[u/mdw/catacomb] / dsig.c

/* -*-c-*-
 *
 * $Id: dsig.c,v 1.12 2004/04/17 09:58:37 mdw Exp $
 *
 * Verify signatures on distribuitions of files
 *
 * (c) 2000 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.
 */

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

#include "config.h"

#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <mLib/alloc.h>
#include <mLib/base64.h>
#include <mLib/mdwopt.h>
#include <mLib/quis.h>
#include <mLib/report.h>
#include <mLib/sub.h>

#include "getdate.h"
#include "rand.h"
#include "ghash.h"
#include "key.h"
#include "key-data.h"
#include "noise.h"
#include "cc.h"

/*----- Data formatting ---------------------------------------------------*/

/* --- Binary data structure --- *
 *
 * The binary format, which is used for hashing and for the optional binary
 * output, consists of a sequence of tagged blocks.  The tag describes the
 * format and meaining of the following data.
 */

enum {
  /* --- Block tags --- */

  T_IDENT = 0,                          /* An identifying marker */
  T_KEYID,                              /* Key identifier */
  T_BEGIN,                              /* Begin hashing here */
  T_COMMENT = T_BEGIN,                  /* A textual comment */
  T_DATE,                               /* Creation date of signature */
  T_EXPIRE,                             /* Expiry date of signature */
  T_FILE,                               /* File and corresponding hash */
  T_SIGNATURE,                          /* Final signature block */

  /* --- Error messages --- */

  E_EOF = -1,
  E_BIN = -2,
  E_TAG = -3,
  E_DATE = -4
};

/* --- Name translation table --- */

static const char *tagtab[] = {
  "ident:", "keyid:",
  "comment:", "date:", "expires:", "file:",
  "signature:",
  0
};

static const char *errtab[] = {
  "Off-by-one bug",
  "Unexpected end-of-file",
  "Binary object too large",
  "Unrecognized tag",
  "Bad date string"
};

/* --- Memory representation of block types --- */

typedef struct block {
  int tag;                              /* Type tag */
  dstr d;                               /* String data */
  dstr b;                               /* Binary data */
  time_t t;                             /* Timestamp */
  uint32 k;                             /* Keyid */
} block;

/* --- @getstring@ --- *
 *
 * Arguments:   @FILE *fp@ = stream from which to read
 *              @dstr *d@ = destination string
 *              @unsigned raw@ = raw or cooked read
 *
 * Returns:     Zero if OK, nonzero on end-of-file.
 *
 * Use:         Reads a filename (or something similar) from a stream.
 */

static int getstring(FILE *fp, dstr *d, unsigned raw)
{
  int ch;
  int q = 0;

  /* --- Raw: just read exactly what's written up to a null byte --- */

  if (raw) {
    if ((ch = getc(fp)) == EOF)
      return (EOF);
    for (;;) {
      if (!ch)
        break;
      DPUTC(d, ch);
      if ((ch = getc(fp)) == EOF)
        break;
    }
    DPUTZ(d);
    return (0);
  }

  /* --- Skip as far as whitespace --- *
   *
   * Also skip past comments.
   */

again:
  ch = getc(fp);
  while (isspace(ch))
    ch = getc(fp);
  if (ch == '#') {
    do ch = getc(fp); while (ch != '\n' && ch != EOF);
    goto again;
  }
  if (ch == EOF)
    return (EOF);

  /* --- If the character is a quote then read a quoted string --- */

  switch (ch) {
    case '`':
      ch = '\'';
    case '\'':
    case '\"':
      q = ch;
      ch = getc(fp);
      break;
  }

  /* --- Now read all sorts of interesting things --- */

  for (;;) {

    /* --- Handle an escaped thing --- */

    if (ch == '\\') {
      ch = getc(fp);
      if (ch == EOF)
        break;
      switch (ch) {
        case 'a': ch = '\a'; break;
        case 'b': ch = '\b'; break;
        case 'f': ch = '\f'; break;
        case 'n': ch = '\n'; break;
        case 'r': ch = '\r'; break;
        case 't': ch = '\t'; break;
        case 'v': ch = '\v'; break;
      }
      DPUTC(d, ch);
      ch = getc(fp);
      continue;
    }

