distributed builds: load remote builder host key from the machines file

This is already used by Hydra, and is very useful when materializing
a remote builder list from service discovery. This allows the service
discovery tool to only sync one file instead of two.
This commit is contained in:
Graham Christensen 2021-02-24 20:52:22 -05:00
parent 199081ad00
commit 1130b28824
No known key found for this signature in database
GPG key ID: FE918C3A98C1030F
6 changed files with 33 additions and 6 deletions

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@ -37,7 +37,7 @@ then you need to ensure that the `PATH` of non-interactive login shells
contains Nix.
> **Warning**
>
>
> If you are building via the Nix daemon, it is the Nix daemon user
> account (that is, `root`) that should have SSH access to the remote
> machine. If you cant or dont want to configure `root` to be able to
@ -52,7 +52,7 @@ example, the following command allows you to build a derivation for
```console
$ uname
Linux
$ nix build \
'(with import <nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
--builders 'ssh://mac x86_64-darwin'
@ -103,7 +103,7 @@ default, set it to `-`.
```nix
requiredSystemFeatures = [ "kvm" ];
```
will cause the build to be performed on a machine that has the `kvm`
feature.
@ -112,6 +112,10 @@ default, set it to `-`.
features appear in the derivations `requiredSystemFeatures`
attribute..
8. The (base64-encoded) public host key of the remote machine. If omitted, SSH
will use its regular known-hosts file. Specifically, the field is calculated
via `base64 -w0 /etc/ssh/ssh_host_ed25519_key.pub`.
For example, the machine specification
nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm

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@ -15,6 +15,7 @@ struct LegacySSHStoreConfig : virtual StoreConfig
using StoreConfig::StoreConfig;
const Setting<int> maxConnections{(StoreConfig*) this, 1, "max-connections", "maximum number of concurrent SSH connections"};
const Setting<Path> sshKey{(StoreConfig*) this, "", "ssh-key", "path to an SSH private key"};
const Setting<std::string> sshPublicHostKey{(StoreConfig*) this, "", "base64-ssh-public-host-key", "The public half of the host's SSH key"};
const Setting<bool> compress{(StoreConfig*) this, false, "compress", "whether to compress the connection"};
const Setting<Path> remoteProgram{(StoreConfig*) this, "nix-store", "remote-program", "path to the nix-store executable on the remote system"};
const Setting<std::string> remoteStore{(StoreConfig*) this, "", "remote-store", "URI of the store on the remote system"};
@ -59,6 +60,7 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
, master(
host,
sshKey,
sshPublicHostKey,
// Use SSH master only if using more than 1 connection.
connections->capacity() > 1,
compress,

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@ -54,9 +54,15 @@ ref<Store> Machine::openStore() const {
if (hasPrefix(storeUri, "ssh://")) {
storeParams["max-connections"] = "1";
storeParams["log-fd"] = "4";
}
if (hasPrefix(storeUri, "ssh://") || hasPrefix(storeUri, "ssh-ng://")) {
if (sshKey != "")
storeParams["ssh-key"] = sshKey;
if (sshPublicHostKey != "")
storeParams["base64-ssh-public-host-key"] = sshPublicHostKey;
}
{
auto & fs = storeParams["system-features"];
auto append = [&](auto feats) {

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@ -13,6 +13,7 @@ struct SSHStoreConfig : virtual RemoteStoreConfig
using RemoteStoreConfig::RemoteStoreConfig;
const Setting<Path> sshKey{(StoreConfig*) this, "", "ssh-key", "path to an SSH private key"};
const Setting<std::string> sshPublicHostKey{(StoreConfig*) this, "", "base64-ssh-public-host-key", "The public half of the host's SSH key"};
const Setting<bool> compress{(StoreConfig*) this, false, "compress", "whether to compress the connection"};
const Setting<Path> remoteProgram{(StoreConfig*) this, "nix-daemon", "remote-program", "path to the nix-daemon executable on the remote system"};
const Setting<std::string> remoteStore{(StoreConfig*) this, "", "remote-store", "URI of the store on the remote system"};
@ -34,6 +35,7 @@ public:
, master(
host,
sshKey,
sshPublicHostKey,
// Use SSH master only if using more than 1 connection.
connections->capacity() > 1,
compress)

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@ -2,24 +2,37 @@
namespace nix {
SSHMaster::SSHMaster(const std::string & host, const std::string & keyFile, bool useMaster, bool compress, int logFD)
SSHMaster::SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD)
: host(host)
, fakeSSH(host == "localhost")
, keyFile(keyFile)
, sshPublicHostKey(sshPublicHostKey)
, useMaster(useMaster && !fakeSSH)
, compress(compress)
, logFD(logFD)
{
if (host == "" || hasPrefix(host, "-"))
throw Error("invalid SSH host name '%s'", host);
auto state(state_.lock());
state->tmpDir = std::make_unique<AutoDelete>(createTempDir("", "nix", true, true, 0700));
}
void SSHMaster::addCommonSSHOpts(Strings & args)
{
auto state(state_.lock());
for (auto & i : tokenizeString<Strings>(getEnv("NIX_SSHOPTS").value_or("")))
args.push_back(i);
if (!keyFile.empty())
args.insert(args.end(), {"-i", keyFile});
if (!sshPublicHostKey.empty()) {
Path fileName = (Path) *state->tmpDir + "/host-key";
auto p = host.rfind("@");
string thost = p != string::npos ? string(host, p + 1) : host;
writeFile(fileName, thost + " " + base64Decode(sshPublicHostKey) + "\n");
args.insert(args.end(), {"-oUserKnownHostsFile=" + fileName});
}
if (compress)
args.push_back("-C");
}
@ -87,7 +100,6 @@ Path SSHMaster::startMaster()
if (state->sshMaster != -1) return state->socketPath;
state->tmpDir = std::make_unique<AutoDelete>(createTempDir("", "nix", true, true, 0700));
state->socketPath = (Path) *state->tmpDir + "/ssh.sock";

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@ -12,6 +12,7 @@ private:
const std::string host;
bool fakeSSH;
const std::string keyFile;
const std::string sshPublicHostKey;
const bool useMaster;
const bool compress;
const int logFD;
@ -29,7 +30,7 @@ private:
public:
SSHMaster(const std::string & host, const std::string & keyFile, bool useMaster, bool compress, int logFD = -1);
SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD = -1);
struct Connection
{