_toto/slsa_provenance/v1"
serrors "github.com/slsa-framework/slsa-verifier/v2/errors"
)
const (
// ProvenanceV02Type is the SLSA v0.2 predicate type.
ProvenanceV02Type = "https://slsa.dev/provenance/v0.2"
// ProvenanceV1Type is the SLSA v1.0 predicate type.
ProvenanceV1Type = slsa1.PredicateSLSAProvenance
)
// GetWorkflowInputs gets the workflow inputs from the GitHub environment map
// and converts the keys to the necessary casing depending on predicate type.
func GetWorkflowInputs(environment map[string]any, upperEnv bool) (map[string]any, error) {
// Verify it's a workflow_dispatch trigger.
eventKey, err := convertKey("github_event_name", upperEnv)
if err != nil {
return nil, fmt.Errorf("%w: %s",
serrors.ErrorMismatchWorkflowInputs, err)
}
triggerName, err := GetAsString(environment, eventKey)
if err != nil {
return nil, err
}
if triggerName != "workflow_dispatch" {
return nil, fmt.Errorf("%w: expected 'workflow_dispatch' trigger, got %s",
serrors.ErrorMismatchWorkflowInputs, triggerName)
}
payload, err := GetEventPayload(environment, upperEnv)
if err != nil {
return nil, err
}
payloadInputs, err := getAsAny(payload, "inputs")
if err != nil {
return nil, fmt.Errorf("%w: error retrieving 'inputs': %v", serrors.ErrorInvalidDssePayload, err)
}
pyldInputs, ok := payloadInputs.(map[string]interface{})
if !ok {
return nil, fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, "parameters type inputs")
}
return pyldInputs, nil
}
// GetEventPayload retrieves the GitHub event payload from the environment map
// that contains the GitHub context payload.
func GetEventPayload(environment map[string]any, upperEnv bool) (map[string]any, error) {
eventPayloadKey, err := convertKey("github_event_payload", upperEnv)
if err != nil {
return nil, fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
eventPayload, ok := environment[eventPayloadKey]
if !ok {
return nil, fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, "parameters type event payload")
}
payload, ok := eventPayload.(map[string]any)
if !ok {
return nil, fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, "parameters type payload")
}
return payload, nil
}
func convertKey(key string, upperEnv bool) (string, error) {
if upperEnv {
return strings.ToUpper(key), nil
}
return key, nil
}
func getAsAny(environment map[string]any, field string) (any, error) {
value, ok := environment[field]
if !ok {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload,
fmt.Sprintf("environment type for %s", field))
}
return value, nil
}
func getBranchForTag(environment map[string]any, upperEnv bool) (string, error) {
baseRefKey, err := convertKey("github_base_ref", upperEnv)
if err != nil {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
baseRef, err := GetAsString(environment, baseRefKey)
if err != nil {
return "", err
}
// This `base_ref` seems to always be "".
if baseRef != "" {
return baseRef, nil
}
// Look at the event payload instead.
environmentKey, err := convertKey("github_event_name", upperEnv)
if err != nil {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
eventName, err := GetAsString(environment, environmentKey)
if err != nil {
return "", err
}
payload, err := GetEventPayload(environment, upperEnv)
if err != nil {
return "", err
}
// We don't do that for all triggers because the payload
// is event-specific. Only `push` events seem to have a `base_ref`, and
// `release` events specify a branch in `target_commitish`.
switch eventName {
case "push":
value, err := getAsAny(payload, "base_ref")
if err != nil {
return "", err
}
// The `base_ref` field may be nil if the build was from
// a specific commit rather than a branch.
v, ok := value.(string)
if !ok {
return "", nil
}
return v, nil
case "release":
// For a release event, we look for release.target_commitish.
releasePayload, ok := payload["release"]
if !ok {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, "release absent from payload")
}
release, ok := releasePayload.(map[string]interface{})
if !ok {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, "parameters type releasePayload")
}
branch, err := GetAsString(release, "target_commitish")
if err != nil {
return "", fmt.Errorf("%w: %s", err, "target_commitish not present")
}
return "refs/heads/" + branch, nil
default:
return "", nil
}
}
// GetTag returns the triggering event's tag based on the given environment.
func GetTag(environment map[string]any, upperEnv bool) (string, error) {
refTypeKey, err := convertKey("github_ref_type", upperEnv)
if err != nil {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
refType, err := GetAsString(environment, refTypeKey)
if err != nil {
return "", err
}
switch refType {
case "branch":
return "", nil
case "tag":
refKey, err := convertKey("github_ref", upperEnv)
if err != nil {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
return GetAsString(environment, refKey)
default:
return "", fmt.Errorf("%w: %s %q", serrors.ErrorInvalidDssePayload,
"unknown ref type", refType)
}
}
// GetBranch returns the triggering event's branch based on the given environment.
func GetBranch(environment map[string]any, upperEnv bool) (string, error) {
refTypeKey, err := convertKey("github_ref_type", upperEnv)
if err != nil {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
refType, err := GetAsString(environment, refTypeKey)
if err != nil {
return "", err
}
switch refType {
case "branch":
refKey, err := convertKey("github_ref", upperEnv)
if err != nil {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload, err)
}
return GetAsString(environment, refKey)
case "tag":
return getBranchForTag(environment, upperEnv)
default:
return "", fmt.Errorf("%w: %s %q", serrors.ErrorInvalidDssePayload,
"unknown ref type", refType)
}
}
// Exists returns true if the given key exists in the environment.
func Exists(environment map[string]any, field string) bool {
_, ok := environment[field]
return ok
}
// GetAsString returns the value in the given environment as a string.
func GetAsString(environment map[string]any, field string) (string, error) {
value, ok := environment[field]
if !ok {
return "", fmt.Errorf("%w: %s", serrors.ErrorInvalidDssePayload,
fmt.Sprintf("environment type for %s", field))
}
i, ok := value.(string)
if !ok {
return "", fmt.Errorf("%w: %s '%s'", serrors.ErrorInvalidDssePayload, "environment type string", field)
}
return i, nil
}