Support delegations in client #137
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,185 @@ | ||
| package client | ||
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| import ( | ||
| "github.com/theupdateframework/go-tuf/data" | ||
| "github.com/theupdateframework/go-tuf/verify" | ||
| ) | ||
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| // getTargetFileMeta searches for a verified TargetFileMeta matching a file name | ||
| // Requires a local snapshot to be loaded and is locked to the snapshot versions. | ||
| // Searches through delegated targets following TUF spec 1.0.19 section 5.6. | ||
| func (c *Client) getTargetFileMeta(file string) (data.TargetFileMeta, error) { | ||
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| snapshot, err := c.loadLocalSnapshot() | ||
| if err != nil { | ||
| return data.TargetFileMeta{}, err | ||
| } | ||
| verifiers := map[string]verify.DelegationsVerifier{"root": c.db} | ||
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| // delegationsIterator covers 5.6.7 | ||
| // - pre-order depth-first search starting with the top targets | ||
| // - filter delegations with paths or path_hash_prefixes matching searched file | ||
| // - 5.6.7.1 cycles protection | ||
| // - 5.6.7.2 terminations | ||
| delegations := newDelegationsIterator(c.rootTargetDelegation(), "root", file) | ||
| for i := 0; i < c.MaxDelegations; i++ { | ||
| d, ok := delegations.next() | ||
| if !ok { | ||
| return data.TargetFileMeta{}, ErrUnknownTarget{file, snapshot.Version} | ||
| } | ||
| verifier := verifiers[d.parent] | ||
| // covers 5.6.{1,2,3,4,5,6} | ||
| target, err := c.loadDelegatedTargets(snapshot, d.child.Name, verifier) | ||
| if err != nil { | ||
| return data.TargetFileMeta{}, err | ||
| } | ||
| // stop when the searched TargetFileMeta is found | ||
| if m, ok := target.Targets[file]; ok { | ||
| return m, nil | ||
| } | ||
| if target.Delegations != nil { | ||
| delegations.add(target.Delegations.Roles, d.child.Name) | ||
| targetVerifier, err := verify.NewDelegationsVerifier(target.Delegations) | ||
| if err != nil { | ||
| return data.TargetFileMeta{}, err | ||
| } | ||
| verifiers[d.child.Name] = targetVerifier | ||
| } | ||
| } | ||
| return data.TargetFileMeta{}, ErrMaxDelegations{ | ||
| File: file, | ||
| MaxDelegations: c.MaxDelegations, | ||
| SnapshotVersion: snapshot.Version, | ||
| } | ||
| } | ||
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| func (c *Client) loadLocalSnapshot() (*data.Snapshot, error) { | ||
| if err := c.getLocalMeta(); err != nil { | ||
| return nil, err | ||
| } | ||
| rawS, ok := c.localMeta["snapshot.json"] | ||
| if !ok { | ||
| return nil, ErrNoLocalSnapshot | ||
| } | ||
| snapshot := &data.Snapshot{} | ||
| if err := c.db.Unmarshal(rawS, snapshot, "snapshot", c.snapshotVer); err != nil { | ||
| return nil, ErrDecodeFailed{"snapshot.json", err} | ||
| } | ||
| return snapshot, nil | ||
| } | ||
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| // loadDelegatedTargets downloads, decodes, verifies and stores delegated targets | ||
| func (c *Client) loadDelegatedTargets(snapshot *data.Snapshot, role string, verifier verify.DelegationsVerifier) (*data.Targets, error) { | ||
| var err error | ||
| fileName := role + ".json" | ||
| fileMeta, ok := snapshot.Meta[fileName] | ||
| if !ok { | ||
| return nil, ErrRoleNotInSnapshot{role, snapshot.Version} | ||
| } | ||
| // 5.6.1 download target if not in the local store | ||
| // 5.6.2 check against snapshot hash | ||
| raw, alreadyStored := c.localMetaFromSnapshot(fileName, fileMeta) | ||
| if !alreadyStored { | ||
| raw, err = c.downloadMetaFromSnapshot(fileName, fileMeta) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| } | ||
| target := &data.Targets{} | ||
| // 5.6.3 verify signature with parent public keys | ||
| // 5.6.5 verify that the targets is not expired | ||