    /* --- If it's a quote or some other end marker then stop --- */

    if (ch == q || (!q && isspace((unsigned char)ch)))
      break;

    /* --- Otherwise contribute and continue --- */

    DPUTC(d, ch);
    if ((ch = getc(fp)) == EOF)
      break;
  }

  /* --- Done --- */

  DPUTZ(d);
  return (0);
}

/* --- @putstring@ --- *
 *
 * Arguments:   @FILE *fp@ = stream to write on
 *              @const char *p@ = pointer to text
 *              @unsigned raw@ = whether the string is to be written raw
 *
 * Returns:     ---
 *
 * Use:         Emits a string to a stream.
 */

static void putstring(FILE *fp, const char *p, unsigned raw)
{
  size_t sz = strlen(p);
  unsigned qq;
  const char *q;

  /* --- Just write the string null terminated if raw --- */

  if (raw) {
    fwrite(p, 1, sz + 1, fp);
    return;
  }

  /* --- Check for any dodgy characters --- */

  qq = 0;
  for (q = p; *q; q++) {
    if (isspace((unsigned char)*q)) {
      qq = '\"';
      break;
    }
  }

  if (qq)
    putc(qq, fp);

  /* --- Emit the string --- */

  for (q = p; *q; q++) {
    switch (*q) {
      case '\a': fputc('\\', fp); fputc('a', fp); break;
      case '\b': fputc('\\', fp); fputc('b', fp); break;
      case '\f': fputc('\\', fp); fputc('f', fp); break;
      case '\n': fputc('\\', fp); fputc('n', fp); break;
      case '\r': fputc('\\', fp); fputc('r', fp); break;
      case '\t': fputc('\\', fp); fputc('t', fp); break;
      case '\v': fputc('\\', fp); fputc('v', fp); break;
      case '`': fputc('\\', fp); fputc('`', fp); break;
      case '\'': fputc('\\', fp); fputc('\'', fp); break;
      case '\"': fputc('\\', fp); fputc('\"', fp); break;
      default:
        putc(*q, fp);
        break;
    }
  }

  /* --- Done --- */

  if (qq)
    putc(qq, fp);
}

/* --- @timestring@ --- *
 *
 * Arguments:   @time_t t@ = a timestamp
 *              @dstr *d@ = a string to write on
 *
 * Returns:     ---
 *
 * Use:         Writes a textual representation of the timestamp to the
 *              string.
 */

static void timestring(time_t t, dstr *d)
{
  if (t == KEXP_FOREVER)
    DPUTS(d, "forever");
  else {
    struct tm *tm = localtime(&t);
    DENSURE(d, 32);
    d->len += strftime(d->buf + d->len, 32, "%Y-%m-%d %H:%M:%S %Z", tm);
    DPUTZ(d);
  }
}

/* --- @breset@ --- *
 *
 * Arguments:   @block *b@ = block to reset
 *
 * Returns:     ---
 *
 * Use:         Resets a block so that more stuff can be put in it.
 */

static void breset(block *b)
{
  b->tag = 0;
  DRESET(&b->d);
  DRESET(&b->b);
  b->k = 0;
  b->t = KEXP_EXPIRE;
}

/* --- @binit@ --- *
 *
 * Arguments:   @block *b@ = block to initialize
 *
 * Returns:     ---
 *
 * Use:         Initializes a block as something to read into.
 */

static void binit(block *b)
{
  dstr_create(&b->d);
  dstr_create(&b->b);
  breset(b);
}

/* --- @bdestroy@ --- *
 *
 * Arguments:   @block *b@ = block to destroy
 *
 * Returns:     ---
 *
 * Use:         Destroys a block's contents.
 */

static void bdestroy(block *b)
{
  dstr_destroy(&b->d);
  dstr_destroy(&b->b);
}

/* --- @bget@ --- *
 *
 * Arguments:   @block *b@ = pointer to block
 *              @FILE *fp@ = stream to read from
 *              @unsigned bin@ = binary switch
 *
 * Returns:     Tag of block, or an error tag.
 *
 * Use:         Reads a block from a stream.
 */

static int bget(block *b, FILE *fp, unsigned bin)
{
  int tag;

