FTP、CentOS 和 SELinux 权限

Question 1

@djangofan 我不知道 SSHD ftp 子系统是否允许将用户 chrooting 到特定目录...但也许...

@Peter - 尝试查看 /var/log/vsftpd.log 并查看当用户尝试在其 chrooted 目录（/var/www/html）内创建目录时会发生什么 - 它应该记录一些内容，权限、无效响应、无法获取目录列表等。此外，尝试将您的 FTP 客户端设置为PASSIVE模式，这似乎可以解决很多与 FTP 相关的问题。

另外，我希望您正在 chroot 用户，而不是授予完整的系统 FTP 访问权限……这非常危险，您可能有一天会后悔（FTP 极其不安全，默认情况下通过纯文本发送凭据 - 如果您启用 SSL 包装器，那么它会更安全，但仍然拥有完整的系统 FTP 访问权限并不好）。如果您确实需要完整的系统访问权限，并且需要本机权限设置和易用性，请签出 SCP 登录，它使用 SSH（安全）登录，并且用户仅限于您在文件系统中设置的任何权限（与 /etc/passwd 中的用户相同）。

我之前在设置 vsftpd 时遇到过问题（这可能很棘手）...

下面是我的工作系统中将用户 chroot 到目录结构的示例配置：

# Example config file /etc/vsftpd/vsftpd.conf
#
# The default compiled in settings are fairly paranoid. This sample file
# loosens things up a bit, to make the ftp daemon more usable.
# Please see vsftpd.conf.5 for all compiled in defaults.
#
# READ THIS: This example file is NOT an exhaustive list of vsftpd options.
# Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's
# capabilities.
#
# Allow anonymous FTP? (Beware - allowed by default if you comment this out).anonymous_enable=NO
#
# Uncomment this to allow local users to log in.
local_enable=YES
local_root=/var/www
#
# Uncomment this to enable any form of FTP write command.
write_enable=YES
#
# Default umask for local users is 077. You may wish to change this to 022,
# if your users expect that (022 is used by most other ftpd's)
local_umask=022
#
# Uncomment this to allow the anonymous FTP user to upload files. This only
# has an effect if the above global write enable is activated. Also, you will
# obviously need to create a directory writable by the FTP user.
#anon_upload_enable=YES
#
# Uncomment this if you want the anonymous FTP user to be able to create
# new directories.
#anon_mkdir_write_enable=YES
#
# Activate directory messages - messages given to remote users when they
# go into a certain directory.
dirmessage_enable=YES
#
# Activate logging of uploads/downloads.
# The target log file can be vsftpd_log_file or xferlog_file.
# This depends on setting xferlog_std_format parameter
xferlog_enable=YES
#
# Make sure PORT transfer connections originate from port 20 (ftp-data).
connect_from_port_20=YES
#
# If you want, you can arrange for uploaded anonymous files to be owned by
# a different user. Note! Using "root" for uploaded files is not
# recommended!
#chown_uploads=YES
#chown_username=whoever
#
# The name of log file when xferlog_enable=YES and xferlog_std_format=YES
# WARNING - changing this filename affects /etc/logrotate.d/vsftpd.log
#xferlog_file=/var/log/xferlog
#
# Switches between logging into vsftpd_log_file and xferlog_file files.
# NO writes to vsftpd_log_file, YES to xferlog_file
xferlog_std_format=NO
#
# You may change the default value for timing out an idle session.
#idle_session_timeout=600
#
# You may change the default value for timing out a data connection.
#data_connection_timeout=120
#
# It is recommended that you define on your system a unique user which the
# ftp server can use as a totally isolated and unprivileged user.
#nopriv_user=ftpsecure
#
# Enable this and the server will recognise asynchronous ABOR requests. Not
# recommended for security (the code is non-trivial). Not enabling it,
# however, may confuse older FTP clients.
#async_abor_enable=YES
#
# By default the server will pretend to allow ASCII mode but in fact ignore
# the request. Turn on the below options to have the server actually do ASCII
# mangling on files when in ASCII mode.
# Beware that turning on ascii_download_enable enables malicious remote parties
# to consume your I/O resources, by issuing the command "SIZE /big/file" in
# ASCII mode.
# These ASCII options are split into upload and download because you may wish
# to enable ASCII uploads (to prevent uploaded scripts etc. from breaking),
# without the DoS risk of SIZE and ASCII downloads. ASCII mangling should be
# on the client anyway..
#ascii_upload_enable=YES
#ascii_download_enable=YES
#
# You may fully customise the login banner string:
#ftpd_banner=Welcome to blah FTP service.
#
# You may specify a file of disallowed anonymous e-mail addresses. Apparently
# useful for combatting certain DoS attacks.
#deny_email_enable=YES
# (default follows)
#banned_email_file=/etc/vsftpd.banned_emails
#
# You may specify an explicit list of local users to chroot() to their home
# directory. If chroot_local_user is YES, then this list becomes a list of
# users to NOT chroot().
chroot_local_user=YES
#chroot_list_enable=YES
# (default follows)
#chroot_list_file=/etc/vsftpd.chroot_list
#
# You may activate the "-R" option to the builtin ls. This is disabled by
# default to avoid remote users being able to cause excessive I/O on large
# sites. However, some broken FTP clients such as "ncftp" and "mirror" assume
# the presence of the "-R" option, so there is a strong case for enabling it.
#ls_recurse_enable=YES

