The SSH helper functions

Collaboration diagram for The SSH helper functions:

Macros
#define	NSS_BUFLEN_PASSWD   4096
#define	CLOCK   CLOCK_REALTIME

Functions
int	ssh_getpass (const char *prompt, char *buf, size_t len, int echo, int verify)
	Get a password from the console.
int	ssh_get_random (void *where, int len, int strong)
	Get random bytes.
char *	ssh_get_user_home_dir (void)
int	ssh_file_readaccess_ok (const char *file)
int	ssh_dir_writeable (const char *path)
	Check if the given path is an existing directory and that is accessible for writing.
char *	ssh_get_local_username (void)
int	ssh_is_ipaddr_v4 (const char *str)
int	ssh_is_ipaddr (const char *str)
char *	ssh_lowercase (const char *str)
char *	ssh_hostport (const char *host, int port)
char *	ssh_get_hexa (const unsigned char *what, size_t len)
	Convert a buffer into a colon separated hex string. The caller has to free the memory.
void	ssh_print_hexa (const char *descr, const unsigned char *what, size_t len)
void	ssh_log_hexdump (const char *descr, const unsigned char *what, size_t len)
	Log the content of a buffer in hexadecimal format, similar to the output of 'hexdump -C' command.
const char *	ssh_version (int req_version)
	Check if libssh is the required version or get the version string.
struct ssh_list *	ssh_list_new (void)
void	ssh_list_free (struct ssh_list *list)
struct ssh_iterator *	ssh_list_get_iterator (const struct ssh_list *list)
struct ssh_iterator *	ssh_list_find (const struct ssh_list *list, void *value)
size_t	ssh_list_count (const struct ssh_list *list)
	Get the number of elements in the list.
int	ssh_list_append (struct ssh_list *list, const void *data)
int	ssh_list_prepend (struct ssh_list *list, const void *data)
void	ssh_list_remove (struct ssh_list *list, struct ssh_iterator *iterator)
const void *	_ssh_list_pop_head (struct ssh_list *list)
char *	ssh_dirname (const char *path)
	Parse directory component.
char *	ssh_basename (const char *path)
	basename - parse filename component.
int	ssh_mkdir (const char *pathname, mode_t mode)
	Attempts to create a directory with the given pathname.
int	ssh_mkdirs (const char *pathname, mode_t mode)
	Attempts to create a directory with the given pathname. The missing directories in the given pathname are created recursively.
char *	ssh_path_expand_tilde (const char *d)
	Expand a directory starting with a tilde '~'.
char *	ssh_path_expand_escape (ssh_session session, const char *s)
int	ssh_analyze_banner (ssh_session session, int server)
void	ssh_timestamp_init (struct ssh_timestamp *ts)
int	ssh_make_milliseconds (unsigned long sec, unsigned long usec)
int	ssh_timeout_elapsed (struct ssh_timestamp *ts, int timeout)
int	ssh_timeout_update (struct ssh_timestamp *ts, int timeout)
	updates a timeout value so it reflects the remaining time
int	ssh_match_group (const char *group, const char *object)
void	explicit_bzero (void *s, size_t n)
char *	strndup (const char *s, size_t n)
void	uint64_inc (unsigned char *counter)
int	ssh_quote_file_name (const char *file_name, char *buf, size_t buf_len)
int	ssh_newline_vis (const char *string, char *buf, size_t buf_len)
int	ssh_tmpname (char *name)
char *	ssh_strreplace (const char *src, const char *pattern, const char *replace)
char *	ssh_strerror (int err_num, char *buf, size_t buflen)
int	ssh_check_hostname_syntax (const char *hostname)
	Checks syntax of a domain name.

Detailed Description

Different helper functions used in the SSH Library.

Function Documentation

ssh_basename()

char * ssh_basename

(

const char *

path

)

basename - parse filename component.

basename breaks a null-terminated pathname string into a filename component. ssh_basename() returns the component following the final '/'. Trailing '/' characters are not counted as part of the pathname.

Parameters

[in]

path

The path to parse.

Returns

The filename of path or NULL if we can't allocate memory. If path is the string "/", basename returns the string "/". If path is NULL or an empty string, "." is returned. The caller needs to free this memory ssh_string_free_char().

See also

ssh_string_free_char()

ssh_check_hostname_syntax()

int ssh_check_hostname_syntax

(

const char *

hostname

)

Checks syntax of a domain name.

The check is made based on the RFC1035 section 2.3.1 Allowed characters are: hyphen, period, digits (0-9) and letters (a-zA-Z)

The label should be no longer than 63 characters The label should start with a letter and end with a letter or number The label in this implementation can start with a number to allow virtual URLs to pass. Note that this will make IPv4 addresses to pass this check too.

Parameters

hostname

The domain name to be checked, has to be null terminated

Returns

SSH_OK if the hostname passes syntax check SSH_ERROR otherwise or if hostname is NULL or empty string

ssh_dir_writeable()

int ssh_dir_writeable

(

const char *

path

)

Check if the given path is an existing directory and that is accessible for writing.

Parameters

[in]

path

Path to the directory to be checked

Returns

Return 1 if the directory exists and is accessible; 0 otherwise

ssh_dirname()

char * ssh_dirname

(

const char *

path

)

Parse directory component.

dirname breaks a null-terminated pathname string into a directory component. In the usual case, ssh_dirname() returns the string up to, but not including, the final '/'. Trailing '/' characters are not counted as part of the pathname. The caller must free the memory using ssh_string_free_char().

