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apprentice.c

/*
 * apprentice - make one pass through /etc/magic, learning its secrets.
 *
 * Copyright (c) Ian F. Darwin, 1987.
 * Written by Ian F. Darwin.
 *
 * This software is not subject to any license of the American Telephone
 * and Telegraph Company or of the Regents of the University of California.
 *
 * Permission is granted to anyone to use this software for any purpose on
 * any computer system, and to alter it and redistribute it freely, subject
 * to the following restrictions:
 *
 * 1. The author is not responsible for the consequences of use of this
 *    software, no matter how awful, even if they arise from flaws in it.
 *
 * 2. The origin of this software must not be misrepresented, either by
 *    explicit claim or by omission.  Since few users ever read sources,
 *    credits must appear in the documentation.
 *
 * 3. Altered versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.  Since few users
 *    ever read sources, credits must appear in the documentation.
 *
 * 4. This notice may not be removed or altered.
 */

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

#ifndef     lint
static char *moduleid =
      "@(#)$Id: apprentice.c,v 1.3 1996/01/23 12:40:04 mpp Exp $";
#endif      /* lint */

#define     EATAB {while (isascii((unsigned char) *l) && \
                  isspace((unsigned char) *l))  ++l;}
#define LOWCASE(l) (isupper((unsigned char) (l)) ? \
                  tolower((unsigned char) (l)) : (l))


static int getvalue     __P((struct magic *, char **));
static int hextoint     __P((int));
static char *getstr     __P((char *, char *, int, int *));
static int parse  __P((char *, int *, int));
static void eatsize     __P((char **));

static int maxmagic = 0;

static int apprentice_1 __P((char *, int));

int
apprentice(fn, check)
char *fn;               /* list of magic files */
int check;              /* non-zero? checking-only run. */
{
      char *p, *mfn;
      int file_err, errs = -1;

        maxmagic = MAXMAGIS;
      magic = (struct magic *) calloc(sizeof(struct magic), maxmagic);
      mfn = malloc(strlen(fn)+1);
      if (magic == NULL || mfn == NULL) {
            (void) fprintf(stderr, "%s: Out of memory.\n", progname);
            if (check)
                  return -1;
            else
                  exit(1);
      }
      fn = strcpy(mfn, fn);
  
      while (fn) {
            p = strchr(fn, ':');
            if (p)
                  *p++ = '\0';
            file_err = apprentice_1(fn, check);
            if (file_err > errs)
                  errs = file_err;
            fn = p;
      }
      if (errs == -1)
            (void) fprintf(stderr, "%s: couldn't find any magic files!\n",
                         progname);
      if (!check && errs)
            exit(1);

      free(mfn);
      return errs;
}

static int
apprentice_1(fn, check)
char *fn;               /* name of magic file */
int check;              /* non-zero? checking-only run. */
{
      static const char hdr[] =
            "cont\toffset\ttype\topcode\tmask\tvalue\tdesc";
      FILE *f;
      char line[BUFSIZ+1];
      int errs = 0;

      f = fopen(fn, "r");
      if (f==NULL) {
            if (errno != ENOENT)
                  (void) fprintf(stderr,
                  "%s: can't read magic file %s (%s)\n", 
                  progname, fn, strerror(errno));
            return -1;
      }

      /* parse it */
      if (check)  /* print silly verbose header for USG compat. */
            (void) printf("%s\n", hdr);

      for (lineno = 1;fgets(line, BUFSIZ, f) != NULL; lineno++) {
            if (line[0]=='#') /* comment, do not parse */
                  continue;
            if (strlen(line) <= (unsigned)1) /* null line, garbage, etc */
                  continue;
            line[strlen(line)-1] = '\0'; /* delete newline */
            if (parse(line, &nmagic, check) != 0)
                  errs = 1;
      }

