File Transfer (FTP / FTPS / SFTP / SCP)

duck_net provides functions for transferring files over FTP, FTPS, and SFTP, plus SCP for SSH-based file copy.

Functions

FTP / FTPS

Function	Parameters	Returns
ftp_read	(url)	STRUCT(success, content, size, message)
ftp_read_blob	(url)	STRUCT(success, data BLOB, size, message)
ftp_write	(url, content)	STRUCT(success, bytes_written, message)
ftp_delete	(url)	STRUCT(success, message)
ftp_list	(url)	Table: name, size, is_dir

SFTP

Function	Parameters	Returns
sftp_read	(host, user, key_file, path) or (host, port, user, key_file, path)	STRUCT(success, content, size, message)
sftp_read_blob	(host, user, key_file, path) or (host, port, user, key_file, path)	STRUCT(success, data BLOB, size, message)
sftp_write	(host, user, key_file, path, content)	STRUCT(success, bytes_written, message)
sftp_delete	(host, user, key_file, path)	STRUCT(success, message)
sftp_list	(host, user, key_file, path) with named params	Table: name, size, is_dir

SCP

Function	Parameters	Returns
scp_read	(host, user, key_file, remote_path) or with port	STRUCT(success, data, size, message)
scp_read_password	(host, user, password, remote_path)	STRUCT(success, data, size, message)
scp_write	(host, user, key_file, remote_path, data)	STRUCT(success, bytes_written, message)
scp_write_password	(host, user, password, remote_path, data)	STRUCT(success, bytes_written, message)

FTP Examples

-- Read a text file via FTP
SELECT (ftp_read('ftp://ftp.example.com/pub/data.csv')).content;

-- Read binary data
SELECT (ftp_read_blob('ftp://ftp.example.com/pub/image.png')).data;

-- Upload a file
SELECT (ftp_write('ftp://user:pass@ftp.example.com/upload/data.csv', 'col1,col2\n1,2')).success;

-- List directory contents
FROM ftp_list('ftp://ftp.example.com/pub/');

-- Delete a file
SELECT (ftp_delete('ftp://user:pass@ftp.example.com/upload/old.csv')).success;

SFTP Examples

-- Read a file over SFTP
SELECT (sftp_read('server.example.com', 'deploy', '/home/deploy/.ssh/id_ed25519', '/var/data/report.csv')).content;

-- Read with explicit port
SELECT (sftp_read('server.example.com', 2222, 'deploy', '/home/deploy/.ssh/id_ed25519', '/var/data/report.csv')).content;

-- Write a file
SELECT (sftp_write('server.example.com', 'deploy', '/home/deploy/.ssh/id_ed25519', '/tmp/output.txt', 'Hello!')).success;

-- List remote directory
FROM sftp_list('server.example.com', 'deploy', '/home/deploy/.ssh/id_ed25519', '/var/data/');

SCP Examples

-- Read via SCP with key
SELECT (scp_read('server.example.com', 'deploy', '/home/deploy/.ssh/id_ed25519', '/etc/hostname')).data;

-- Write via SCP with password
SELECT (scp_write_password('server.example.com', 'admin', 'password', '/tmp/config.txt', 'key=value')).success;

Security Considerations

• Path traversal (.., null bytes, excessively long paths) is blocked (CWE-22).
• FTP/SFTP responses are capped at 256 MiB.
• Use FTPS (ftps://) or SFTP instead of plaintext FTP where possible.
• SSH host key verification uses TOFU (Trust On First Use) via known_hosts.
• Store credentials using the secrets manager with ftp or sftp types.
• All hostnames are validated against SSRF rules.