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| 1 | package ssh |
| 2 | |
| 3 | // The key a job acts with. |
| 4 | // |
| 5 | // A workflow that names `acts-as: <account>` gets a credential for that account |
| 6 | // when the job is leased: an ed25519 pair generated here, the public half stored in |
| 7 | // the queue with the run, repository and expiry, and the private half sent on the |
| 8 | // lease channel. The runner writes it into the job's run directory, so a step's |
| 9 | // `git push` or `vole issue comment` authenticates as the account without the |
| 10 | // repository holding a long-lived key. |
| 11 | // |
| 12 | // Two checks decide whether the job can have it: the account must exist, be active, |
| 13 | // and be a bot account. The role it may act with is not decided here — the hook |
| 14 | // applies the same role rules to a credential session that it applies to the |
| 15 | // account's own key, so a job cannot act as more than its account may. |
| 16 | |
| 17 | import ( |
| 18 | "crypto/ed25519" |
| 19 | "crypto/rand" |
| 20 | "encoding/pem" |
| 21 | "fmt" |
| 22 | "time" |
| 23 | |
| 24 | xssh "golang.org/x/crypto/ssh" |
| 25 | "rodent.software/vole/ci/runs" |
| 26 | ) |
| 27 | |
| 28 | const ( |
| 29 | // credentialGrace is how long a run's key remains valid after the job's own |
| 30 | // budget ends. A step may need to push its last commit after the last step, and |
| 31 | // the runner's finish is what normally ends the key; this is the backstop for a |
| 32 | // runner that dies without one. |
| 33 | credentialGrace = 30 * time.Minute |
| 34 | // credentialMin and credentialMax bound the backstop. A run with no budget gets |
| 35 | // the minimum; a long one is still capped, so a key cannot outlive its job by a |
| 36 | // working day. |
| 37 | credentialMin = time.Hour |
| 38 | credentialMax = 6 * time.Hour |
| 39 | ) |
| 40 | |
| 41 | // mintCredential issues a key for one run and returns the private half and the |
| 42 | // instance's host key line. A non-empty reason means the run asked for an account it |
| 43 | // cannot have, and the job fails with that line instead of running without a key. |
| 44 | func (s *Server) mintCredential(run *runs.Run, now time.Time) (*runnerCredential, string, string) { |
| 45 | acct, err := s.cfg.Identity.Find(run.Bot) |
| 46 | if err != nil || acct == nil { |
| 47 | return nil, "", fmt.Sprintf("this job acts as %s, which is not an account on this instance", run.Bot) |
| 48 | } |
| 49 | if !acct.Active() { |
| 50 | return nil, "", fmt.Sprintf("this job acts as %s, which is retired", run.Bot) |
| 51 | } |
| 52 | if !acct.Bot() { |
| 53 | return nil, "", fmt.Sprintf("this job acts as %s, which is not a bot account", run.Bot) |
| 54 | } |
| 55 | pub, priv, err := ed25519.GenerateKey(rand.Reader) |
| 56 | if err != nil { |
| 57 | return nil, "", "cannot generate a credential: " + err.Error() |
| 58 | } |
| 59 | publicKey, err := xssh.NewPublicKey(pub) |
| 60 | if err != nil { |
| 61 | return nil, "", "cannot prepare a credential: " + err.Error() |
| 62 | } |
| 63 | block, err := xssh.MarshalPrivateKey(priv, "vole run "+run.ID) |
| 64 | if err != nil { |
| 65 | return nil, "", "cannot encode a credential: " + err.Error() |
| 66 | } |
| 67 | fingerprint := xssh.FingerprintSHA256(publicKey) |
| 68 | if err := s.cfg.Runs.SetRunCredential(runs.RunCredential{ |
| 69 | Fingerprint: fingerprint, |
| 70 | Account: run.Bot, |
| 71 | Repo: run.Repo, |
| 72 | RunID: run.ID, |
| 73 | Expires: now.Add(credentialTTL(run.Timeout)), |
| 74 | }, now); err != nil { |
| 75 | return nil, "", "cannot record a credential: " + err.Error() |
| 76 | } |
| 77 | return &runnerCredential{ |
| 78 | PrivateKey: string(pem.EncodeToMemory(block)), |
| 79 | Fingerprint: fingerprint, |
| 80 | }, s.hostKey, "" |
| 81 | } |
| 82 | |
| 83 | // credentialTTL is how long a run's key may live: its own budget plus a grace, so a |
| 84 | // step that pushes at the end of the budget is not cut off, bounded at both ends. |
| 85 | func credentialTTL(budget string) time.Duration { |
| 86 | ttl := credentialMin |
| 87 | if d, err := time.ParseDuration(budget); err == nil && d > 0 { |
| 88 | ttl = d |
| 89 | } |
| 90 | return min(ttl+credentialGrace, credentialMax) |
| 91 | } |
| 92 |