  /* --- Read the tag --- */

  if (bin)
    tag = getc(fp);
  else {
    dstr d = DSTR_INIT;
    if (getstring(fp, &d, 0))
      return (E_EOF);
    for (tag = 0; tagtab[tag]; tag++) {
      if (strcmp(tagtab[tag], d.buf) == 0)
        goto done;
    }
    return (E_TAG);
  done:;
  }

  /* --- Decide what to do next --- */

  breset(b);
  b->tag = tag;
  switch (tag) {

    /* --- Reading of strings --- */

    case T_IDENT:
    case T_COMMENT:
      if (getstring(fp, &b->d, bin))
        return (E_EOF);
      break;

    /* --- Timestamps --- */

    case T_DATE:
    case T_EXPIRE:
      if (bin) {
        octet buf[8];
        if (fread(buf, sizeof(buf), 1, fp) < 1)
          return (E_EOF);
        b->t = ((time_t)(((LOAD32(buf + 0) << 16) << 16) & ~MASK32) |
                (time_t)LOAD32(buf + 4));
      } else {
        if (getstring(fp, &b->d, 0))
          return (E_EOF);
        if (strcmp(b->d.buf, "forever") == 0)
          b->t = KEXP_FOREVER;
        else if ((b->t = get_date(b->d.buf, 0)) == -1)
          return (E_DATE);
      }
      break;

    /* --- Key ids --- */

    case T_KEYID:
      if (bin) {
        octet buf[4];
        if (fread(buf, sizeof(buf), 1, fp) < 1)
          return (E_EOF);
        b->k = LOAD32(buf);
      } else {
        if (getstring(fp, &b->d, 0))
          return (E_EOF);
        b->k = strtoul(b->d.buf, 0, 16);
      }
      break;

    /* --- Reading of binary data --- */

    case T_FILE:
    case T_SIGNATURE:
      if (bin) {
        octet buf[2];
        uint32 sz;
        if (fread(buf, sizeof(buf), 1, fp) < 1)
          return (E_EOF);
        sz = LOAD16(buf);
        if (sz > 4096)
          return (E_BIN);
        DENSURE(&b->b, sz);
        if (fread(b->b.buf + b->b.len, 1, sz, fp) < sz)
          return (E_EOF);
        b->b.len += sz;
      } else {
        base64_ctx b64;
        if (getstring(fp, &b->d, 0))
          return (E_EOF);
        base64_init(&b64);
        base64_decode(&b64, b->d.buf, b->d.len, &b->b);
        base64_decode(&b64, 0, 0, &b->b);
        DRESET(&b->d);
      }
      if (tag == T_FILE && getstring(fp, &b->d, bin))
        return (E_EOF);
      break;

      /* --- Anything else --- */

    default:
      return (E_TAG);
  }

  return (tag);
}

/* --- @blob@ --- *
 *
 * Arguments:   @block *b@ = pointer to block to emit
 *              @dstr *d@ = output buffer
 *
 * Returns:     ---
 *
 * Use:         Encodes a block in a binary format.
 */

static void blob(block *b, dstr *d)
{
  DPUTC(d, b->tag);
  switch (b->tag) {
    case T_IDENT:
    case T_COMMENT:
      DPUTD(d, &b->d);
      DPUTC(d, 0);
      break;
    case T_DATE:
    case T_EXPIRE:
      DENSURE(d, 8);
      STORE32(d->buf + d->len, ((b->t & ~MASK32) >> 16) >> 16);
      STORE32(d->buf + d->len + 4, b->t);
      d->len += 8;
      break;
    case T_KEYID:
      DENSURE(d, 4);
      STORE32(d->buf + d->len, b->k);
      d->len += 4;
      break;
    case T_FILE:
    case T_SIGNATURE:
      DENSURE(d, 2);
      STORE16(d->buf + d->len, b->b.len);
      d->len += 2;
      DPUTD(d, &b->b);
      if (b->tag == T_FILE) {
        DPUTD(d, &b->d);
        DPUTC(d, 0);
      }
      break;
  }
}

