terraform/internal/getproviders/hash.go

158 lines
6.5 KiB
Go

package getproviders
import (
"fmt"
"path/filepath"
"strings"
"golang.org/x/mod/sumdb/dirhash"
)
// PackageHash computes a hash of the contents of the package at the given
// location, using whichever hash algorithm is the current default.
//
// Currently, this method returns version 1 hashes as produced by the
// function PackageHashV1, but this function may switch to other versions in
// later releases. Call PackageHashV1 directly if you specifically need a V1
// hash.
//
// PackageHash can be used only with the two local package location types
// PackageLocalDir and PackageLocalArchive, because it needs to access the
// contents of the indicated package in order to compute the hash. If given
// a non-local location this function will always return an error.
func PackageHash(loc PackageLocation) (string, error) {
return PackageHashV1(loc)
}
// PackageMatchesHash returns true if the package at the given location matches
// the given hash, or false otherwise.
//
// If it cannot read from the given location, or if the given hash is in an
// unsupported format, PackageMatchesHash returns an error.
//
// There is currently only one hash format, as implemented by HashV1. However,
// if others are introduced in future PackageMatchesHash may accept multiple
// formats, and may generate errors for any formats that become obsolete.
//
// PackageMatchesHash can be used only with the two local package location types
// PackageLocalDir and PackageLocalArchive, because it needs to access the
// contents of the indicated package in order to compute the hash. If given
// a non-local location this function will always return an error.
func PackageMatchesHash(loc PackageLocation, want string) (bool, error) {
switch {
case strings.HasPrefix(want, "h1"):
got, err := PackageHashV1(loc)
if err != nil {
return false, err
}
return got == want, nil
default:
return false, fmt.Errorf("unsupported hash format (this may require a newer version of Terraform)")
}
}
// PackageHashV1 computes a hash of the contents of the package at the given
// location using hash algorithm 1.
//
// The hash covers the paths to files in the directory and the contents of
// those files. It does not cover other metadata about the files, such as
// permissions.
//
// This function is named "PackageHashV1" in anticipation of other hashing
// algorithms being added in a backward-compatible way in future. The result
// from PackageHashV1 always begins with the prefix "h1:" so that callers can
// distinguish the results of potentially multiple different hash algorithms in
// future.
//
// PackageHashV1 can be used only with the two local package location types
// PackageLocalDir and PackageLocalArchive, because it needs to access the
// contents of the indicated package in order to compute the hash. If given
// a non-local location this function will always return an error.
func PackageHashV1(loc PackageLocation) (string, error) {
// Our HashV1 is really just the Go Modules hash version 1, which is
// sufficient for our needs and already well-used for identity of
// Go Modules distribution packages. It is also blocked from incompatible
// changes by being used in a wide array of go.sum files already.
//
// In particular, it also supports computing an equivalent hash from
// an unpacked zip file, which is not important for Terraform workflow
// today but is likely to become so in future if we adopt a top-level
// lockfile mechanism that is intended to be checked in to version control,
// rather than just a transient lock for a particular local cache directory.
// (In that case we'd need to check hashes of _packed_ packages, too.)
//
// Internally, dirhash.Hash1 produces a string containing a sequence of
// newline-separated path+filehash pairs for all of the files in the
// directory, and then finally produces a hash of that string to return.
// In both cases, the hash algorithm is SHA256.
switch loc := loc.(type) {
case PackageLocalDir:
// We'll first dereference a possible symlink at our PackageDir location,
// as would be created if this package were linked in from another cache.
packageDir, err := filepath.EvalSymlinks(string(loc))
if err != nil {
return "", err
}
return dirhash.HashDir(packageDir, "", dirhash.Hash1)
case PackageLocalArchive:
archivePath, err := filepath.EvalSymlinks(string(loc))
if err != nil {
return "", err
}
return dirhash.HashZip(archivePath, dirhash.Hash1)
default:
return "", fmt.Errorf("cannot hash package at %s", loc.String())
}
}
// Hash computes a hash of the contents of the package at the location
// associated with the reciever, using whichever hash algorithm is the current
// default.
//
// This method will change to use new hash versions as they are introduced
// in future. If you need a specific hash version, call the method for that
// version directly instead, such as HashV1.
//
// Hash can be used only with the two local package location types
// PackageLocalDir and PackageLocalArchive, because it needs to access the
// contents of the indicated package in order to compute the hash. If given
// a non-local location this function will always return an error.
func (m PackageMeta) Hash() (string, error) {
return PackageHash(m.Location)
}
// MatchesHash returns true if the package at the location associated with
// the receiver matches the given hash, or false otherwise.
//
// If it cannot read from the given location, or if the given hash is in an
// unsupported format, MatchesHash returns an error.
//
// MatchesHash can be used only with the two local package location types
// PackageLocalDir and PackageLocalArchive, because it needs to access the
// contents of the indicated package in order to compute the hash. If given
// a non-local location this function will always return an error.
func (m PackageMeta) MatchesHash(want string) (bool, error) {
return PackageMatchesHash(m.Location, want)
}
// HashV1 computes a hash of the contents of the package at the location
// associated with the receiver using hash algorithm 1.
//
// The hash covers the paths to files in the directory and the contents of
// those files. It does not cover other metadata about the files, such as
// permissions.
//
// HashV1 can be used only with the two local package location types
// PackageLocalDir and PackageLocalArchive, because it needs to access the
// contents of the indicated package in order to compute the hash. If given
// a non-local location this function will always return an error.
func (m PackageMeta) HashV1() (string, error) {
return PackageHashV1(m.Location)
}