Allow modified key files to be discarded.

[u/mdw/catacomb] / key.h

/* -*-c-*-
 *
 * $Id$
 *
 * Simple key management
 *
 * (c) 1999 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Catacomb.
 *
 * Catacomb is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * Catacomb is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with Catacomb; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#ifndef CATACOMB_KEY_H
#define CATACOMB_KEY_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Header files ------------------------------------------------------*/

#include <stdio.h>
#include <time.h>

#include <mLib/bits.h>
#include <mLib/dstr.h>
#include <mLib/hash.h>
#include <mLib/sym.h>

#ifndef CATACOMB_KEY_DATA_H
#  include "key-data.h"
#endif

#ifndef CATACOMB_GHASH_H
#  include "ghash.h"
#endif

#ifndef CATACOMB_MP_H
#  include "mp.h"
#endif

/*----- Data structures ---------------------------------------------------*/

/* --- Key attributes --- *
 *
 * Each attribute is stored as a symbol in a symbol table.  The value is
 * the plain (not url-encoded) text to be written to the the file.  If the
 * value is binary data, then by this point it's base-64 encoded.
 */

typedef struct key_attr {
  sym_base _b;                          /* Symbol table data */
  char *p;                              /* Pointer to attribute value */
} key_attr;

/* --- Main key structure --- *
 *
 * Each key is stored in two symbol tables, one indexed by keyid, and the
 * other indexed by type.  Because many keys can have the same type, the type
 * table contains a list of keys, sorted in descending order of expiry.
 */

typedef struct key {

  /* --- Hashtable management --- */
  
  hash_base _b;                         /* Symbol table data */
  struct key *next;                     /* Next key of the same type */

  /* --- Basic key attributes --- */

  uint32 id;                            /* Key id used to name it */
  char *tag;                            /* Textual tag name */
  char *type;                           /* Textual key type */
  time_t exp, del;                      /* Expiry times for keys */

  /* --- The key data itself --- */

  key_data k;                           /* The actual key data */

  /* --- Other attributes and commentary --- */

  sym_table a;                          /* Hashtable of key attributes */
  char *c;                              /* Any additional comments */
} key;

/* --- The keys-by-type entries --- */

typedef struct key_ref {
  sym_base _b;                          /* Symbol table data */
  key *k;                               /* Pointer to first key in list */
} key_ref;

/* --- A key file --- */

typedef struct key_file {
  FILE *fp;                             /* File pointer open on file */
  char *name;                           /* Filename used to create it */
  unsigned f;                           /* Various useful flags */
  hash_table byid;                      /* Table of keys by keyid */
  sym_table bytype;                     /* Table of keys by type */
  sym_table bytag;                      /* Table of keys by tag */
  size_t idload;                        /* Loading on id table */
} key_file;

/* --- Key file flags --- */

#define KF_WRITE 1u                     /* File opened for writing */
#define KF_MODIFIED 2u                  /* File has been modified */

/* --- Iterating over keys --- *
 *
 * Both of these are simple symbol table iterators, but they're made distinct
 * types for the dubious benefits that type safety brings.
 */

typedef struct { hash_iter i; time_t t; } key_iter;
typedef struct { sym_iter i; } key_attriter;

/* --- Key fetching --- */

typedef struct key_fetchdef {
  char *name;                           /* Name of item */
  size_t off;                           /* Offset into target structure */
  unsigned e;                           /* Flags for the item */
  const struct key_fetchdef *kf;        /* Substructure pointer */
} key_fetchdef;

/* --- File opening options --- */

#define KOPEN_READ 0u
#define KOPEN_WRITE 1u
#define KOPEN_MASK 0xff
#define KOPEN_NOFILE 0x100

/* --- Various other magic numbers --- */

#define KEXP_FOREVER ((time_t)-1)       /* Never expire this key */
#define KEXP_EXPIRE ((time_t)-2)        /* Expire this key when unused */

