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SKEYLOOKUP(3) Library Functions Manual SKEYLOOKUP(3)

atob8, backspace, btoa8, btoe, etob, f, htoi, keycrunch, put8, readpass, readskey, rip, sevenbit, skey_authenticate, skey_get_algorithm, skey_haskey, skey_keyinfo, skey_passcheck, skey_set_algorithm, skey_unlock, skeychallenge, skeychallenge2, skeygetnext, skeylookup, skeyverify, skipspace
S/Key library functions

#include <skey.h>
int
atob8(char *out, char *in);
void
backspace(char *buf);
int
btoa8(char *out, char *in);
char *
btoe(char *engout, char *c);
int
etob(char *out, char *e);
void
f(char *x);
int
htoi(int h);
int
keycrunch(char *result, char *seed, char *passwd);
char *
put8(char *out, char *s);
char *
readpass(char *buf, int n);
char *
readskey(char *buf, int n);
void
rip(char *buf);
void
sevenbit(char *s);
int
skey_authenticate(char *user);
const char *
skey_get_algorithm(void);
int
skey_haskey(char *user);
char *
skey_keyinfo(char *user);
int
skey_passcheck(char *user, char *passwd);
char *
skey_set_algorithm(char *new);
int
skey_unlock(struct skey *rec);
int
skeychallenge(struct skey *rec, char *user, char *buf);
int
skeychallenge2(int fd, struct skey *rec, char *user, char *buf);
int
skeygetnext(struct skey *rec);
int
skeylookup(struct skey *rec, char *user);
int
skeyverify(struct skey *rec, char *response);
char *
skipspace(char *);

These functions implement the S/Key one time password authentication mechanism.
The atob8() function converts the 16-byte hex string in to an 8-byte binary array stored in out. The atob8() function returns 0 on success and -1 if an invalid hex character is encountered.
The backspace() function removes backspaced over characters from buf. Note that backspace() assumes the actual backspace character is 0x8 (^H).
The btoa8() function converts the 8-byte binary array in to a 16-byte string of hex digits stored in out; the caller must supply enough space (17 bytes including the final NUL). The btoa8() function returns 0 on success and -1 if an error occurred.
The btoe() function encodes the 8 bytes in c into a string of 6 English words, stored in engout. The caller must supply enough space (30 bytes including the final NUL) to store the words. The btoe() function returns engout.
The etob() function converts the 6 English words in e into an 8-byte binary representation. The etob() function returns 1 if the words are all in the database and parity is correct, 0 if a word is not in the database, -1 if the number of words is incorrect, or -2 if there is a parity error.
The f() function is a one-way hash that overwrites the 8-byte input buffer x with the hashed result.
The htoi() function converts a single hex digit h to an integer. The htoi() function returns the converted integer on success or -1 if h not a valid hex digit.
The keycrunch() function concatenates the seed and passwd, runs them through a hash function and collapses the result to 64 bits. The keycrunch() function returns 0 on success or -1 if there is a memory allocation failure.
The put8() function converts the 8 bytes stored in s into a series of 4 16-bit hex digit stored in out. There must be at least 20 bytes (including the NUL) in the output buffer, out. The put8() function returns out.
The readpass() function reads up to n characters from standard input with echo turned off, converting the resulting string to 7 bits, storing the result in buf. The readpass() function returns buf.
The readskey() function reads up to n characters from standard input with echo turned on, converting the resulting string to 7 bits, storing the result in buf. The readskey() function returns buf.
The rip() function strips trailing linefeeds and carriage returns from buf.
The sevenbit() function strips the high bit from each character in s, converting the characters to seven bit ASCII.
The skey_authenticate() function presents the user with an S/Key challenge and authenticates the response. The skey_authenticate() function returns 0 if authentication is successful or -1 if not.
The skey_get_algorithm() function returns a string corresponding to the hash algorithm for the current user. The default algorithm is “md5”.
The skey_haskey() function returns 0 if the user exists in the S/Key database, 1 if the user does not exist, or -1 if there was an error reading the database.
The skey_keyinfo() function returns a string containing the current sequence number and seed for user. The returned string points to internal static storage that will be overwritten by subsequent calls to skey_keyinfo().
The skey_passcheck() function checks a user and passwd pair against the S/Key database. It returns 0 on successful authentication or -1 on failure.
The skey_set_algorithm() function sets the user's hash algorithm based on the string new. The skey_set_algorithm() function returns the specified algorithm if it is supported, or the null pointer if the hash algorithm is not supported.
The skey_unlock() function unlocks the record in the S/Key database specified by rec. The skey_unlock() function returns 0 on success or -1 on failure. Either way, the S/Key database is not closed nor is the database file pointer affected.
The skeychallenge() function stores the (potentially fake) S/Key challenge for user in buf, which is at least SKEY_MAX_CHALLENGE bytes long. It also fills in the skey struct rec and locks the user's record in the S/Key database. The skeychallenge() function returns 0 on success or -1 on failure. On success the S/Key database remains open and the read/write file pointer is set to the beginning of the record.
The skeychallenge2() function is identical to skeychallenge() except that instead of opening the user's entry in the S/Key database, the open file referenced by fd is used instead. When fd is -1, the behavior is equivalent to skeychallenge().
The skeygetnext() function stores the next record in the S/Key database in rec and locks that record in the S/Key database. The skeygetnext() function returns 0 on success, 1 if there are no more entries, or -1 if there was an error accessing the S/Key database. The S/Key database remains open after a call to skeygetnext(). If no error was encountered accessing the S/Key database, the read/write file pointer is set to the beginning of the record or at EOF if there are no more records.
 
Because it exposes other users' S/Key records, only the superuser may use skeygetnext().
The skeylookup() function looks up the specified user in the S/Key database then fills in the skey struct rec and locks the user's record in the database. The skeylookup() function returns 0 on success, 1 if user was not found, or -1 if there was an error accessing the S/Key database. If no error was encountered accessing the S/Key database, the read/write file pointer is set to the beginning of the record.
The skeyverify() function verifies the user's response based on the S/Key record rec. It returns 0 on success (updating the database), 1 on failure, or -1 if there was an error accessing the database. The database is always closed by a call to skeyverify().

skey(1), skeyinit(1)

There is no standard API for S/Key. The de facto standard is the free S/Key distribution released by Bellcore.
The following functions are extensions and do not appear in the original Bellcore S/Key distribution: readskey(), skey_authenticate(), skey_get_algorithm(), skey_haskey(), skey_keyinfo(), skey_passcheck(), skey_set_algorithm(), skey_unlock().
S/Key is a Trademark of Bellcore.
November 10, 2015 OpenBSD-current