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Documentation/op-guide: clarify security.md on TLS auth 

Make it more accurate (just as pkg/transport/listener_tls.go does).

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>
release-3.4
Gyuho Lee 2018-01-12 14:54:39 -08:00
parent 60e8432807
commit eeb4d35b3f
1 changed files with 5 additions and 11 deletions
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16
Documentation/op-guide/security.md
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@ -197,7 +197,7 @@ When client authentication is enabled for an etcd member, the administrator must
Since [v3.2.0](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v320-2017-06-09), [TLS certificates get reloaded on every client connection](https://github.com/coreos/etcd/pull/7829). This is useful when replacing expiry certs without stopping etcd servers; it can be done by overwriting old certs with new ones. Refreshing certs for every connection should not have too much overhead, but can be improved in the future, with caching layer. Example tests can be found [here](https://github.com/coreos/etcd/blob/b041ce5d514a4b4aaeefbffb008f0c7570a18986/integration/v3_grpc_test.go#L1601-L1757).
Since [v3.2.0](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v320-2017-06-09), [server denies incoming peer certs with wrong IP `SAN`](https://github.com/coreos/etcd/pull/7687). For instance, if peer cert contains IP addresses in Subject Alternative Name (SAN) field, server authenticates a peer only when the remote IP address matches one of those IP addresses. This is to prevent unauthorized endpoints from joining the cluster. For example, peer B's CSR (with `cfssl`) is:
Since [v3.2.0](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v320-2017-06-09), [server denies incoming peer certs with wrong IP `SAN`](https://github.com/coreos/etcd/pull/7687). For instance, if peer cert contains any IP addresses in Subject Alternative Name (SAN) field, server authenticates a peer only when the remote IP address matches one of those IP addresses. This is to prevent unauthorized endpoints from joining the cluster. For example, peer B's CSR (with `cfssl`) is:
```json
{
@ -223,16 +223,14 @@ Since [v3.2.0](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v320-2017
when peer B's actual IP address is `10.138.0.2`, not `10.138.0.27`. When peer B tries to join the cluster, peer A will reject B with the error `x509: certificate is valid for 10.138.0.27, not 10.138.0.2`, because B's remote IP address does not match the one in Subject Alternative Name (SAN) field.
Since [v3.2.0](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v320-2017-06-09), [server resolves TLS `DNSNames` when checking `SAN`](https://github.com/coreos/etcd/pull/7767). For instance, if peer cert contains any DNS names in Subject Alternative Name (SAN) field, server authenticates a peer only when forward-lookups on those DNS names have matching IP with the remote IP address. For example, peer B's CSR (with `cfssl`) is:
Since [v3.2.0](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v320-2017-06-09), [server resolves TLS `DNSNames` when checking `SAN`](https://github.com/coreos/etcd/pull/7767). For instance, if peer cert contains only DNS names (no IP addresses) in Subject Alternative Name (SAN) field, server authenticates a peer only when forward-lookups (`dig b.com`) on those DNS names have matching IP with the remote IP address. For example, peer B's CSR (with `cfssl`) is:
```json
{
...
"CN": "etcd peer",
"hosts": [
"b.com"
],
...
}
```
when peer B's remote IP address is `10.138.0.2`. When peer B tries to join the cluster, peer A looks up the incoming host `b.com` to get the list of IP addresses (e.g. `dig b.com`). And rejects B if the list does not contain the IP `10.138.0.2`, with the error `tls: 10.138.0.2 does not match any of DNSNames ["b.com"]`.
@ -241,13 +239,11 @@ Since [v3.2.2](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v322-2017
```json
{
...
"CN": "etcd peer",
"hosts": [
"invalid.domain",
"10.138.0.2"
],
...
}
```
when peer B's remote IP address is `10.138.0.2` and `invalid.domain` is a invalid host. When peer B tries to join the cluster, peer A successfully authenticates B, since Subject Alternative Name (SAN) field has a valid matching IP address. See [issue#8206](https://github.com/coreos/etcd/issues/8206) for more detail.
@ -256,13 +252,11 @@ Since [v3.2.5](https://github.com/coreos/etcd/blob/master/CHANGELOG.md#v325-2017
```json
{
...
"CN": "etcd peer",
"hosts": [
"*.example.default.svc",
"*.example.default.svc.cluster.local"
],
...
}
```
when peer B's remote IP address is `10.138.0.2`. When peer B tries to join the cluster, peer A reverse-lookup the IP `10.138.0.2` to get the list of host names. And either exact or wildcard match the host names with peer B's cert DNS names in Subject Alternative Name (SAN) field. If none of reverse/forward lookups worked, it returns an error `"tls: "10.138.0.2" does not match any of DNSNames ["*.example.default.svc","*.example.default.svc.cluster.local"]`. See [issue#8268](https://github.com/coreos/etcd/issues/8268) for more detail.