      (void) fclose(f);
      return errs;
}

/*
 * extend the sign bit if the comparison is to be signed
 */
unsigned long
signextend(m, v)
struct magic *m;
unsigned long v;
{
      if (!(m->flag & UNSIGNED))
            switch(m->type) {
            /*
             * Do not remove the casts below.  They are
             * vital.  When later compared with the data,
             * the sign extension must have happened.
             */
            case BYTE:
                  v = (char) v;
                  break;
            case SHORT:
            case BESHORT:
            case LESHORT:
                  v = (short) v;
                  break;
            case DATE:
            case BEDATE:
            case LEDATE:
            case LONG:
            case BELONG:
            case LELONG:
                  v = (long) v;
                  break;
            case STRING:
                  break;
            default:
                  magwarn("can't happen: m->type=%d\n",
                        m->type);
                  return -1;
            }
      return v;
}

/*
 * parse one line from magic file, put into magic[index++] if valid
 */
static int
parse(l, ndx, check)
char *l;
int *ndx, check;
{
      int i = 0, nd = *ndx;
      struct magic *m;
      char *t, *s;

#define ALLOC_INCR      20
      if (nd+1 >= maxmagic){
          maxmagic += ALLOC_INCR;
          if ((magic = (struct magic *) realloc(magic, 
                                      sizeof(struct magic) * 
                                      maxmagic)) == NULL) {
            (void) fprintf(stderr, "%s: Out of memory.\n", progname);
            if (check)
                  return -1;
            else
                  exit(1);
          }
          memset(&magic[*ndx], 0, sizeof(struct magic) * ALLOC_INCR);
      }
      m = &magic[*ndx];
      m->flag = 0;
      m->cont_level = 0;

      while (*l == '>') {
            ++l;        /* step over */
            m->cont_level++;
      }

      if (m->cont_level != 0 && *l == '(') {
            ++l;        /* step over */
            m->flag |= INDIR;
      }

      /* get offset, then skip over it */
      m->offset = (int) strtoul(l,&t,0);
        if (l == t)
            magwarn("offset %s invalid", l);
        l = t;

      if (m->flag & INDIR) {
            m->in.type = LONG;
            m->in.offset = 0;
            /*
             * read [.lbs][+-]nnnnn)
             */
            if (*l == '.') {
                  l++;
                  switch (LOWCASE(*l)) {
                  case 'l':
                        m->in.type = LONG;
                        break;
                  case 'h':
                  case 's':
                        m->in.type = SHORT;
                        break;
                  case 'c':
                  case 'b':
                        m->in.type = BYTE;
                        break;
                  default:
                        magwarn("indirect offset type %c invalid", *l);
                        break;
                  }
                  l++;
            }
            s = l;
            if (*l == '+' || *l == '-') l++;
            if (isdigit((unsigned char)*l)) {
                  m->in.offset = strtoul(l, &t, 0);
                  if (*s == '-') m->in.offset = - m->in.offset;
            }
            else
                  t = l;
            if (*t++ != ')')
                  magwarn("missing ')' in indirect offset");
            l = t;
      }


      while (isascii((unsigned char)*l) && isdigit((unsigned char)*l))
            ++l;
      EATAB;

#define NBYTE           4
#define NSHORT          5
#define NLONG           4
#define NSTRING   6
#define NDATE           4
#define NBESHORT  7
#define NBELONG         6
#define NBEDATE         6
#define NLESHORT  7
#define NLELONG         6
#define NLEDATE         6