/* --- Key error codes --- */

enum {
  KERR_OK = 0,                          /* No error */
  KERR_BADTAG = -1,                     /* Malformed tag string */
  KERR_BADTYPE = -2,                    /* Malformed type string */
  KERR_BADCOMMENT = -3,                 /* Malformed comment string */
  KERR_DUPID = -4,                      /* Duplicate keyid */
  KERR_DUPTAG = -5,                     /* Duplicate key tag string */
  KERR_READONLY = -6,                   /* Key file is read-only */
  KERR_WILLEXPIRE = -7,                 /* Key will eventually expire */
  KERR_EXPIRED = -8,                    /* Key has already expired */
  KERR_BADFLAGS = -9,                   /* Error in flags string */
  KERR_BADPASS = -10,                   /* Error decrypting locked key */
  KERR_WRONGTYPE = -11,                 /* Key has incorrect type */
  KERR_NOTFOUND = -12,                  /* Key couldn't be found */
  KERR_BADATTR = -13,                   /* Malformed attribute name */
  KERR_MAX                              /* Largest possible error */
};

/* --- Write error codes --- */

enum {
  KWRITE_OK,                            /* Everything went fine */
  KWRITE_FAIL = -1,                     /* Close attempt failed */
  KWRITE_BROKEN = -2                    /* Key ring needs manual fixing */
};

/* --- Error reporting functions for @key_merge@ and @key_open@ --- */

typedef void key_reporter(const char */*file*/, int /*line*/,
                          const char */*err*/, void */*p*/);

/* --- Macros for testing expiry --- */

#define KEY_EXPIRED(now, exp)                                           \
  ((exp) == KEXP_EXPIRE || ((exp) != KEXP_FOREVER && (exp) < (now)))

/*----- Reading and writing keys and files --------------------------------*/

/* --- @key_merge@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file structure
 *              @const char *file@ = name of file (for error messages)
 *              @FILE *fp@ = file handle to read from
 *              @key_reporter *rep@ = error reporting function
 *              @void *arg@ = argument for function
 *
 * Returns:     Error code (one of the @KERR@ constants).
 *
 * Use:         Reads keys from a file, and inserts them into the file.
 */

extern int key_merge(key_file */*f*/, const char */*file*/, FILE */*fp*/,
                     key_reporter */*rep*/, void */*arg*/);

/* --- @key_extract@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file structure
 *              @key *k@ = key to extract
 *              @FILE *fp@ = file to write on
 *              @const key_filter *kf@ = pointer to key selection block
 *
 * Returns:     Zero if OK, EOF on error.
 *
 * Use:         Extracts a key to an ouptut file.
 */

extern int key_extract(key_file */*f*/, key */*k*/, FILE */*fp*/,
                       const key_filter */*kf*/);

/* --- @key_open@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file structure to initialize
 *              @const char *file@ = pointer to the file name
 *              @unsigned how@ = opening options (@KOPEN_*@).
 *              @key_reporter *rep@ = error reporting function
 *              @void *arg@ = argument for function
 *
 * Returns:     Zero if it worked, nonzero otherwise.
 *
 * Use:         Opens a key file, reads its contents, and stores them in a
 *              structure.  The file is locked appropriately until closed
 *              using @key_close@.  On an error, everything is cleared away
 *              tidily.  If the file is opened with @KOPEN_WRITE@, it's
 *              created if necessary, with read and write permissions for its
 *              owner only.
 */

extern int key_open(key_file */*f*/, const char */*file*/, unsigned /*how*/,
                    key_reporter */*rep*/, void */*arg*/);

/* --- @key_discard@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to key file block
 *
 * Returns:     ---
 *
 * Use:         Frees all the key data, without writing changes.
 */

extern int key_discard(key_file */*f*/);

/* --- @key_close@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to key file block
 *
 * Returns:     A @KWRITE_@ code indicating how it went.
 *
 * Use:         Frees all the key data, writes any changes.  Make sure that
 *              all hell breaks loose if this returns @KWRITE_BROKEN@.
 */

extern int key_close(key_file */*f*/);

/* --- @key_save@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to key file block
 *
 * Returns:     A @KWRITE_@ code indicating how well it worked.
 *
 * Use:         Writes a key file's data back to the actual file.  This code
 *              is extremely careful about error handling.  It should usually
 *              be able to back out somewhere sensible, but it can tell when
 *              it's got itself into a real pickle and starts leaving well
 *              alone.
 *
 *              Callers, please make sure that you ring alarm bells when this
 *              function returns @KWRITE_BROKEN@.
 */

extern int key_save(key_file */*f*/);

