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backups: Fix issue with verifying SSH host keys

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Ensure that the fingerprint accepted is the one verified by user. If they
fingerprints and public keys are retrieved separately, there is chance that what
was verified by the user is not what is added to the known hosts file.

- Avoid creating a temporary file when fetching keys

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Joseph Nuthalapati <njoseph@thoughtworks.com>
This commit is contained in:
Sunil Mohan Adapa 2019-06-24 17:25:11 -07:00 committed by Joseph Nuthalapati
parent 463c620c65
commit fa3e2ea86b
No known key found for this signature in database
GPG Key ID: 5398F00A2FA43C35
2 changed files with 13 additions and 22 deletions
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22
plinth/modules/backups/forms.py
View File

@ -199,18 +199,14 @@ class VerifySshHostkeyForm(forms.Form):
def _get_all_public_keys(hostname):
"""Use ssh-keyscan to get all the SSH public keys of a host."""
# Fetch public keys of ssh remote
res1 = subprocess.run(['ssh-keyscan', hostname],
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL, check=True)
with tempfile.NamedTemporaryFile(delete=False) as tmpfil:
tmpfil.write(res1.stdout)
keyscan = subprocess.run(['ssh-keyscan', hostname],
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL)
keys = keyscan.stdout.decode().splitlines()
# Generate user-friendly fingerprints of public keys
res2 = subprocess.run(['ssh-keygen', '-l', '-f', tmpfil.name],
stdout=subprocess.PIPE)
os.remove(tmpfil.name)
keys = res2.stdout.decode().splitlines()
keygen = subprocess.run(['ssh-keygen', '-l', '-f', '-'],
input=keyscan.stdout,
stdout=subprocess.PIPE)
fingerprints = keygen.stdout.decode().splitlines()
# Create a list of tuples of (algorithm, fingerprint)
return [(key.rsplit(' ', 1)[-1].strip('()'), key) for key in keys]
return zip(keys, fingerprints)

13
plinth/modules/backups/views.py
View File

@ -337,19 +337,14 @@ class VerifySshHostkeyView(SuccessMessageMixin, FormView):
return hostname.split('%')[0] # XXX: Likely incorrect to split
@staticmethod
def _add_ssh_hostkey(hostname, key_type):
def _add_ssh_hostkey(ssh_public_key):
"""Add the given SSH key to known_hosts."""
known_hosts_path = get_known_hosts_path()
known_hosts_path.parent.mkdir(parents=True, exist_ok=True)
known_hosts_path.touch()
with known_hosts_path.open('a') as known_hosts_file:
key_line = subprocess.run(
['ssh-keyscan', '-t', key_type, hostname],
stdout=subprocess.PIPE, stderr=subprocess.DEVNULL,
check=True).stdout.decode().strip()
known_hosts_file.write(key_line)
known_hosts_file.write('\n')
known_hosts_file.write(ssh_public_key + '\n')
def get(self, *args, **kwargs):
"""Skip this view if host is already verified."""
@ -361,8 +356,8 @@ class VerifySshHostkeyView(SuccessMessageMixin, FormView):
def form_valid(self, form):
"""Create and store the repository."""
key_type = form.cleaned_data['ssh_public_key']
self._add_ssh_hostkey(self._get_hostname(), key_type)
ssh_public_key = form.cleaned_data['ssh_public_key']
self._add_ssh_hostkey(ssh_public_key)
messages.success(self.request, _('SSH host verified.'))
return self._add_remote_repository()