/* --- @bwrite@ --- *
 *
 * Arguments:   @block *b@ = pointer to block to write
 *              @FILE *fp@ = stream to write on
 *
 * Returns:     ---
 *
 * Use:         Writes a block on a stream in a textual format.
 */

static void bwrite(block *b, FILE *fp)
{
  fputs(tagtab[b->tag], fp);
  putc(' ', fp);
  switch (b->tag) {
    case T_IDENT:
    case T_COMMENT:
      putstring(fp, b->d.buf, 0);
      break;
    case T_DATE:
    case T_EXPIRE: {
      dstr d = DSTR_INIT;
      timestring(b->t, &d);
      putstring(fp, d.buf, 0);
      dstr_destroy(&d);
    } break;
    case T_KEYID:
      fprintf(fp, "%08lx", (unsigned long)b->k);
      break;
    case T_FILE:
    case T_SIGNATURE: {
      dstr d = DSTR_INIT;
      base64_ctx b64;
      base64_init(&b64);
      b64.maxline = 0;
      base64_encode(&b64, b->b.buf, b->b.len, &d);
      base64_encode(&b64, 0, 0, &d);
      dstr_write(&d, fp);
      if (b->tag == T_FILE) {
        putc(' ', fp);
        putstring(fp, b->d.buf, 0);
      }
    } break;
  }
  putc('\n', fp);
}

/* --- @bemit@ --- *
 *
 * Arguments:   @block *b@ = pointer to block to write
 *              @FILE *fp@ = file to write on
 *              @ghash *h@ = pointer to hash function
 *              @unsigned bin@ = binary/text flag
 *
 * Returns:     ---
 *
 * Use:         Spits out a block properly.
 */

static void bemit(block *b, FILE *fp, ghash *h, unsigned bin)
{
  if (h || (fp && bin)) {
    dstr d = DSTR_INIT;
    blob(b, &d);
    if (h)
      GH_HASH(h, d.buf, d.len);
    if (fp && bin)
      fwrite(d.buf, d.len, 1, fp);
  }
  if (fp && !bin)
    bwrite(b, fp);
}
    
/*----- Static variables --------------------------------------------------*/

static const char *keyring = "keyring";

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

/* --- @keyreport@ --- *
 *
 * Arguments:   @const char *file@ = filename containing the error
 *              @int line@ = line number in file
 *              @const char *err@ = error text message
 *              @void *p@ = unimportant pointer
 *
 * Returns:     ---
 *
 * Use:         Reports errors during the opening of a key file.
 */

static void keyreport(const char *file, int line, const char *err, void *p)
{
  moan("error in keyring `%s' at line `%s': %s", file, line, err);
}

/* --- @fhash@ --- *
 *
 * Arguments:   @const gchash *c@ = pointer to hash class
 *              @const char *file@ = file to hash
 *              @void *b@ = pointer to output buffer
 *
 * Returns:     Zero if it worked, or nonzero for a system error.
 *
 * Use:         Hashes a file.
 */

static int fhash(const gchash *c, const char *file, void *b)
{
  FILE *fp = fopen(file, "rb");
  ghash *h = GH_INIT(c);
  char buf[4096];
  size_t sz;
  int rc = 0;

  if (!fp)
    return (-1);
  while ((sz = fread(buf, 1, sizeof(buf), fp)) > 0)
    GH_HASH(h, buf, sz);
  if (ferror(fp))
    rc = -1;
  GH_DONE(h, b);
  GH_DESTROY(h);
  fclose(fp);
  return (rc);
}

/* --- @fhex@ --- *
 *
 * Arguments:   @FILE *fp@ = file to write on
 *              @const void *p@ = pointer to data to be written
 *              @size_t sz@ = size of the data to write
 *
 * Returns:     ---
 *
 * Use:         Emits a hex dump to a stream.
 */

static void fhex(FILE *fp, const void *p, size_t sz)
{
  const octet *q = p;
  if (!sz)
    return;
  for (;;) {
    fprintf(fp, "%02x", *q++);
    sz--;
    if (!sz)
      break;
  }
}    

