限制ssh登录ip

SSH单用户登录简介

SSH(Secure Shell)是一种网络协议，用于在不安全的网络环境中提供安全的远程登录服务，SSH协议是目前最广泛使用的加密远程登录协议之一，它可以在不安全的网络环境中为用户提供安全的远程登录服务，SSH协议的主要特点包括：数据加密、身份验证、以及传输层安全性。

实现限制SSH单用户登录的方法

1、修改SSH配置文件

限制SSH单用户登录的最直接方法是修改SSH配置文件，通过设置MaxSessions参数来限制单个用户的会话数量，当达到最大会话数时，新用户将无法再进行SSH登录。

操作步骤如下：

(1)打开SSH配置文件：

sudo nano /etc/ssh/sshd_config

(2)在配置文件中找到或添加MaxSessions参数，设置其值为所需的最大会话数，

MaxSessions 10

(3)保存并退出配置文件。

(4)重启SSH服务以使更改生效：

sudo systemctl restart sshd

2、使用PAM(Pluggable Authentication Modules)模块

除了修改SSH配置文件外，还可以使用PAM模块来限制SSH单用户登录，具体操作方法如下：

(1)创建一个新的PAM模块，用于限制单个用户的会话数量，创建一个名为limit_user_login.c的文件，内容如下：

include <security/pam_appl.h>
include <security/pam_misc.h>
include <stdio.h>
include <string.h>
include <syslog.h>
include <unistd.h>
include <arpa/inet.h>
include <netdb.h>
include <pwd.h>
include <time.h>
include <sys/types.h>
include <sys/socket.h>
include <netinet/in.h>
include <fcntl.h>
include <errno.h>
include <stdlib.h>
include <assert.h>
include <locale.h>
include <dirent.h>
include <signal.h>
include <setjmp.h>
include <limits.h>
include <sys/resource.h>
include <sys/stat.h>
include <semaphore.h>
include <gcrypt/crypt-gcrypt.h>
include <gcrypt/openpgp-modules.h>
include <gpgme/error.h>
include <gpgme/ctx.h>
include <gpgme/ctrl_struct.h>
include <gpgme/procmem.h>
include <gpgme/utility.h>
include <gpgme/xmss-params.h>
include "common-utils.h"
define MAX_USER_SESSIONS 1000000 /* max number of sessions for a single user */
static struct pam_conv conv = NULL; /* callback function */
static int limit_user_login_auth(struct pam_message **msg, void *appdata_ptr) { /* authentication function */}
static int limit_user_login_check(struct pam_message **msg, void *appdata_ptr, void *retval) { /* check function */}*/
/*int limit_user_login_init(struct pam_context *pamctx) { */ /* initialization function *//*return PAM_SUCCESS; *//*}*/ /*int limit_user_login_cleanup(struct pam_context *) { return PAM_SUCCESS; }*/ /*const struct pam_module limit_user_login_module = { */ "limit-user-login", /* name */ "Limit User Login", /* authfn */ limit_user_login_auth, /* checkfn */ limit_user_login_check, /* initfn */ NULL, /* cleanupfn */ NULL, /* preauthfn */ NULL, /* postauthfn */ NULL, /* acctinfofn */ NULL, /* getcredfn */ NULL, /* setcredfn */ NULL, /* opensessionfn */ NULL, /* closesessionfn */ NULL, /* auditsessionfn */ NULL, /* eoffn */ NULL};*/ char *getpassphrase() { return NULL; }/*void gpgme_updateenv() { return; }*/ static void *limiter_thread(void *arg) { /* create semaphore */ sem_t *lock = (sem_t *)arg; /* acquire lock */ sem_wait(lock); /* loop until max session count is reached */ while (current_sessions <= MAX_USER_SESSIONS) { /* sleep for a while to avoid busy waiting */ usleep(1000); /* release lock */ sem_post(lock); } /* delete semaphore */ semctl(lock, 0, IPC_RMID); return NULL;}*/ static void limiter(char *username) { /* create semaphore */ sem_t *lock = (sem_t *)malloc(sizeof(sem_t)); if (!lock) return; sem_init(lock, 0, 1); /* create thread to limit sessions for this user */ pthread_create(&threads[username], NULL, limiter_thread, (void *)lock);}/*static void removelimiter(char *username) { free(threads[username]); threads[username] = NULL; semctl(threads[username], 0, IPC_RMID);}*/ int main() { /* initialize OpenPGP library */ gpgme_init(); gpgme_armor_setcapability(GPGME_ARMOR_CAPABILITY_TEXT | GPGME_ARMOR_CAPABILITY_XML | GPGME_ARMOR_CAPABILITY_JSON | GPGME_ARMOR_CAPABILITY_ASCII); gpgme_editdata().opaque = &opaque; gpgme_editdata().format = GPGME_DATAFORMAT_NEW; gpgme_editdata().trustedkeyops = NULL; gpgme_editdata().sigops = NULL; gpgme_editdata().symkeyops = NULL; gpgme_editdata().preferringkeys = NULL; gpgme_editdata().pinentry = NULL; gpgme_editdata().pinblocking = TRUE; gpgme_editdata().decryptionkeyops = NULL; gpgme_editdata().encryptionkeyops = NULL; gpgme_editdata().signingkeyops = NULL; gpgme_editdata().verifyingkeyops = NULL; gpgme_editdata().compressionops = NULL; gpgme_editdata().untrustedkeyops = NULL; gpgme_editdata().dhkeyops = NULL; gpgme_editdata().ecdhkeyops = NULL; gpgme_editdata().engines = NULL; if (!gpgmetetext()) return 1; /* read private key from file and encrypt it with the user's passphrase */ if (!readkeyfile(privatekey)) return 1; if (!decryptkeywithpassphrase()) return 1; if (!importsecretkey()) return 1; if (!writesigneddata()) return 1; if (!writeencrypteddata()) return 1; if (!writesignedandencrypteddata()) return 1; if (!writeclearsignedandencrypteddata()) return 1; if (!writeasciiarmoredsignedandencrypteddata()) return 1; if (!writexmlarmoredsignedandencrypteddata()) return 1; if (!writejsonarmoredsignedandencrypteddata()) return 1; if (!writeplaintextsignedandencrypteddata()) return 1; if (!writeasciiarmoredsignedonlydata()) return 1; if (!writexmlarmoredsignedonlydata()) return 1; if (!writejsonarmoredsignedonlydata()) return 1; if (!writeplaintextsignedonlydata()) return 1; if (!writeasciiarmoredunsignedonlydata()) return 1; if (!writexmlarmoredunsignedonlydata()) return 1; if (!writejsonarmoredunsignedonlydata()) return 1; if (!writeplaintextunsignedonlydata()) return 1; /* initialize OpenPGP library with custom modules */ gpgme --allow-secret-key-import --enable-large-cache=yes --with-gnutls --with-libassuan --with-libgcrypt --with-libexpat --with-libnettle --with-libssh2 --with-libidn