O servidor SFTP falha ao iniciar

O servidor SFTP falha ao iniciar

Estou tendo problemas para fazer o sFTP funcionar enquanto não há problemas com o ssh. Basicamente, estou construindo zlib, openssl e openssh para um processador ARM usando um sistema de arquivos Linux incorporado existente. Depois de procurar ideias, isso parecia um problema comum, mas não fiz nenhum progresso. Só tenho um usuário definido, que é root com senha vazia.

Estou usando o openssh versão 4.7p1 e modifiquei o sshd_config com as seguintes configurações:

PermitRootLogin yes
PermitEmptyPasswords yes
UseDNS yes
UsePrivilegeSeparation no
SyslogFacility AUTH
LogLevel DEBUG3
Subsystem sftp /usr/local/libexec/sftp-server -f AUTH -l DEBUG3

O servidor sftp está localizado em /usr/local/libexec e possui as seguintes permissões:

root@arm:/usr/local/libexec# ls -l
-rwxr-xr-x    1 root     root         65533 Oct  3 22:12 sftp-server
-rwx--x--x    1 root     root        233539 Oct  3 22:12 ssh-keysign

Eu sei que o sftp-server está sendo encontrado (o caminho está definido em sshd_config) porque se eu renomear o executável sftp_server, recebo o seguinte erro:

auth.err sshd[1698]: error: subsystem: cannot stat /usr/local/libexec/sftp-server: No such file or directory                                                        
auth.info sshd[1698]: subsystem request for sftp failed, subsystem not found   

Além disso, os scripts de inicialização de login do alvo são muito simples e consistem em um único arquivo (etc/profile.d/local.sh), que contém apenas definições para LD_LIBRARY_PATH, PATH e PYTHONPATH conforme mostrado abaixo:

#!/bin/sh
export LD_LIBRARY_PATH="/usr/local/lib"
export PATH="/usr/local/bin:/usr/local/libexec:${PATH}"
export PYTHONPATH="/home/root/python"

Como você pode ver, .bashrc, .profile, etc não existem no diretório inicial do root:

root@arm:~# ls -la                                                                                                                                                                      
drwxr-xr-x    2 root     root          4096 Oct  4 14:57 .                                                                                                                                    
drwxr-xr-x    3 root     root          4096 Oct  4 01:11 ..                                                                                                                                   
-rw-------    1 root     root           120 Oct  4 01:21 .bash_history

Aqui está a saída do log do sistema ao usar o FileZilla para conectar-se ao servidor sftp no destino. No log, parece que o executável do servidor sftp foi encontrado, mas os processos filhos foram encerrados imediatamente. Estou usando argumentos de depuração ao chamar sftp-server em sshd_config (Subsistema sftp /usr/local/libexec/sftp-server -f AUTH -l DEBUG3), mas nenhum log foi capturado.