      if (*l == 'u') {
            ++l;
            m->flag |= UNSIGNED;
      }

      /* get type, skip it */
      if (strncmp(l, "byte", NBYTE)==0) {
            m->type = BYTE;
            l += NBYTE;
      } else if (strncmp(l, "short", NSHORT)==0) {
            m->type = SHORT;
            l += NSHORT;
      } else if (strncmp(l, "long", NLONG)==0) {
            m->type = LONG;
            l += NLONG;
      } else if (strncmp(l, "string", NSTRING)==0) {
            m->type = STRING;
            l += NSTRING;
      } else if (strncmp(l, "date", NDATE)==0) {
            m->type = DATE;
            l += NDATE;
      } else if (strncmp(l, "beshort", NBESHORT)==0) {
            m->type = BESHORT;
            l += NBESHORT;
      } else if (strncmp(l, "belong", NBELONG)==0) {
            m->type = BELONG;
            l += NBELONG;
      } else if (strncmp(l, "bedate", NBEDATE)==0) {
            m->type = BEDATE;
            l += NBEDATE;
      } else if (strncmp(l, "leshort", NLESHORT)==0) {
            m->type = LESHORT;
            l += NLESHORT;
      } else if (strncmp(l, "lelong", NLELONG)==0) {
            m->type = LELONG;
            l += NLELONG;
      } else if (strncmp(l, "ledate", NLEDATE)==0) {
            m->type = LEDATE;
            l += NLEDATE;
      } else {
            magwarn("type %s invalid", l);
            return -1;
      }
      /* New-style anding: "0 byte&0x80 =0x80 dynamically linked" */
      if (*l == '&') {
            ++l;
            m->mask = signextend(m, strtoul(l, &l, 0));
            eatsize(&l);
      } else
            m->mask = ~0L;
      EATAB;

      switch (*l) {
      case '>':
      case '<':
      /* Old-style anding: "0 byte &0x80 dynamically linked" */
      case '&':
      case '^':
      case '=':
            m->reln = *l;
            ++l;
            break;
      case '!':
            if (m->type != STRING) {
                  m->reln = *l;
                  ++l;
                  break;
            }
            /* FALL THROUGH */
      default:
            if (*l == 'x' && isascii((unsigned char)l[1]) &&
                isspace((unsigned char)l[1])) {
                  m->reln = *l;
                  ++l;
                  goto GetDesc;     /* Bill The Cat */
            }
            m->reln = '=';
            break;
      }
      EATAB;

      if (getvalue(m, &l))
            return -1;
      /*
       * TODO finish this macro and start using it!
       * #define offsetcheck {if (offset > HOWMANY-1)
       *    magwarn("offset too big"); }
       */

      /*
       * now get last part - the description
       */
GetDesc:
      EATAB;
      if (l[0] == '\b') {
            ++l;
            m->nospflag = 1;
      } else if ((l[0] == '\\') && (l[1] == 'b')) {
            ++l;
            ++l;
            m->nospflag = 1;
      } else
            m->nospflag = 0;
      while ((m->desc[i++] = *l++) != '\0' && i<MAXDESC)
            /* NULLBODY */;

      if (check) {
            mdump(m);
      }
      ++(*ndx);         /* make room for next */
      return 0;
}

/*
 * Read a numeric value from a pointer, into the value union of a magic
 * pointer, according to the magic type.  Update the string pointer to point
 * just after the number read.  Return 0 for success, non-zero for failure.
 */
static int
getvalue(m, p)
struct magic *m;
char **p;
{
      int slen;

      if (m->type == STRING) {
            *p = getstr(*p, m->value.s, sizeof(m->value.s), &slen);
            m->vallen = slen;
      } else
            if (m->reln != 'x') {
                  m->value.l = signextend(m, strtoul(*p, p, 0));
                  eatsize(p);
            }
      return 0;
}