| if err := verifier.Unmarshal(raw, target, role, fileMeta.Version); err != nil { | ||
| return nil, ErrDecodeFailed{fileName, err} | ||
| } | ||
| // 5.6.4 check against snapshot version | ||
| if target.Version != fileMeta.Version { | ||
| return nil, ErrTargetsSnapshotVersionMismatch{ | ||
| Role: fileName, | ||
| DownloadedTargetsVersion: fileMeta.Version, | ||
| TargetsSnapshotVersion: target.Version, | ||
| SnapshotVersion: snapshot.Version, | ||
| } | ||
| } | ||
| // 5.6.6 persist | ||
| if !alreadyStored { | ||
| if err := c.local.SetMeta(fileName, raw); err != nil { | ||
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| return nil, err | ||
| } | ||
| } | ||
| return target, nil | ||
| } | ||
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| func (c *Client) rootTargetDelegation() data.DelegatedRole { | ||
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| role := "targets" | ||
| r := c.db.GetRole(role) | ||
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| if r == nil { | ||
| return data.DelegatedRole{} | ||
| } | ||
| keyIDs := make([]string, 0, len(r.KeyIDs)) | ||
| for id, _ := range r.KeyIDs { | ||
| keyIDs = append(keyIDs, id) | ||
| } | ||
| return data.DelegatedRole{ | ||
| Name: role, | ||
| KeyIDs: keyIDs, | ||
| Threshold: r.Threshold, | ||
| Paths: []string{"*"}, | ||
| } | ||
| } | ||
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| type delegation struct { | ||
| parent string | ||
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| child data.DelegatedRole | ||
| } | ||
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| type delegationID struct { | ||
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| parent string | ||
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| child string | ||
| } | ||
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| type delegationsIterator struct { | ||
| stack []delegation | ||
| file string | ||
| visited map[delegationID]struct{} | ||
| } | ||
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| func newDelegationsIterator(role data.DelegatedRole, parent string, file string) *delegationsIterator { | ||
| i := &delegationsIterator{ | ||
| file: file, | ||
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| stack: make([]delegation, 0, 1), | ||
| visited: make(map[delegationID]struct{}), | ||
| } | ||
| i.add([]data.DelegatedRole{role}, parent) | ||
| return i | ||
| } | ||
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| func (d *delegationsIterator) next() (delegation, bool) { | ||
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| if len(d.stack) == 0 { | ||
| return delegation{}, false | ||
| } | ||
| delegation := d.stack[len(d.stack)-1] | ||
| d.stack = d.stack[:len(d.stack)-1] | ||
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| // 5.6.7.1 cycles protection | ||
| id := delegationID{delegation.parent, delegation.child.Name} | ||
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| if _, ok := d.visited[id]; ok { | ||
| return d.next() | ||
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| } | ||
| d.visited[id] = struct{}{} | ||
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| // 5.6.7.2 trim delegations to visit, only the current role and its delegations | ||
| // will be considered | ||
| // https://github.com/theupdateframework/specification/issues/168 | ||
| if delegation.child.Terminating { | ||
| d.stack = d.stack[0:0] | ||
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| } | ||
| return delegation, true | ||
| } | ||
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| func (d *delegationsIterator) add(roles []data.DelegatedRole, parent string) { | ||
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| for i := len(roles) - 1; i >= 0; i-- { | ||
| r := roles[i] | ||
| if r.MatchesPath(d.file) { | ||
| d.stack = append(d.stack, delegation{parent, r}) | ||
| } | ||
| } | ||
| } | ||
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