pam_service_name=vsftpd
userlist_enable=YES
#enable for standalone mode
listen=YES
tcp_wrappers=YES
user_config_dir=/var/www/users
log_ftp_protocol=YES
check_shell=NO

下面是 user_config_dir (chroot) 的示例：

local_root=/var/www/google_feeds

Answer

@djangofan 我不知道 SSHD ftp 子系统是否允许将用户 chrooting 到特定目录...但也许...

@Peter - 尝试查看 /var/log/vsftpd.log 并查看当用户尝试在其 chrooted 目录（/var/www/html）内创建目录时会发生什么 - 它应该记录一些内容，权限、无效响应、无法获取目录列表等。此外，尝试将您的 FTP 客户端设置为PASSIVE模式，这似乎可以解决很多与 FTP 相关的问题。

另外，我希望您正在 chroot 用户，而不是授予完整的系统 FTP 访问权限……这非常危险，您可能有一天会后悔（FTP 极其不安全，默认情况下通过纯文本发送凭据 - 如果您启用 SSL 包装器，那么它会更安全，但仍然拥有完整的系统 FTP 访问权限并不好）。如果您确实需要完整的系统访问权限，并且需要本机权限设置和易用性，请签出 SCP 登录，它使用 SSH（安全）登录，并且用户仅限于您在文件系统中设置的任何权限（与 /etc/passwd 中的用户相同）。

我之前在设置 vsftpd 时遇到过问题（这可能很棘手）...