/* --- @key_lockfile@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file structure to initialize
 *              @const char *file@ = pointer to the file name
 *              @unsigned how@ = opening options (@KOPEN_*@).
 *
 * Returns:     Zero if it worked, nonzero otherwise.
 *
 * Use:         Opens a keyfile and stores the information needed for
 *              continued access in the structure.
 *
 *              If the file is opened with @KOPEN_WRITE@, it's created if
 *              necessary with read and write permissions for owner only, and
 *              locked for update while it's open.
 *
 *              This is a system-dependent routine, and only really intended
 *              for the private use of @key_open@.
 */

extern int key_lockfile(key_file */*f*/, const char */*file*/,
                        unsigned /*how*/);

/*----- Creating and manipulating keys ------------------------------------*/

/* --- @key_new@ ---
 *
 * Arguments:   @key_file *f@ = pointer to key file
 *              @uint32 id@ = keyid to set
 *              @const char *type@ = the type of this key
 *              @time_t exp@ = when the key expires
 *              @int *err@ = where to store the error condition
 *
 * Returns:     Key block containing new data, or null if it couldn't be
 *              done.
 *
 * Use:         Attaches a new key to a key file.  You must have a writable
 *              key file for this to work.
 *
 *              The type is a key type string.  This interface doesn't care
 *              about how type strings are formatted: it just treats them as
 *              opaque gobs of text.  Clients are advised to choose some
 *              standard for representing key types, though.
 *
 *              The expiry time should either be a time in the future, or the
 *              magic value @KEXP_FOREVER@ which means `never expire this
 *              key'.  Be careful with `forever' keys.  If I were you, I'd
 *              use a more sophisticated key management system than this for
 *              them.
 *
 *              You have to set the actual key yourself.
 */

extern key *key_new(key_file */*f*/, uint32 /*id*/, const char */*type*/,
                    time_t /*exp*/, int */*err*/);

/* --- @key_delete@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file block
 *              @key *k@ = key to delete
 *
 * Returns:     Error code (one of the @KERR@ constants).
 *
 * Use:         Removes the given key from the list.  The key file must be
 *              writable.  (Due to the horridness of the data structures,
 *              deleted keys aren't actually removed, just marked so that
 *              they can't be looked up or iterated over.  One upshot of
 *              this is that they don't get written back to the file when
 *              it's closed.)
 */

extern int key_delete(key_file */*f*/, key */*k*/);

/* --- @key_expired@ --- *
 *
 * Arguments:   @key *k@ = pointer to key block
 *
 * Returns:     Zero if the key is OK, nonzero if it's expired.
 */

int key_expired(key */*k*/);

/* --- @key_expire@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file block
 *              @key *k@ = pointer to key block
 *
 * Returns:     Error code (one of the @KERR@ constants).
 *
 * Use:         Immediately marks the key as expired.  It may be removed
 *              immediately, if it is no longer required, and will be removed
 *              by a tidy operation when it is no longer required.  The key
 *              file must be writable.
 */

extern int key_expire(key_file */*f*/, key */*k*/);

/* --- @key_used@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to key file
 *              @key *k@ = pointer to key block
 *              @time_t t@ = when key can be removed
 *
 * Returns:     Zero if OK, nonzero on failure.
 *
 * Use:         Marks a key as being required until a given time.  Even
 *              though the key may expire before then (and won't be returned
 *              by type after that time), it will still be available when
 *              requested explicitly by id.  The key file must be writable.
 *
 *              The only (current) reason for failure is attempting to use
 *              a key which can expire for something which can't.
 */

extern int key_used(key_file */*f*/, key */*k*/, time_t /*t*/);

/* --- @key_fingerprint@ --- *
 *
 * Arguments:   @key *k@ = the key to fingerprint
 *              @ghash *h@ = the hash to use
 *              @const key_filter *kf@ = filter to apply
 *
 * Returns:     Nonzero if the key slightly matched the filter.
 *
 * Use:         Updates the hash context with the key contents.
 */

extern int key_fingerprint(key */*k*/, ghash */*h*/,
                           const key_filter */*kf*/);

/*----- Setting and reading attributes ------------------------------------*/

/* --- @key_chkident@ --- *
 *
 * Arguments:   @const char *p@ = pointer to a type string
 *
 * Returns:     Zero if OK, -1 on error.
 *
 * Use:         Checks whether an identification component string is OK.
 */

extern int key_chkident(const char */*p*/);