/*----- Signature generation ----------------------------------------------*/

static int sign(int argc, char *argv[])
{
#define f_raw 1u
#define f_bin 2u
#define f_bogus 4u

  unsigned f = 0;
  const char *ki = "dsig";
  key_file kf;
  key *k;
  sig *s;
  time_t exp = KEXP_EXPIRE;
  unsigned verb = 0;
  const char *ifile = 0;
  const char *ofile = 0;
  const char *c = 0;
  const char *err;
  FILE *ifp, *ofp;
  dstr d = DSTR_INIT;
  block b;
  int e;

  for (;;) {
    static struct option opts[] = {
      { "null",         0,              0,      '0' },
      { "binary",       0,              0,      'b' },
      { "verbose",      0,              0,      'v' },
      { "quiet",        0,              0,      'q' },
      { "comment",      OPTF_ARGREQ,    0,      'c' },
      { "file",         OPTF_ARGREQ,    0,      'f' },
      { "output",       OPTF_ARGREQ,    0,      'o' },
      { "key",          OPTF_ARGREQ,    0,      'k' },
      { "expire",       OPTF_ARGREQ,    0,      'e' },
      { 0,              0,              0,      0 }
    };
    int i = mdwopt(argc, argv, "+0vqb" "c:" "f:o:" "k:e:", opts, 0, 0, 0);
    if (i < 0)
      break;
    switch (i) {
      case '0':
        f |= f_raw;
        break;
      case 'b':
        f |= f_bin;
        break;
      case 'v':
        verb++;
        break;
      case 'q':
        if (verb > 0)
          verb--;
        break;
      case 'c':
        c = optarg;
        break;
      case 'f':
        ifile = optarg;
        break;
      case 'o':
        ofile = optarg;
        break;
      case 'k':
        ki = optarg;
        break;
      case 'e':
        if (strcmp(optarg, "forever") == 0)
          exp = KEXP_FOREVER;
        else if ((exp = get_date(optarg, 0)) == -1)
          die(EXIT_FAILURE, "bad expiry time");
        break;
      default:
        f |= f_bogus;
        break;
    }
  }
  if (optind != argc || (f & f_bogus))
    die(EXIT_FAILURE, "Usage: sign [-options]");

  /* --- Locate the signing key --- */

  if (key_open(&kf, keyring, KOPEN_WRITE, keyreport, 0))
    die(EXIT_FAILURE, "couldn't open keyring `%s'", keyring);
  if ((k = key_bytag(&kf, ki)) == 0)
    die(EXIT_FAILURE, "couldn't find key `%s'", ki);
  key_fulltag(k, &d);
  if (exp == KEXP_FOREVER && k->exp != KEXP_FOREVER) {
    die(EXIT_FAILURE, "key `%s' expires: can't create nonexpiring signature",
        d.buf);
  }
  s = getsig(k, "dsig", 1);

  /* --- Check the key --- */

  if ((err = s->ops->check(s)) != 0)
    moan("key `%s' fails check: %s", d.buf, err);

  /* --- Open files --- */

  if (!ifile)
    ifp = stdin;
  else if ((ifp = fopen(ifile, (f & f_raw) ? "rb" : "r")) == 0) {
    die(EXIT_FAILURE, "couldn't open input file `%s': %s",
        ifile, strerror(errno));
  }

  if (!ofile)
    ofp = stdout;
  else if ((ofp = fopen(ofile, (f & f_bin) ? "wb" : "w")) == 0) {
    die(EXIT_FAILURE, "couldn't open output file `%s': %s",
        ofile, strerror(errno));
  }

  /* --- Emit the start of the output --- */

  binit(&b); b.tag = T_IDENT;
  dstr_putf(&b.d, "%s, Catacomb version " VERSION, QUIS);
  bemit(&b, ofp, 0, f & f_bin);
  
  breset(&b); b.tag = T_KEYID; b.k = k->id;
  bemit(&b, ofp, 0, f & f_bin);

  /* --- Start hashing, and emit the datestamps and things --- */

  {
    time_t now = time(0);

    breset(&b); b.tag = T_DATE; b.t = now; bemit(&b, ofp, s->h, f & f_bin);
    if (exp == KEXP_EXPIRE)
      exp = now + 86400 * 28;
    breset(&b); b.tag = T_EXPIRE; b.t = exp; bemit(&b, ofp, s->h, f & f_bin);
    if (c) {
      breset(&b); b.tag = T_COMMENT; DPUTS(&b.d, c);
      bemit(&b, ofp, s->h, f & f_bin);
    }

