Improved security

Dockerfile

@@ -1,15 +1,15 @@
 FROM debian:jessie
 MAINTAINER Adrian Dvergsdal [atmoz.net]
 
+# - Install packages
+# - OpenSSH needs /var/run/sshd to run
+# - Remove generic host keys, entrypoint generates unique keys
 RUN apt-get update && \
-    DEBIAN_FRONTEND=noninteractive apt-get -y install openssh-server && \
+    apt-get -y install openssh-server && \
+    mkdir -p /var/run/sshd && \
+    rm -f /etc/ssh/ssh_host_*key* && \
     rm -rf /var/lib/apt/lists/*
 
-# Step 1: sshd needs /var/run/sshd/ to run
-# Step 2: Remove keys, they will be generated later by entrypoint
-#         (unique keys for each container)
-RUN mkdir -p /var/run/sshd && \
-    rm /etc/ssh/ssh_host_*key*
 
 COPY sshd_config /etc/ssh/sshd_config
 COPY entrypoint /

entrypoint

@@ -116,8 +116,13 @@ if [ ! -f "$userConfFinalPath" ]; then
         createUser "$user"
     done < "$userConfFinalPath"
 
-    # Generate unique ssh keys for this container
+    # Generate unique ssh keys for this container, if needed
-    dpkg-reconfigure openssh-server
+    if [ ! -f /etc/ssh/ssh_host_ed25519_key ]; then
+        ssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key < /dev/null
+    fi
+    if [ ! -f /etc/ssh/ssh_host_rsa_key ]; then
+        ssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key < /dev/null
+    fi
 fi
 
 # Source custom scripts, if any

sshd_config

@@ -1,7 +1,22 @@
+# Secure defaults
+# See: https://stribika.github.io/2015/01/04/secure-secure-shell.html
+Protocol 2
+HostKey /etc/ssh/ssh_host_ed25519_key
+HostKey /etc/ssh/ssh_host_rsa_key
+
+# Faster connection
+# See: https://github.com/atmoz/sftp/issues/11
 UseDNS no
+
+# Limited access
 PermitRootLogin no
-Subsystem sftp internal-sftp
-ChrootDirectory %h
 X11Forwarding no
 AllowTcpForwarding no
+
+# Force sftp and chroot jail
+Subsystem sftp internal-sftp
 ForceCommand internal-sftp
+ChrootDirectory %h
+
+# Enable this for more logs
+#LogLevel VERBOSE

tests/run

@@ -24,6 +24,10 @@ fi
 function beforeTest() {
     if [ "$build" == "build" ]; then
         docker build --pull=true --tag "$sftpImageName" "$buildDir"
+        if [ $? -gt 0 ]; then
+            echo "Build failed"
+            exit 1
+        fi
     fi
 
     # Private key can not be read by others
@@ -41,7 +45,7 @@ function beforeTest() {
         --expose 22 \
         -d "$sftpImageName" \
         > "$redirect"
-    sleep 1 # wait for sftp server to get ready
+    sleep 2 # wait for sftp server to get ready
 }
 
 function afterTest() {
@@ -76,6 +80,8 @@ function runSftpCommands() {
         -oUserKnownHostsFile=/dev/null \
         -b - $user@$ip \
         > "$redirect" 2>&1
+
+    sleep 1 # wait for command to finish
 }
 
 ##############################################################################
@@ -90,7 +96,7 @@ function testMinimalContainerStart() {
         -d "$sftpImageName" \
         minimal \
         > "$redirect"
-    sleep 1
+    sleep 2
 
     ps="$(docker ps -q -f name="$tmpContainerName")"
     assertNotEqual "$ps" ""
@@ -157,7 +163,7 @@ function testCustomContainerStart() {
         -d "$sftpImageName" \
         custom:123 \
         > "$redirect"
-    sleep 1
+    sleep 2
 
     ps="$(docker ps -q -f name="$tmpContainerName")"
     assertNotEqual "$ps" ""