/* --- @key_chkcomment@ --- *
 *
 * Arguments:   @const char *p@ = pointer to a comment string
 *
 * Returns:     Zero if OK, -1 on error.
 *
 * Use:         Checks whether a comment string is OK.
 */

extern int key_chkcomment(const char */*p*/);

/* --- @key_setcomment@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to key file block
 *              @key *k@ = pointer to key block
 *              @const char *c@ = pointer to comment to set, or zero
 *
 * Returns:     Error code (one of the @KERR@ constants).
 *
 * Use:         Replaces the key's current comment with a new one.
 */

extern int key_setcomment(key_file */*f*/, key */*k*/, const char */*c*/);

/* --- @key_settag@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to key file block
 *              @key *k@ = pointer to key block
 *              @const char *tag@ = pointer to comment to set, or zero
 *
 * Returns:     Error code (one of the @KERR@ constants).
 *
 * Use:         Replaces the key's current tag with a new one.
 */

extern int key_settag(key_file */*f*/, key */*k*/, const char */*tag*/);

/* --- @key_fulltag@ --- *
 *
 * Arguments:   @key *k@ = pointer to key
 *              @dstr *d@ = pointer to destination string
 *
 * Returns:     ---
 *
 * Use:         Emits the key's full tag, which has the form
 *              `ID:TYPE[:TAG]'.  This is used in the textual file format,
 *              and to identify passphrases for locked keys.
 */

extern void key_fulltag(key */*k*/, dstr */*d*/);

/* --- @key_qtag@ --- *
 *
 * Arguments:   @key_file *f@ = key file to find a key from
 *              @const char *tag@ = pointer to tag string
 *              @dstr *d@ = pointer to string for full tag name
 *              @key **k@ = where to store the key pointer
 *              @key_data **kd@ = where to store the key data pointer
 *
 * Returns:     Zero if OK, nonzero if it failed.
 *
 * Use:         Performs a full lookup on a qualified tag name.  The tag is
 *              qualified by the names of subkeys, separated by dots.  Hence,
 *              a qualified tag is ID|TAG[.TAG...].  The various result
 *              pointers can be null to indicate that the result isn't
 *              interesting. 
 */

extern int key_qtag(key_file */*f*/, const char */*tag*/,
                    dstr */*d*/, key **/*k*/, key_data **/*kd*/);

/* --- @key_getattr@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file
 *              @key *k@ = pointer to key
 *              @const char *n@ = pointer to attribute name
 *
 * Returns:     Pointer to attribute value, or null if not found.
 *
 * Use:         Returns the value of a key attribute.
 */

extern const char *key_getattr(key_file */*f*/, key */*k*/,
                               const char */*n*/);

/* --- @key_putattr@ --- *
 *
 * Arguments:   @key_file *f@ = pointer to file
 *              @key *k@ = pointer to key
 *              @const char *n@ = pointer to attribute name
 *              @const char *v@ = pointer to attribute value or null
 *
 * Returns:     Error code (one of the @KERR@ constants).
 *
 * Use:         Inserts an attribute on a key.  If an attribute with the same
 *              name already exists, it is deleted.  Setting a null value
 *              removes the attribute.
 */

extern int key_putattr(key_file */*f*/, key */*k*/,
                       const char */*n*/, const char */*v*/);

/* --- @key_mkattriter@ --- *
 *
 * Arguments:   @key_attriter *i@ = pointer to attribute iterator
 *              @key *k@ = pointer to key
 *
 * Returns:     ---
 *
 * Use:         Initializes an attribute iterator.  The attributes are
 *              returned by @key_nextattr@.
 */

extern void key_mkattriter(key_attriter */*i*/, key */*k*/);

/* --- @key_nextattr@ --- *
 *
 * Arguments:   @key_attriter *i@ = pointer to attribute iterator
 *              @const char **n, **v@ = pointers to name and value
 *
 * Returns:     Zero if no attribute available, or nonzero if returned OK.
 *
 * Use:         Returns the next attribute.
 */

extern int key_nextattr(key_attriter */*i*/,
                        const char **/*n*/, const char **/*v*/);

/*----- Searching and iterating -------------------------------------------*/

/* --- @key_bytype@ --- *
 *
 * Arguments:   @key_file *f@ = key file we want a key from
 *              @const char *type@ = type string for desired key
 *
 * Returns:     Pointer to the best key to use, or null.
 *
 * Use:         Looks up a key by its type.  Returns the key with the latest
 *              expiry time.  This function will not return an expired key.
 */

extern key *key_bytype(key_file */*f*/, const char */*type*/);

