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fix!: use names not IDs for agent SSH key seed #17258

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Merged
merged 1 commit into from
Apr 4, 2025
Merged

fix!: use names not IDs for agent SSH key seed #17258

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fix: use names not IDs for agent SSH key seed
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@spikecurtis
spikecurtis committed Apr 4, 2025
commit c97ff5c859c494a91c279863487a775e15ddd377
29 changes: 24 additions & 5 deletions agent/agent.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1186,9 +1186,9 @@ func (a *agent) createOrUpdateNetwork(manifestOK, networkOK *checkpoint) func(co
network := a.network
a.closeMutex.Unlock()
if network == nil {
keySeed, err := WorkspaceKeySeed(manifest.WorkspaceID, manifest.AgentName)
keySeed, err := SSHKeySeed(manifest.OwnerName, manifest.WorkspaceName, manifest.AgentName)
if err != nil {
return xerrors.Errorf("generate seed from workspace id: %w", err)
return xerrors.Errorf("generate SSH key seed: %w", err)
}
// use the graceful context here, because creating the tailnet is not itself tied to the
// agent API.
Expand Down Expand Up @@ -2068,12 +2068,31 @@ func PrometheusMetricsHandler(prometheusRegistry *prometheus.Registry, logger sl
})
}

// WorkspaceKeySeed converts a WorkspaceID UUID and agent name to an int64 hash.
// SSHKeySeed converts an owner userName, workspaceName and agentName to an int64 hash.
// This uses the FNV-1a hash algorithm which provides decent distribution and collision
// resistance for string inputs.
func WorkspaceKeySeed(workspaceID uuid.UUID, agentName string) (int64, error) {
//
// Why owner username, workspace name, and agent name? These are the components that are used in hostnames for the
// workspace over SSH, and so we want the workspace to have a stable key with respect to these. We don't use the
// respective UUIDs. The workspace UUID would be different if you delete and recreate a workspace with the same name.
// The agent UUID is regenerated on each build. Since Coder's Tailnet networking is handling the authentication, we
// should not be showing users warnings about host SSH keys.
func SSHKeySeed(userName, workspaceName, agentName string) (int64, error) {
h := fnv.New64a()
_, err := h.Write(workspaceID[:])
_, err := h.Write([]byte(userName))
if err != nil {
return 42, err
}
// null separators between strings so that (dog, foodstuff) is distinct from (dogfood, stuff)
_, err = h.Write([]byte{0})
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if err != nil {
return 42, err
}
_, err = h.Write([]byte(workspaceName))
if err != nil {
return 42, err
}
_, err = h.Write([]byte{0})
if err != nil {
return 42, err
}
Expand Down
5 changes: 4 additions & 1 deletion cli/ssh_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -479,6 +479,9 @@ func TestSSH(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), testutil.WaitLong)
defer cancel()

user, err := client.User(ctx, codersdk.Me)
require.NoError(t, err)

inv, root := clitest.New(t, "ssh", "--stdio", workspace.Name)
clitest.SetupConfig(t, client, root)
inv.Stdin = clientOutput
Expand All @@ -490,7 +493,7 @@ func TestSSH(t *testing.T) {
assert.NoError(t, err)
})

keySeed, err := agent.WorkspaceKeySeed(workspace.ID, "dev")
keySeed, err := agent.SSHKeySeed(user.Username, workspace.Name, "dev")
assert.NoError(t, err)

signer, err := agentssh.CoderSigner(keySeed)
Expand Down
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