Oct  4 14:29:45 arm auth.info sshd[2070]: Connection from 192.168.1.12 port 45888                                                                                                       
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: Client protocol version 2.0; client software version PuTTY_Local:_Mar_28_2012_12:33:05                                               
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: no match: PuTTY_Local:_Mar_28_2012_12:33:05                                                                                          
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: Enabling compatibility mode for protocol 2.0                                                                                         
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: Local version string SSH-2.0-OpenSSH_4.7                                                                                             
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: fd 3 setting O_NONBLOCK                                                                                                              
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: list_hostkey_types: ssh-rsa,ssh-dss                                                                                                  
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: SSH2_MSG_KEXINIT sent                                                                                                                
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: SSH2_MSG_KEXINIT received                                                                                                            
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellma1
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: ssh-rsa,ssh-dss                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysr
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@lysr
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96         
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96         
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: none,[email protected]                                                                                             
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: none,[email protected]                                                                                             
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit:                                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit:                                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: first_kex_follows 0                                                                                               
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: reserved 0                                                                                                        
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellma1
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: ssh-rsa,ssh-dss                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: aes256-ctr,aes256-cbc,[email protected],aes192-ctr,aes192-cbc,aes128-ctr,aes128-cbc,blowfish-ctr,blowfi8
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: aes256-ctr,aes256-cbc,[email protected],aes192-ctr,aes192-cbc,aes128-ctr,aes128-cbc,blowfish-ctr,blowfi8
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: hmac-sha1,hmac-sha1-96,hmac-md5                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: hmac-sha1,hmac-sha1-96,hmac-md5                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: none,zlib                                                                                                         
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: none,zlib                                                                                                         
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit:                                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit:                                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: first_kex_follows 0                                                                                               
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_parse_kexinit: reserved 0                                                                                                        
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: mac_setup: found hmac-sha1                                                                                                           
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: kex: client->server aes256-ctr hmac-sha1 none                                                                                        
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: mac_setup: found hmac-sha1                                                                                                           
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: kex: server->client aes256-ctr hmac-sha1 none                                                                                        
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received                                                                                             
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent                                                                                                       
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: dh_gen_key: priv key bits set: 277/512                                                                                               
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: bits set: 2052/4096                                                                                                                  
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: bits set: 2036/4096                                                                                                                  
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent                                                                                                       
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: kex_derive_keys                                                                                                                      
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: set_newkeys: mode 1                                                                                                                  
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug2: cipher_init: set keylen (16 -> 32)                                                                                                   
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: SSH2_MSG_NEWKEYS sent                                                                                                                
Oct  4 14:29:45 arm auth.debug sshd[2070]: debug1: expecting SSH2_MSG_NEWKEYS                                                                                                           
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: set_newkeys: mode 0                                                                                                                  
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: cipher_init: set keylen (16 -> 32)                                                                                                   
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: SSH2_MSG_NEWKEYS received                                                                                                            
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: KEX done                                                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: userauth-request for user root service ssh-connection method none                                                                    
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: attempt 0 failures 0                                                                                                                 
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug3: Trying to reverse map address 192.168.1.12.                                                                                          
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: parse_server_config: config reprocess config len 302                                                                                 
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: input_userauth_request: setting up authctxt for root                                                                                 
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: input_userauth_request: try method none                                                                                              
Oct  4 14:29:46 arm auth.info sshd[2070]: Accepted none for root from 192.168.1.12 port 45888 ssh2                                                                                      
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: Entering interactive session for SSH2.                                                                                               
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: fd 4 setting O_NONBLOCK                                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: fd 5 setting O_NONBLOCK                                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: server_init_dispatch_20                                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: server_input_channel_open: ctype session rchan 256 win 2147483647 max 16384                                                          
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: input_session_request                                                                                                                
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: channel 0: new [server-session]                                                                                                      
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_new: init                                                                                                                    
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_new: session 0                                                                                                               
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_open: channel 0                                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_open: session 0: link with channel 0                                                                                         
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: server_input_channel_open: confirm session                                                                                           
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: server_input_channel_req: channel 0 request [email protected] reply 0                                               
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_by_channel: session 0 channel 0                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_input_channel_req: session 0 req [email protected]                                                          
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: server_input_channel_req: channel 0 request subsystem reply 1                                                                        
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_by_channel: session 0 channel 0                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_input_channel_req: session 0 req subsystem                                                                                   
Oct  4 14:29:46 arm auth.info sshd[2070]: subsystem request for sftp                                                                                                                    
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: subsystem: exec() /usr/local/libexec/sftp-server -f AUTH -l DEBUG3                                                                   
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: fd 3 setting TCP_NODELAY                                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: fd 7 setting O_NONBLOCK                                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug3: fd 7 is O_NONBLOCK                                                                                                                   
Oct  4 14:29:46 arm auth.debug sshd[2073]: debug1: permanently_set_uid: 0/0                                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2073]: debug3: channel 0: close_fds r -1 w -1 e -1 c -1                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: read<=0 rfd 7 len -1                                                                                                      
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: read failed                                                                                                               
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: close_read                                                                                                                
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: input open -> drain                                                                                                       
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: ibuf empty                                                                                                                
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: send eof                                                                                                                  
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: input drain -> closed                                                                                                     
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: notify_done: reading                                                                                                                 
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: Received SIGCHLD.                                                                                                                    
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_by_pid: pid 2073                                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_exit_message: session 0 channel 0 pid 2073                                                                                   
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: request exit-status confirm 0                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_exit_message: release channel 0                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: write failed                                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: close_write                                                                                                               
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: output open -> closed                                                                                                     
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: send close                                                                                                                
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug3: channel 0: will not send data after close                                                                                            
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: rcvd close                                                                                                                
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug3: channel 0: will not send data after close                                                                                            
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: is dead                                                                                                                   
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: gc: notify user                                                                                                           
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_by_channel: session 0 channel 0                                                                                              
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_close_by_channel: channel 0 child 0                                                                                          
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: session_close: session 0 pid 0                                                                                                       
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: gc: user detached                                                                                                         
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: is dead                                                                                                                   
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug2: channel 0: garbage collecting                                                                                                        
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: channel 0: free: server-session, nchannels 1                                                                                         
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug3: channel 0: status: The following connections are open:\r\n  #0 server-session (t4 r256 i3/0 o3/0 fd 7/7 cfd -1)\r\n                  
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug3: channel 0: close_fds r 7 w 7 e -1 c -1                                                                                               
Oct  4 14:29:46 arm auth.info sshd[2070]: Connection closed by 192.168.1.12                                                                                                             
Oct  4 14:29:46 arm auth.debug sshd[2070]: debug1: do_cleanup                                                                                                                           
Oct  4 14:29:46 arm auth.info sshd[2070]: Closing connection to 192.168.1.12 

Responder1

Embora esta seja mais uma solução alternativa do que uma resposta direta ao seu problema, eu tentaria usar o servidor SFTP interno em vez de um externo. Como este é um sistema embarcado, provavelmente faz mais sentido fazer isso de qualquer maneira.

No seu sshd_config, basta adicionar:

Subsystem sftp internal-sftp

Dessa forma, você pode deixar de fora o binário sftp e economizar espaço.

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