Parameters

[in]

path

The path to parse.

Returns

The dirname of path or NULL if we can't allocate memory. If path does not contain a slash, c_dirname() returns the string ".". If path is a string "/", it returns the string "/". If path is NULL or an empty string, "." is returned. The memory needs to be freed using ssh_string_free_char().

See also

ssh_string_free_char()

ssh_get_hexa()

char * ssh_get_hexa	(	const unsigned char *	what,
		size_t	len )

Convert a buffer into a colon separated hex string. The caller has to free the memory.

Parameters

[in]	what	What should be converted to a hex string.
[in]	len	Length of the buffer to convert.

Returns

The hex string or NULL on error. The memory needs to be freed using ssh_string_free_char().

See also

ssh_string_free_char()

ssh_get_random()

int ssh_get_random	(	void *	where,
		int	len,
		int	strong )

Get random bytes.

Make sure to always check the return code of this function!

Parameters

[in]	where	The buffer to fill with random bytes
[in]	len	The size of the buffer to fill.
[in]	strong	Use a strong or private RNG source.

Returns

1 on success, 0 on error.

ssh_getpass()

int ssh_getpass	(	const char *	prompt,
		char *	buf,
		size_t	len,
		int	echo,
		int	verify )

Get a password from the console.

You should make sure that the buffer is an empty string!

You can also use this function to ask for a username. Then you can fill the buffer with the username and it is shows to the users. If the users just presses enter the buffer will be untouched.

char username[128];
 
snprintf(username, sizeof(username), "john");
 
ssh_getpass("Username:", username, sizeof(username), 1, 0);

The prompt will look like this:

Username: [john]

If you press enter then john is used as the username, or you can type it in to change it.

Parameters

[in]	prompt	The prompt to show to ask for the password.
[out]	buf	The buffer the password should be stored. It NEEDS to be empty or filled out.
[in]	len	The length of the buffer.
[in]	echo	Should we echo what you type.
[in]	verify	Should we ask for the password twice.

Returns

0 on success, -1 on error.

ssh_list_count()

size_t ssh_list_count

(

const struct ssh_list *

list

)

Get the number of elements in the list.

Parameters

[in]

list

The list to count.

Returns

The number of elements in the list.

ssh_log_hexdump()

void ssh_log_hexdump	(	const char *	descr,
		const unsigned char *	what,
		size_t	len )

Log the content of a buffer in hexadecimal format, similar to the output of 'hexdump -C' command.

The first logged line is the given description followed by the length. Then the content of the buffer is logged 16 bytes per line in the following format:

(offset) (first 8 bytes) (last 8 bytes) (the 16 bytes as ASCII char values)

The output for a 16 bytes array containing values from 0x00 to 0x0f would be:

"Example (16 bytes):" " 00000000 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f ................"

The value for each byte as corresponding ASCII character is printed at the end if the value is printable. Otherwise, it is replaced with '.'.

Parameters

[in]	descr	A description for the content to be logged
[in]	what	The buffer to be logged
[in]	len	The length of the buffer given in what

Note

If a too long description is provided (which would result in a first line longer than 80 bytes), the function will fail.

ssh_mkdir()

int ssh_mkdir	(	const char *	pathname,
		mode_t	mode )

Attempts to create a directory with the given pathname.

This is the portable version of mkdir, mode is ignored on Windows systems.

Parameters

[in]	pathname	The path name to create the directory.
[in]	mode	The permissions to use.

Returns

0 on success, < 0 on error with errno set.

ssh_mkdirs()

int ssh_mkdirs	(	const char *	pathname,
		mode_t	mode )

Attempts to create a directory with the given pathname. The missing directories in the given pathname are created recursively.

Parameters

[in]	pathname	The path name to create the directory.
[in]	mode	The permissions to use.

Returns

0 on success, < 0 on error with errno set.

Note

mode is ignored on Windows systems.

ssh_path_expand_tilde()

char * ssh_path_expand_tilde

(

const char *

d

)

Expand a directory starting with a tilde '~'.

Parameters

[in]

d

The directory to expand.

Returns

The expanded directory, NULL on error. The caller needs to free the memory using ssh_string_free_char().

See also

ssh_string_free_char()

ssh_print_hexa()

void ssh_print_hexa	(	const char *	descr,
		const unsigned char *	what,
		size_t	len )

Deprecated

Please use ssh_print_hash() instead

ssh_timeout_update()

int ssh_timeout_update	(	struct ssh_timestamp *	ts,
		int	timeout )

updates a timeout value so it reflects the remaining time

Parameters

[in]	ts	pointer to an existing timestamp
[in]	timeout	timeout in milliseconds. Negative values mean infinite timeout

Returns

remaining time in milliseconds, 0 if elapsed, -1 if never.

ssh_version()

const char * ssh_version

(

int

req_version

)

Check if libssh is the required version or get the version string.

Parameters

[in]

req_version

The version required.

Returns

If the version of libssh is newer than the version required it will return a version string. NULL if the version is older.

Example:

if (ssh_version(SSH_VERSION_INT(0,2,1)) == NULL) {
  fprintf(stderr, "libssh version is too old!\n");
  exit(1);
}
 
if (debug) {
  printf("libssh %s\n", ssh_version(0));
}