[PATCH] sftpserver: Support some openssh extensions

[Chris Townsend <Christopher.Townsend@xxxxxxxxxxxxx>]

Hi Jakub,

This only allows the libssh sftp server to receive the extended messages
from a client.  The libssh sftp server does not implement any of the
actual command handling on a host and is left up to the developer using
the API on how to do that.

Regards,
Chris

On 08/28/2018 03:56 AM, Jakub Jelen wrote:
> Does this actually implement the the extensions or just sends and
> receives the extended messages?
>
> I don't know a lot about SFTP, but there is nothing referencing the
> rename nor to hardlink in the attached patch.
>
> Jakub
>
>
> On Mon, 2018-08-27 at 10:45 -0500, Alberto Aguirre wrote:
>> From: Chris Townsend <christopher.townsend@xxxxxxxxxxxxx>
>>
>> Add support for "hardlink@xxxxxxxxxxx" and
>> "posix-rename@xxxxxxxxxxx" extensions.
>>
>> Signed-off-by: Alberto Aguirre <albaguirre@xxxxxxxxx>
>> ---
>>  include/libssh/sftp.h |  3 +++
>>  src/sftp.c            |  7 ++++++-
>>  src/sftpserver.c      | 28 ++++++++++++++++++++++++++++
>>  3 files changed, 37 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/libssh/sftp.h b/include/libssh/sftp.h
>> index b07f269f..aac7af2b 100644
>> --- a/include/libssh/sftp.h
>> +++ b/include/libssh/sftp.h
>> @@ -123,6 +123,7 @@ struct sftp_client_message_struct {
>>      sftp_session sftp;
>>      uint8_t type;
>>      uint32_t id;
>> +    char *submessage; /* for extended messages */
>>      char *filename; /* can be "path" */
>>      uint32_t flags;
>>      sftp_attributes attr;
>> @@ -862,6 +863,7 @@ LIBSSH_API const char
>> *sftp_client_message_get_filename(sftp_client_message msg)
>>  LIBSSH_API void sftp_client_message_set_filename(sftp_client_message
>> msg, const char *newname);
>>  LIBSSH_API const char
>> *sftp_client_message_get_data(sftp_client_message msg);
>>  LIBSSH_API uint32_t
>> sftp_client_message_get_flags(sftp_client_message msg);
>> +LIBSSH_API const char
>> *sftp_client_message_get_submessage(sftp_client_message msg);
>>  LIBSSH_API int sftp_send_client_message(sftp_session sftp,
>> sftp_client_message msg);
>>  LIBSSH_API int sftp_reply_name(sftp_client_message msg, const char
>> *name,
>>      sftp_attributes attr);
>> @@ -1011,6 +1013,7 @@ LIBSSH_API void sftp_handle_remove(sftp_session
>> sftp, void *handle);
>>  #define SFTP_RENAME SSH_FXP_RENAME
>>  #define SFTP_READLINK SSH_FXP_READLINK
>>  #define SFTP_SYMLINK SSH_FXP_SYMLINK
>> +#define SFTP_EXTENDED SSH_FXP_EXTENDED
>>  
>>  /* openssh flags */
>>  #define SSH_FXE_STATVFS_ST_RDONLY 0x1 /* read-only */
>> diff --git a/src/sftp.c b/src/sftp.c
>> index 87b6ff94..82b71578 100644
>> --- a/src/sftp.c
>> +++ b/src/sftp.c
>> @@ -219,7 +219,12 @@ int sftp_server_init(sftp_session sftp){
>>      return -1;
>>    }
>>  
>> -  if (ssh_buffer_add_u32(reply, ntohl(LIBSFTP_VERSION)) < 0) {
>> +  if (ssh_buffer_pack(reply, "dssss",
>> +                      ntohl(LIBSFTP_VERSION),
>> +                      "posix-rename@xxxxxxxxxxx",
>> +                      "1",
>> +                      "hardlink@xxxxxxxxxxx",
>> +                      "1") < 0) {
>>      ssh_set_error_oom(session);
>>      ssh_buffer_free(reply);
>>      return -1;
>> diff --git a/src/sftpserver.c b/src/sftpserver.c
>> index 68fdb3d2..3cb30090 100644
>> --- a/src/sftpserver.c
>> +++ b/src/sftpserver.c
>> @@ -202,6 +202,29 @@ sftp_client_message
>> sftp_get_client_message(sftp_session sftp) {
>>          return NULL;
>>        }
>>        break;
>> +    case SSH_FXP_EXTENDED:
>> +      rc = ssh_buffer_unpack(payload,
>> +                             "s",
>> +                             &msg->submessage);
>> +      if (rc != SSH_OK) {
>> +        ssh_set_error_oom(session);
>> +        sftp_client_message_free(msg);
>> +        return NULL;
>> +      }
>> +
>> +      if (strcmp(msg->submessage, "hardlink@xxxxxxxxxxx") == 0 ||
>> +          strcmp(msg->submessage, "posix-rename@xxxxxxxxxxx") == 0)
>> {
>> +        rc = ssh_buffer_unpack(payload,
>> +                               "sS",
>> +                               &msg->filename,
>> +                               &msg->data);
>> +        if (rc != SSH_OK) {
>> +          ssh_set_error_oom(session);
>> +          sftp_client_message_free(msg);
>> +          return NULL;
>> +        }
>> +      }
>> +      break;
>>      default:
>>        ssh_set_error(sftp->session, SSH_FATAL,
>>                      "Received unhandled sftp message %d", msg-
>>> type);
>> @@ -242,12 +265,17 @@ uint32_t
>> sftp_client_message_get_flags(sftp_client_message msg){
>>  	return msg->flags;
>>  }
>>  
>> +const char *sftp_client_message_get_submessage(sftp_client_message
>> msg){
>> +        return msg->submessage;
>> +}
>> +
>>  void sftp_client_message_free(sftp_client_message msg) {
>>    if (msg == NULL) {
>>      return;
>>    }
>>  
>>    SAFE_FREE(msg->filename);
>> +  SAFE_FREE(msg->submessage);
>>    ssh_string_free(msg->data);
>>    ssh_string_free(msg->handle);
>>    sftp_attributes_free(msg->attr);