    if (!(f & f_bin))
      putc('\n', ofp);
  }

  /* --- Now hash the various files --- */

  for (;;) {

    /* --- Stop on an output error --- */

    if (ferror(ofp)) {
      f |= f_bogus;
      break;
    }

    /* --- Read the next filename to hash --- */

    breset(&b);
    if (getstring(ifp, &b.d, f & f_raw))
      break;
    b.tag = T_FILE;
    DENSURE(&b.b, GH_CLASS(s->h)->hashsz);
    if (fhash(GH_CLASS(s->h), b.d.buf, b.b.buf)) {
      moan("Error reading `%s': %s", b.d.buf, strerror(errno));
      f |= f_bogus;
    } else {
      b.b.len += GH_CLASS(s->h)->hashsz;
      if (verb) {
        fhex(stderr, b.b.buf, b.b.len);
        fprintf(stderr, " %s\n", b.d.buf);
      }
      bemit(&b, ofp, s->h, f & f_bin);
    }
  }

  /* --- Create the signature --- */

  if (!(f & f_bogus)) {
    breset(&b);
    b.tag = T_SIGNATURE;
    if ((e = s->ops->doit(s, &b.b)) != 0) {
      moan("error creating signature: %s", key_strerror(e));
      f |= f_bogus;
    }
    if (!(f & f_bogus)) {
      bemit(&b, ofp, 0, f & f_bin);
      key_used(&kf, k, exp);
    }
  }

  /* --- Tidy up at the end --- */

  freesig(s);
  bdestroy(&b);
  if (ifile)
    fclose(ifp);
  if (ofile) {
    if (fclose(ofp))
      f |= f_bogus;
  } else {
    if (fflush(ofp))
      f |= f_bogus;
  }
  if ((e = key_close(&kf)) != 0) {
    switch (e) {
      case KWRITE_FAIL:
        die(EXIT_FAILURE, "couldn't write file `%s': %s",
            keyring, strerror(errno));
      case KWRITE_BROKEN:
        die(EXIT_FAILURE, "keyring file `%s' broken: %s (repair manually)",
            keyring, strerror(errno));
    }
  }
  if (f & f_bogus)
    die(EXIT_FAILURE, "error(s) occurred while creating signature");
  return (EXIT_SUCCESS);

#undef f_raw
#undef f_bin
#undef f_bogus
}

/*----- Signature verification --------------------------------------------*/

static int verify(int argc, char *argv[])
{
#define f_bogus 1u
#define f_bin 2u
#define f_ok 4u

  unsigned f = 0;
  unsigned verb = 1;
  key_file kf;
  key *k = 0;
  sig *s;
  dstr d = DSTR_INIT;
  const char *err;
  FILE *fp;
  block b;
  int e;

  /* --- Parse the options --- */

  for (;;) {
    static struct option opts[] = {
      { "verbose",      0,              0,      'v' },
      { "quiet",        0,              0,      'q' },
      { 0,              0,              0,      0 }
    };
    int i = mdwopt(argc, argv, "+vq", opts, 0, 0, 0);
    if (i < 0)
      break;
    switch (i) {
      case 'v':
        verb++;
        break;
      case 'q':
        if (verb)
          verb--;
        break;
      default:
        f |= f_bogus;
        break;
    }
  }
  argc -= optind;
  argv += optind;
  if ((f & f_bogus) || argc > 1)
    die(EXIT_FAILURE, "Usage: verify [-qv] [file]");

  /* --- Open the key file, and start reading the input file --- */

  if (key_open(&kf, keyring, KOPEN_READ, keyreport, 0))
    die(EXIT_FAILURE, "couldn't open keyring `%s'\n", keyring);
  if (argc < 1)
    fp = stdin;
  else {
    if ((fp = fopen(argv[0], "rb")) == 0) {
      die(EXIT_FAILURE, "couldn't open file `%s': %s\n",
              argv[0], strerror(errno));
    }
    if (getc(fp) == 0) {
      ungetc(0, fp);
      f |= f_bin;
    } else {
      fclose(fp);
      if ((fp = fopen(argv[0], "r")) == 0) {
        die(EXIT_FAILURE, "couldn't open file `%s': %s\n",
                argv[0], strerror(errno));
      }
    }
  }

  /* --- Read the introductory matter --- */

  binit(&b);
  for (;;) {
    breset(&b);
    e = bget(&b, fp, f & f_bin);
    if (e < 0)
      die(EXIT_FAILURE, "error reading packet: %s", errtab[-e]);
    if (e >= T_BEGIN)
      break;
    switch (e) {
      case T_IDENT:
        if (verb > 2)
          printf("INFO ident: `%s'\n", b.d.buf);
        break;
      case T_KEYID:
        if ((k = key_byid(&kf, b.k)) == 0) {
          if (verb)
            printf("FAIL key %08lx not found\n", (unsigned long)b.k);
          exit(EXIT_FAILURE);
        }
        if (verb > 2) {
          DRESET(&b.d);
          key_fulltag(k, &b.d);
          printf("INFO key: %s\n", b.d.buf);
        }
        break;
      default:
        die(EXIT_FAILURE, "(internal) unknown packet type\n");
        break;
    }
  }

  /* --- Initialize the hash function and start reading hashed packets --- */

  if (!k) {
    if (verb)
      puts("FAIL no keyid packet found");
    exit(EXIT_FAILURE);
  }

  s = getsig(k, "dsig", 0);
  if (verb && (err = s->ops->check(s)) != 0)
    printf("WARN public key fails check: %s", err);

  for (;;) {
    switch (e) {
      case T_COMMENT:
        if (verb > 1)
          printf("INFO comment: `%s'\n", b.d.buf);
        bemit(&b, 0, s->h, 0);
        break;
      case T_DATE:
        if (verb > 2) {
          DRESET(&b.d);
          timestring(b.t, &b.d);
          printf("INFO date: %s\n", b.d.buf);
        }
        bemit(&b, 0, s->h, 0);
        break;
      case T_EXPIRE: {
        time_t now = time(0);
        if (b.t < now) {
          if (verb > 1)
            puts("BAD signature has expired");
          f |= f_bogus;
        }
        if (verb > 2) {
          DRESET(&b.d);
          timestring(b.t, &b.d);
          printf("INFO expires: %s\n", b.d.buf);
        }
        bemit(&b, 0, s->h, 0);
      } break;
      case T_FILE:
        DRESET(&d);
        DENSURE(&d, GH_CLASS(s->h)->hashsz);
        if (fhash(GH_CLASS(s->h), b.d.buf, d.buf)) {
          if (verb > 1) {
            printf("BAD error reading file `%s': %s\n",
                    b.d.buf, strerror(errno));
          }
          f |= f_bogus;
        } else if (b.b.len != GH_CLASS(s->h)->hashsz ||
                   memcmp(d.buf, b.b.buf, b.b.len) != 0) {
          if (verb > 1)
            printf("BAD file `%s' has incorrect hash\n", b.d.buf);
          f |= f_bogus;
        } else if (verb > 3) {
          fputs("INFO hash: ", stdout);
          fhex(stdout, b.b.buf, b.b.len);
          printf(" %s\n", b.d.buf);
        }
        bemit(&b, 0, s->h, 0);
        break;
      case T_SIGNATURE:
        if (s->ops->doit(s, &b.b)) {
          if (verb > 1)
            puts("BAD bad signature");
          f |= f_bogus;
        } else if (verb > 2)
          puts("INFO good signature");
        goto done;
      default:
        if (verb)
          printf("FAIL invalid packet type %i\n", e);
        exit(EXIT_FAILURE);
        break;
    }
    breset(&b);
    e = bget(&b, fp, f & f_bin);
    if (e < 0) {
      if (verb)
        printf("FAIL error reading packet: %s\n", errtab[-e]);
      exit(EXIT_FAILURE);
    }
  }
done:
  bdestroy(&b);
  dstr_destroy(&d);
  freesig(s);
  key_close(&kf);
  if (fp != stdin)
    fclose(fp);
  if (verb) {
    if (f & f_bogus)
      puts("FAIL signature invalid");
    else
      puts("OK signature verified");
  }
  return (f & f_bogus ? EXIT_FAILURE : EXIT_SUCCESS);

