| /* |
| * is_tar() -- figure out whether file is a tar archive. |
| * |
| * Stolen (by the author of the file utility!) from the public domain tar program: |
| * Public Domain version written 26 Aug 1985 John Gilmore (ihnp4!hoptoad!gnu). |
| * |
| * @(#)list.c 1.18 9/23/86 Public Domain - gnu |
| * $Id: is_tar.c,v 1.2 2006/06/17 21:00:44 tkojm Exp $ |
| * |
| * Comments changed and some code/comments reformatted |
| * for file command by Ian Darwin. |
| */ |
| |
| #if HAVE_CONFIG_H |
| #include "clamav-config.h" |
| #endif |
| |
| #include <string.h> |
| #include <ctype.h> |
| #include <sys/types.h> |
| #include "is_tar.h" |
| |
| #include "others.h" |
| |
| #define isodigit(c) ( ((c) >= '0') && ((c) <= '7') ) |
| |
| static int from_oct(int digs, char *where); |
| |
| /* |
| * Return |
| * 0 if the checksum is bad (i.e., probably not a tar archive), |
| * 1 for old UNIX tar file, |
| * 2 for Unix Std (POSIX) tar file. |
| */ |
| int is_tar(unsigned char *buf, unsigned int nbytes) |
| { |
| union record *header = (union record *)buf; |
| int i; |
| int sum, recsum; |
| char *p; |
| |
| |
| if (nbytes < sizeof(union record)) |
| return 0; |
| |
| recsum = from_oct(8, header->header.chksum); |
| |
| sum = 0; |
| p = header->charptr; |
| for (i = sizeof(union record); --i >= 0;) { |
| /* |
| * We can't use unsigned char here because of old compilers, |
| * e.g. V7. |
| */ |
| sum += 0xFF & *p++; |
| } |
| |
| /* Adjust checksum to count the "chksum" field as blanks. */ |
| for (i = sizeof(header->header.chksum); --i >= 0;) |
| sum -= 0xFF & header->header.chksum[i]; |
| sum += ' '* sizeof header->header.chksum; |
| |
| if (sum != recsum) |
| return 0; /* Not a tar archive */ |
| |
| if (0==strcmp(header->header.magic, TMAGIC)) |
| return 2; /* Unix Standard tar archive */ |
| |
| return 1; /* Old fashioned tar archive */ |
| } |
| |
| |
| /* |
| * Quick and dirty octal conversion. |
| * |
| * Result is -1 if the field is invalid (all blank, or nonoctal). |
| */ |
| static int from_oct(int digs, char *where) |
| { |
| int value; |
| |
| while (isspace((unsigned char)*where)) { /* Skip spaces */ |
| where++; |
| if (--digs <= 0) |
| return -1; /* All blank field */ |
| } |
| value = 0; |
| while (digs > 0 && isodigit(*where)) { /* Scan til nonoctal */ |
| value = (value << 3) | (*where++ - '0'); |
| --digs; |
| } |
| |
| if (digs > 0 && *where && !isspace((unsigned char)*where)) |
| return -1; /* Ended on non-space/nul */ |
| |
| return value; |
| } |