docker - 如何在 Alpine 上的 OpenSSH 中调试无效的无密码 RSA 证书？

Question

我计划使用真正的 SSH 客户端和 SSH 服务器编写和运行一些集成测试。由于这需要服务器级别的配置，我在 Docker 中设置测试，因此可以按照正确的规范构建服务器，启动 OpenSSH 服务器，然后运行测试。

我系统的一部分需要非 root 用户(称为 nonpriv )才能使用 ssh在无密码的基础上进入服务器。我已经生成了服务器证书和非 root 用户证书。我设置了localhost作为已知主机(因此服务器真实性已得到确认)，但我正在努力将证书设置为授权 key 。我希望能够做到ssh localhost作为 nonpriv用户并自动获取外壳。但是它正在跳过 key 并进入密码验证，这不是我想要的。

docker ENTRYPOINT是这样的，因此每次运行的服务器 key 都不同:

#!/bin/sh
#
# With thanks to https://github.com/danielguerra69/alpine-sshd

if [ ! -f "/etc/ssh/ssh_host_rsa_key" ]; then
    # generate fresh rsa key
    ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -t rsa
fi

if [ ! -f "/etc/ssh/ssh_host_dsa_key" ]; then
    # generate fresh dsa key
    ssh-keygen -f /etc/ssh/ssh_host_dsa_key -N '' -t dsa
fi

# Prepare run dir
if [ ! -d "/var/run/sshd" ]; then
  mkdir -p /var/run/sshd
fi

# Start the SSH daemon
/usr/sbin/sshd

# Generate an SSH key for the nonpriv user
su -c /tmp/install/generate-keys.sh nonpriv

# Sleep so we can debug the server while it is running
# Will be replaced by test runner when SSH client works!
sleep 10000

与 Docker 一样，这一切都以 root 运行。 ，所以我使用 su -c最后生成用户 key :

#!/bin/sh

mkdir -p /home/nonpriv/.ssh

# Add the server to recognised hosts
ssh-keyscan localhost >> /home/nonpriv/.ssh/known_hosts

# Generate an SSH key with an empty passphrase
ssh-keygen \
    -t rsa \
    -b 4096 \
    -f /home/nonpriv/.ssh/id_rsa \
    -N ''

# Add it to the list of authorised keys for self
ln -s /home/nonpriv/.ssh/id_rsa.pub /home/nonpriv/.ssh/authorized_keys

如您所见，我使用符号链接(symbolic link)将公钥添加到授权 key 列表中。然后我运行 Docker 容器和 shell(其中“silly_name”是自动生成的容器名称):

docker exec -it silly_name sh

从外壳我这样做:

/ # whoami
root
/ # su nonpriv
/ $ whoami
nonpriv
/ $ ssh -vvv localhost
OpenSSH_7.4p1, LibreSSL 2.4.4
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "localhost" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to localhost [::1] port 22.
debug1: Connection established.
debug1: identity file /home/nonpriv/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/nonpriv/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to localhost:22 as 'nonpriv'
debug3: hostkeys_foreach: reading file "/home/nonpriv/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/nonpriv/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from localhost
debug3: order_hostkeyalgs: prefer hostkeyalgs: ssh-rsa-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ssh-rsa-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: rsa-sha2-512
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ssh-rsa SHA256:ierfDQtTWiobxAGsyEf1PrjRcmsr5jQbZVOzcNCnBo4
debug3: hostkeys_foreach: reading file "/home/nonpriv/.ssh/known_hosts"
debug3: record_hostkey: found key type RSA in file /home/nonpriv/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from localhost
debug1: Host 'localhost' is known and matches the RSA host key.
debug1: Found key in /home/nonpriv/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /home/nonpriv/.ssh/id_rsa (0x5645c099ae80)
debug2: key: /home/nonpriv/.ssh/id_dsa (0)
debug2: key: /home/nonpriv/.ssh/id_ecdsa (0)
debug2: key: /home/nonpriv/.ssh/id_ed25519 (0)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug3: start over, passed a different list publickey,password,keyboard-interactive
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/nonpriv/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Trying private key: /home/nonpriv/.ssh/id_dsa
debug3: no such identity: /home/nonpriv/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/nonpriv/.ssh/id_ecdsa
debug3: no such identity: /home/nonpriv/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/nonpriv/.ssh/id_ed25519
debug3: no such identity: /home/nonpriv/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: 
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
nonpriv@localhost's password: 

由此可见 /home/nonpriv/.ssh/id_rsa可用，但不成功。我在 Internet 上尝试了许多资源，通常与主目录或 ~/.ssh 的权限有关。文件夹，或 authorized_keys文件，但无济于事。我会继续尝试，但从系统中获取一些关于问题可能是什么的信息会很有用。

我认为可以设置 key 以使 ssh-ing 进入 localhost，因为我已经在我的开发笔记本电脑中完成了此操作(诚然，使用 Mint 18 作为操作系统而不是 Alpine/BusyBox)。

不幸的是， /var/log/ 中根本没有日志。 ，所以这里没有太多信息可以继续。我接下来可以看哪里？

更新

如果 sshd 配置可能很重要，我有来自 Alpine 的默认配置:

$ less /etc/ssh/sshd_config

#   $OpenBSD: sshd_config,v 1.100 2016/08/15 12:32:04 naddy Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/bin:/usr/bin:/sbin:/usr/sbin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key

# Ciphers and keying
#RekeyLimit default none

# Logging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#PubkeyAuthentication yes

# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
# but this is overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile  .ssh/authorized_keys

#AuthorizedPrincipalsFile none

#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
#UsePAM no

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
#X11Forwarding no
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation sandbox
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS no
#PidFile /run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none

# override default of no subsystems
Subsystem   sftp    /usr/lib/ssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#   X11Forwarding no
#   AllowTcpForwarding no
#   PermitTTY no
#   ForceCommand cvs server

Answer 1

我已经解决了这个问题，尽管我不完全理解为什么会解决它。 (如果有人有解释，我会优先接受任何答案，而不是我自己的答案)。

在我的 Dockerfile我正在设置一个用户:

# -s specify a shell; -D = don't prompt for a password
RUN adduser -s /bin/sh -D nonpriv

据我所知，这只是一个拥有主目录和空密码的用户。但是，看起来我确实需要指定密码，所以我现在也这样做:

# It looks like passwordless access does not work unless the user
# has a password!
RUN echo 'nonpriv:Password123' | chpasswd

这对我来说似乎很奇怪，因为 PPK 访问系统不应该关心用户的密码是什么，或者它是否有密码。

我现在可以通过 SSH 连接到自己:

/ $ whoami
nonpriv
/ $ ssh localhost
Welcome to Alpine!

The Alpine Wiki contains a large amount of how-to guides and general
information about administrating Alpine systems.
See <http://wiki.alpinelinux.org>.

You can setup the system with the command: setup-alpine

You may change this message by editing /etc/motd.

d4dded05c2d1:~$