#undef f_bogus
#undef f_bin
#undef f_ok
}

/*----- Main code ---------------------------------------------------------*/

typedef struct cmd {
  const char *name;
  int (*func)(int /*argc*/, char */*argv*/[]);
  const char *usage;
  const char *help;
} cmd;

static cmd cmdtab[] = {
  { "sign", sign,
    "sign [-0bqv] [-c comment] [-k tag] [-e expire] [-f file] [-o output]",
    "\
Options:\n\
\n\
-0, --null              Read null-terminated filenames from stdin.\n\
-b, --binary            Produce a binary output file.\n\
-q, --quiet             Produce fewer messages while working.\n\
-v, --verbose           Produce more messages while working.\n\
-c, --comment=COMMENT   Include COMMENT in the output file.\n\
-f, --file=FILE         Read filenames to hash from FILE.\n\
-o, --output=FILE       Write the signed result to FILE.\n\
-k, --key=TAG           Use a key named by TAG.\n\
-e, --expire=TIME       The signature should expire after TIME.\n\
" },
  { "verify", verify,
    "verify [-qv] [file]", "\
Options:\n\
\n\
-q, --quiet             Produce fewer messages while working.\n\
-v, --verbose           Produce more messages while working.\n\
" },
  { 0, 0, 0 }
};

/* --- @findcmd@ --- *
 *
 * Arguments:   @const char *name@ = a command name
 *
 * Returns:     Pointer to the command structure.
 *
 * Use:         Looks up a command by name.  If the command isn't found, an
 *              error is reported and the program is terminated.
 */

static cmd *findcmd(const char *name)
{
  cmd *c, *chosen = 0;
  size_t sz = strlen(name);

  for (c = cmdtab; c->name; c++) {
    if (strncmp(name, c->name, sz) == 0) {
      if (c->name[sz] == 0) {
        chosen = c;
        break;
      } else if (chosen)
        die(EXIT_FAILURE, "ambiguous command name `%s'", name);
      else
        chosen = c;
    }
  }
  if (!chosen)
    die(EXIT_FAILURE, "unknown command name `%s'", name);
  return (chosen);
}

static void version(FILE *fp)
{
  pquis(fp, "$, Catacomb version " VERSION "\n");
}

static void usage(FILE *fp)
{
  pquis(fp, "Usage: $ [-k keyring] command [args]\n");
}

static void help(FILE *fp, char **argv)
{
  cmd *c;

  if (*argv) {
    c = findcmd(*argv);
    fprintf(fp, "Usage: %s [-k keyring] %s\n", QUIS, c->usage);
    if (c->help) {
      fputc('\n', fp);  
      fputs(c->help, fp);
    }
  } else {
    version(fp);
    fputc('\n', fp);
    usage(fp);
    fputs("\n\
Create and verify signatures on lists of files.\n\
\n", fp);
    for (c = cmdtab; c->name; c++)
      fprintf(fp, "%s\n", c->usage);
  }
}

/* --- @main@ --- *
 *
 * Arguments:   @int argc@ = number of command line arguments
 *              @char *argv[]@ = vector of command line arguments
 *
 * Returns:     Zero if successful, nonzero otherwise.
 *
 * Use:         Signs or verifies signatures on lists of files.  Useful for
 *              ensuring that a distribution is unmolested.
 */

int main(int argc, char *argv[])
{
  unsigned f = 0;

#define f_bogus 1u

  /* --- Initialize the library --- */

  ego(argv[0]);
  sub_init();
  rand_noisesrc(RAND_GLOBAL, &noise_source);
  rand_seed(RAND_GLOBAL, 160);

  /* --- Parse options --- */

  for (;;) {
    static struct option opts[] = {
      { "help",         0,              0,      'h' },
      { "version",      0,              0,      'v' },
      { "usage",        0,              0,      'u' },
      { "keyring",      OPTF_ARGREQ,    0,      'k' },
      { 0,              0,              0,      0 }
    };
    int i = mdwopt(argc, argv, "+hvu k:", opts, 0, 0, 0);
    if (i < 0)
      break;
    switch (i) {
      case 'h':
        help(stdout, argv + optind);
        exit(0);
        break;
      case 'v':
        version(stdout);
        exit(0);
        break;
      case 'u':
        usage(stdout);
        exit(0);
      case 'k':
        keyring = optarg;
        break;
      default:
        f |= f_bogus;
        break;
    }
  }

  argc -= optind;
  argv += optind;
  optind = 0;
  if (f & f_bogus || argc < 1) {
    usage(stderr);
    exit(EXIT_FAILURE);
  }

  /* --- Dispatch to the correct subcommand handler --- */

  return (findcmd(argv[0])->func(argc, argv));

#undef f_bogus
}

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