下面是我的工作系统中将用户 chroot 到目录结构的示例配置：

# Example config file /etc/vsftpd/vsftpd.conf
#
# The default compiled in settings are fairly paranoid. This sample file
# loosens things up a bit, to make the ftp daemon more usable.
# Please see vsftpd.conf.5 for all compiled in defaults.
#
# READ THIS: This example file is NOT an exhaustive list of vsftpd options.
# Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's
# capabilities.
#
# Allow anonymous FTP? (Beware - allowed by default if you comment this out).anonymous_enable=NO
#
# Uncomment this to allow local users to log in.
local_enable=YES
local_root=/var/www
#
# Uncomment this to enable any form of FTP write command.
write_enable=YES
#
# Default umask for local users is 077. You may wish to change this to 022,
# if your users expect that (022 is used by most other ftpd's)
local_umask=022
#
# Uncomment this to allow the anonymous FTP user to upload files. This only
# has an effect if the above global write enable is activated. Also, you will
# obviously need to create a directory writable by the FTP user.
#anon_upload_enable=YES
#
# Uncomment this if you want the anonymous FTP user to be able to create
# new directories.
#anon_mkdir_write_enable=YES
#
# Activate directory messages - messages given to remote users when they
# go into a certain directory.
dirmessage_enable=YES
#
# Activate logging of uploads/downloads.
# The target log file can be vsftpd_log_file or xferlog_file.
# This depends on setting xferlog_std_format parameter
xferlog_enable=YES
#
# Make sure PORT transfer connections originate from port 20 (ftp-data).
connect_from_port_20=YES
#
# If you want, you can arrange for uploaded anonymous files to be owned by
# a different user. Note! Using "root" for uploaded files is not
# recommended!
#chown_uploads=YES
#chown_username=whoever
#
# The name of log file when xferlog_enable=YES and xferlog_std_format=YES
# WARNING - changing this filename affects /etc/logrotate.d/vsftpd.log
#xferlog_file=/var/log/xferlog
#
# Switches between logging into vsftpd_log_file and xferlog_file files.
# NO writes to vsftpd_log_file, YES to xferlog_file
xferlog_std_format=NO
#
# You may change the default value for timing out an idle session.
#idle_session_timeout=600
#
# You may change the default value for timing out a data connection.
#data_connection_timeout=120
#
# It is recommended that you define on your system a unique user which the
# ftp server can use as a totally isolated and unprivileged user.
#nopriv_user=ftpsecure
#
# Enable this and the server will recognise asynchronous ABOR requests. Not
# recommended for security (the code is non-trivial). Not enabling it,
# however, may confuse older FTP clients.
#async_abor_enable=YES
#
# By default the server will pretend to allow ASCII mode but in fact ignore
# the request. Turn on the below options to have the server actually do ASCII
# mangling on files when in ASCII mode.
# Beware that turning on ascii_download_enable enables malicious remote parties
# to consume your I/O resources, by issuing the command "SIZE /big/file" in
# ASCII mode.
# These ASCII options are split into upload and download because you may wish
# to enable ASCII uploads (to prevent uploaded scripts etc. from breaking),
# without the DoS risk of SIZE and ASCII downloads. ASCII mangling should be
# on the client anyway..
#ascii_upload_enable=YES
#ascii_download_enable=YES
#
# You may fully customise the login banner string:
#ftpd_banner=Welcome to blah FTP service.
#
# You may specify a file of disallowed anonymous e-mail addresses. Apparently
# useful for combatting certain DoS attacks.
#deny_email_enable=YES
# (default follows)
#banned_email_file=/etc/vsftpd.banned_emails
#
# You may specify an explicit list of local users to chroot() to their home
# directory. If chroot_local_user is YES, then this list becomes a list of
# users to NOT chroot().
chroot_local_user=YES
#chroot_list_enable=YES
# (default follows)
#chroot_list_file=/etc/vsftpd.chroot_list
#
# You may activate the "-R" option to the builtin ls. This is disabled by
# default to avoid remote users being able to cause excessive I/O on large
# sites. However, some broken FTP clients such as "ncftp" and "mirror" assume
# the presence of the "-R" option, so there is a strong case for enabling it.
#ls_recurse_enable=YES

pam_service_name=vsftpd
userlist_enable=YES
#enable for standalone mode
listen=YES
tcp_wrappers=YES
user_config_dir=/var/www/users
log_ftp_protocol=YES
check_shell=NO

下面是 user_config_dir (chroot) 的示例：

local_root=/var/www/google_feeds

Question 2

对于任何想要执行此操作的人来说，当您想要同时使用 httpd、vsftpd 和 SELinux 时，您必须允许两个守护进程之一的 anon_write。

您可以使用默认设置ls -laZ /var/www

system_u:object_r:httpd_sys_content_t:s0 /var/www

并允许 ftpd 通过以下方式进行匿名写入

setsebool -P ftpd_anon_write 1

您也可以通过设置 ftp 上下文来逆转此设置

chcon -R -t public_content_rw_t /var/www

并允许 httpd 通过以下方式进行匿名写入

setsebool -P httpd_anon_write 1

我会选择第一个设置（允许 ftpd_anon_write），因为它保留了尽可能多的默认配置。

您可能还想启用以下 selinux 布尔值：

setsebool -P ftpd_use_passive_mode 1

甚至丑陋的“全部规则”

setsebool -P ftpd_full_access 1

Answer