/* --- @key_byid@ --- *
 *
 * Arguments:   @key_file *f@ = key file to find a key from
 *              @uint32 id@ = id to look for
 *
 * Returns:     Key with matching id.
 *
 * Use:         Returns a key given its id.  This function will return an
 *              expired key, but not a deleted one.
 */

extern key *key_byid(key_file */*f*/, uint32 /*id*/);

/* --- @key_bytag@ --- *
 *
 * Arguments:   @key_file *f@ = key file to find a key from
 *              @const char *tag@ = pointer to tag string
 *
 * Returns:     Key with matching id or tag.
 *
 * Use:         Returns a key given its tag or id.  This function will return
 *              an expired key, but not a deleted one.
 */

extern key *key_bytag(key_file */*f*/, const char */*tag*/);

/* --- @key_mkiter@ --- *
 *
 * Arguments:   @key_iter *i@ = pointer to iterator object
 *              @key_file *f@ = pointer to file structure
 *
 * Returns:     ---
 *
 * Use:         Initializes a key iterator.  The keys are returned by
 *              @key_next@.
 */

extern void key_mkiter(key_iter */*i*/, key_file */*f*/);

/* --- @key_next@ --- *
 *
 * Arguments:   @key_iter *i@ = pointer to iterator object
 *
 * Returns:     Pointer to next key, or null.
 *
 * Use:         Returns the next key in some arbitrary sequence.
 */

extern key *key_next(key_iter */*i*/);

/*----- Fetching key data conveniently ------------------------------------*/

/* --- @key_fetchinit@ --- *
 *
 * Arguments:   @const key_fetchdef *kf@ = pointer to base definition
 *              @key_packstruct *kps@ = pointer to destination packing def
 *              @void *p@ = pointer to destination block
 *
 * Returns:     Pointer to packing definition.
 *
 * Use:         Initializes a packing definition (@key_packdef@ structure).
 *              If @kps@ is null on entry, an appropriately sized block is
 *              allocated automatically.  Otherwise it must be large enough.
 */

extern key_packdef *key_fetchinit(const key_fetchdef */*kf*/,
                                  key_packstruct */*kp*/, void */*p*/);

/* --- @key_fetch@ --- *
 *
 * Arguments:   @key_packdef *kp@ = pointer to packing structure
 *              @key *k@ = key file containing desired key
 *
 * Returns:     Error code, or zero.
 *
 * Use:         Fetches an unpacked key from a packed one.
 */

extern int key_fetch(key_packdef */*kp*/, key */*k*/);

/* --- @key_fetchbyname@ --- *
 *
 * Arguments:   @key_packdef *kp@ = pointer to packing structure
 *              @key_file *kf@ = key file containing desired key
 *              @const char *tag@ = user's tag describing the key
 *
 * Returns:     Error code, or zero.
 *
 * Use:         Fetches a named key from a key file and unpacks it
 *              conveniently.
 */

extern int key_fetchbyname(key_packdef */*kp*/,
                           key_file */*kf*/, const char */*tag*/);

/* --- @key_fetchdone@ --- *
 *
 * Arguments:   @key_packdef *kp@ = pointer to packing structure
 *
 * Returns:     ---
 *
 * Use:         Frees a packing structure.  If the structure was allocated by
 *              @key_fetchinit@ then it is freed.
 */

extern void key_fetchdone(key_packdef */*kp*/);

/*----- Other functions ---------------------------------------------------*/

/* --- @key_moan@ --- *
 *
 * Arguments:   @const char *file@ = name of the file
 *              @int line@ = line number in file
 *              @const char *msg@ = error message
 *              @void *p@ = argument pointer
 *
 * Returns:     ---
 *
 * Use:         Reports an error message about loading a key file.
 */

extern void key_moan(const char */*file*/, int /*line*/,
                     const char */*msg*/, void */*p*/);

/* --- @key_strerror@ --- *
 *
 * Arguments:   @int err@ = error code from @key_new@
 *
 * Returns:     Pointer to error string.
 *
 * Use:         Translates a @KERR@ error code into a human-readable string.
 */

extern const char *key_strerror(int /*err*/);

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif