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Client for the secure login distribution service.

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# shadowc

**shadowc** is a client for [the secure login distribution
service](https://github.com/reconquest/shadowd).

**shadowc** is not a user management tool, shadowc is hash entries manager,
which communicate with **shadowd** server through REST API and request hash
entries for users, afterwards **shadowc** overwrite `/etc/shadow` file with new
hash entries.

## Usage

It's considered that the **shadowd** server is configured earlier and you have
SSL certificate and trusted **shadowd** hosts. If not, [see documentation
here](https://github.com/reconquest/shadowd).

After generating SSL certificate, you should copy `cert.pem` file to client
host into `/etc/shadowc/` directory. But be careful and do not copy private key
`key.pem`, this file should not leave **shadowd** hosts.

**shadowc** can be used either on initial server configuration or for changing
hash entries anytime when you need change passwords.

For running **shadowc** you can specify users which needs update of shadow
entry via `-u <user>` argument, it is possible to specify more than one user.

If you want to request all users from the pool, you can use flag `--all`. Then,
hash entries will be written for each user from the pool which is specified via
`-p`.

Flag `--update` can be used to request new hash entries for users with
non-empty hash in /etc/shadow file. Users without password access or which are
not known to shadowd service will not be updated.

Also you must specify **shadowd** addresses via `-s <addr>` argument. You can
specify more than one server, but all specified addresses should be trusted by
SSL certificate.

If hash tables was generated by tokens with pools you should specify pool name
via `-p <pool>` argument, and **shadowc** will request hashes for users with
this pool.

**shadowc** can create users when needed. Flag `-C` should be added in that
case, which will instruct **shadowc** to create user if it does not exist. By
default, **shadowc** will create user via invocation of `useradd -m
<username>`, but flags for `useradd` can be changed using `-g`. For example,
sudo-user with home dir can be created by passing flag `-g "-m -Gwheel"`.

**shadowc** can also refresh SSH keys, stored in the `authorized_keys` file
per user. Flag `-K` intended to request SSH keys from **shadowd*** server
and add them to the `authorized_keys`. Use `-t` to overwrite file with
new keys, which is more secure way of refreshing keys.

**shadowc** has support of SRV-names, and, by default, if no `-s` specified,
then **shadowc** will try to resolve SRV-record `_shadowd` and try to obtain
info from resulting addresses.

### Additional Options
- `-c <cert>` — set specified certificate file path. (default:
  `/etc/shadowc/cert.pem`)
- `-f <file>` — set specified shadow file path. Can be usable if you use
  `chroot` on your server and shadowc runned outside the `chroot`. (default:
  `/etc/shadow`)

### Examples

Assume that, you have certificate file and two shadowd servers on
`shadowd0.in.example.com:8080` and `shadowd1.in.example.com:8080`, certificate
file has been copied to `/data/shadowc/cert.pem` on target server.

If you want to grant password access for users `john` and `smith` on some
server, you should invoke following command, which will obtain unique hashes
for that server for specified users and place them into `/etc/shadow` file.

After that, `john` and `smith` will be able to connect to the server using
passwords, which were set on **shadowd** server while generating hash tables
for that users.

```
shadowc -s shadowd0.in.example.com:8888 -s shadowd1.in.example.com:8080 \
    -u john -u smith \
    -c /data/shadowc/cert.pem
```

Afterwards shadowc will overwrite the shadow file (`/etc/shadow`) and change
hash entries for John and Smith.

##### Requesting all users from the pool

**shadowc** can request all users from specified pool and it's more convient
way to operate. Flag `--all` should be passed:

```
shadowc -s shadowd.in.example.com:8888 \
    -p production
    --all
```

In that case, if `production` pool contains 10 users, `/etc/passwd` will be
updated for all of them. If there are no such users in `/etc/passwd`, nothing
will be made for them.

##### Creating users automatically

**shadowc** can even create users by running `useradd` for you.
Flag `-C` should be used:

```
shadowc -s shadowd.in.example.com:8888 \
    -p production
    --all
    -C
```

All users from `production` pool will be created (if they are not exists) and
shadow entry will be updated accordingly.

##### Creating privileged users

**shadowc** uses `useradd` for creating users, so it's possible to pass additional
parameters to user creation procedure. Like, if you want to add all your new users
to the `wheel` group, which is most common sudo group, you can use `-g` option:

```
shadowc -s shadowd.in.example.com:8888 \
    -p production
    --all
    -C
    -g "-m -Gwheel"
```

Running in that way **shadowc** will obtain all users from `production` pool,
create them if they are not exists in the system, create home directory for each
user (`-m`) and put each user in the `wheel` group (`-Gwheel`). Then, shadow
entries will be updated.

##### Securely refreshing SSH keys

**shadowc** can manage user's `authorized_keys` file by requesting SSH keys from
**shadowd** server. By default, this behaviour is disabled, by it can be enabled
by specifying option `-K`:

```
shadowc -s shadowd.in.example.com:8888 \
    -p production
    --all
    -C
    -Kt
```

All users from `production` pool will be created (if necessary), shadowd
entries will be updated, SSH keys will be requested and overwritten for that
users.

##### Using default SRV-record

**shadowc** can resolve SRV-records, and, if no `-s` flags are specified, it will
try to resolve `_shadowd` SRV-record and get **shadowd** adresses from resolve
result.

To make use of it, your DNS configuration should have:

* default search domain, e.g. `in.example.com`;
* CNAME `_shadowd.in.example.com` pointing to the shadowd SRV-record;
* SRV-records like:

```
  _shadowd._tcp.in.example.com 60 IN SRV 0 50 443 shadowd-0.in.example.com
  _shadowd._tcp.in.example.com 60 IN SRV 0 50 443 shadowd-1.in.example.com
  ```

If all DNS configured correctly, then, **shadowc** can be invoked without `-s` flag:

```
shadowc -p production -CKt --all
```

This is most consice call that will sync all login info (both password and SSH)
from yours infrastructure **shadowd*** server.

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