/*
 * Convert a string containing C character escapes.  Stop at an unescaped
 * space or tab.
 * Copy the converted version to "p", returning its length in *slen.
 * Return updated scan pointer as function result.
 */
static char *
getstr(s, p, plen, slen)
register char     *s;
register char     *p;
int   plen, *slen;
{
      char  *origs = s, *origp = p;
      char  *pmax = p + plen - 1;
      register int      c;
      register int      val;

      while ((c = *s++) != '\0') {
            if (isspace((unsigned char) c))
                  break;
            if (p >= pmax) {
                  fprintf(stderr, "String too long: %s\n", origs);
                  break;
            }
            if(c == '\\') {
                  switch(c = *s++) {

                  case '\0':
                        goto out;

                  default:
                        *p++ = (char) c;
                        break;

                  case 'n':
                        *p++ = '\n';
                        break;

                  case 'r':
                        *p++ = '\r';
                        break;

                  case 'b':
                        *p++ = '\b';
                        break;

                  case 't':
                        *p++ = '\t';
                        break;

                  case 'f':
                        *p++ = '\f';
                        break;

                  case 'v':
                        *p++ = '\v';
                        break;

                  /* \ and up to 3 octal digits */
                  case '0':
                  case '1':
                  case '2':
                  case '3':
                  case '4':
                  case '5':
                  case '6':
                  case '7':
                        val = c - '0';
                        c = *s++;  /* try for 2 */
                        if(c >= '0' && c <= '7') {
                              val = (val<<3) | (c - '0');
                              c = *s++;  /* try for 3 */
                              if(c >= '0' && c <= '7')
                                    val = (val<<3) | (c-'0');
                              else
                                    --s;
                        }
                        else
                              --s;
                        *p++ = (char)val;
                        break;

                  /* \x and up to 3 hex digits */
                  case 'x':
                        val = 'x';  /* Default if no digits */
                        c = hextoint(*s++);     /* Get next char */
                        if (c >= 0) {
                              val = c;
                              c = hextoint(*s++);
                              if (c >= 0) {
                                    val = (val << 4) + c;
                                    c = hextoint(*s++);
                                    if (c >= 0) {
                                          val = (val << 4) + c;
                                    } else
                                          --s;
                              } else
                                    --s;
                        } else
                              --s;
                        *p++ = (char)val;
                        break;
                  }
            } else
                  *p++ = (char)c;
      }
out:
      *p = '\0';
      *slen = p - origp;
      return s;
}


/* Single hex char to int; -1 if not a hex char. */
static int
hextoint(c)
int c;
{
      if (!isascii((unsigned char) c))    return -1;
      if (isdigit((unsigned char) c))           return c - '0';
      if ((c>='a')&&(c<='f')) return c + 10 - 'a';
      if ((c>='A')&&(c<='F')) return c + 10 - 'A';
                        return -1;
}


/*
 * Print a string containing C character escapes.
 */
void
showstr(fp, s, len)
FILE *fp;
const char *s;
int len;
{
      register char     c;

      for (;;) {
            c = *s++;
            if (len == -1) {
                  if (c == '\0')
                        break;
            }
            else  {
                  if (len-- == 0)
                        break;
            }
            if(c >= 040 && c <= 0176)     /* TODO isprint && !iscntrl */
                  (void) fputc(c, fp);
            else {
                  (void) fputc('\\', fp);
                  switch (c) {

                  case '\n':
                        (void) fputc('n', fp);
                        break;

                  case '\r':
                        (void) fputc('r', fp);
                        break;

                  case '\b':
                        (void) fputc('b', fp);
                        break;

                  case '\t':
                        (void) fputc('t', fp);
                        break;

                  case '\f':
                        (void) fputc('f', fp);
                        break;

                  case '\v':
                        (void) fputc('v', fp);
                        break;

                  default:
                        (void) fprintf(fp, "%.3o", c & 0377);
                        break;
                  }
            }
      }
}

/*
 * eatsize(): Eat the size spec from a number [eg. 10UL]
 */
static void
eatsize(p)
char **p;
{
      char *l = *p;

      if (LOWCASE(*l) == 'u') 
            l++;

      switch (LOWCASE(*l)) {
      case 'l':    /* long */
      case 's':    /* short */
      case 'h':    /* short */
      case 'b':    /* char/byte */
      case 'c':    /* char/byte */
            l++;
            /*FALLTHROUGH*/
      default:
            break;
      }

      *p = l;
}

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