Add support for signed indirect offsets.

5 files changed, 88 insertions, 276 deletions

diff --git a/ChangeLog b/ChangeLog
index 1f30a1f9..61655de5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2016-07-20   7:26  Christos Zoulas <christos@zoulas.com>
+
+	* Add support for signed indirect offsets
+
+2016-07-18   7:41  Christos Zoulas <christos@zoulas.com>
+
+	* cat /dev/null | file - should print empty (Christoph Biedl)
+
 2016-07-05  15:20  Christos Zoulas <christos@zoulas.com>
 
 	* Bump string size from 64 to 96.
diff --git a/doc/magic.man b/doc/magic.man
index f3b63b46..831e1e4d 100644
--- a/doc/magic.man
+++ b/doc/magic.man
@@ -1,5 +1,5 @@
-.\" $File: magic.man,v 1.86 2015/09/08 13:48:44 christos Exp $
-.Dd January 1, 2015
+.\" $File: magic.man,v 1.87 2016/07/20 11:27:08 christos Exp $
+.Dd July 20, 2016
 .Dt MAGIC __FSECTION__
 .Os
 .\" install as magic.4 on USG, magic.5 on V7, Berkeley and Linux systems.
@@ -535,13 +535,18 @@ the file.
 The value at that offset is read, and is used again as an offset
 in the file.
 Indirect offsets are of the form:
-.Em (( x [.[bislBISL]][+\-][ y ]) .
+.Em (( x [[.,][bislBISL]][+\-][ y ]) .
 The value of
 .Em x
 is used as an offset in the file.
 A byte, id3 length, short or long is read at that offset depending on the
 .Em [bislBISLm]
 type specifier.
+The value is treated as signed if
+.Dq ,
+is specified or unsigned if
+.Dq .
+is specified.
 The capitalized types interpret the number as a big endian
 value, whereas the small letter versions interpret the number as a little
 endian value;
diff --git a/src/apprentice.c b/src/apprentice.c
index 8793982e..cd8250b1 100644
--- a/src/apprentice.c
+++ b/src/apprentice.c
@@ -32,7 +32,7 @@
 #include "file.h"
 
 #ifndef	lint
-FILE_RCSID("@(#)$File: apprentice.c,v 1.250 2016/07/05 19:20:19 christos Exp $")
+FILE_RCSID("@(#)$File: apprentice.c,v 1.251 2016/07/20 11:27:08 christos Exp $")
 #endif	/* lint */
 
 #include "magic.h"
@@ -1881,10 +1881,13 @@ parse(struct magic_set *ms, struct magic_entry *me, const char *line,
 	if (m->flag & INDIR) {
 		m->in_type = FILE_LONG;
 		m->in_offset = 0;
+		m->in_op = 0;
 		/*
-		 * read [.lbs][+-]nnnnn)
+		 * read [.,lbs][+-]nnnnn)
 		 */
-		if (*l == '.') {
+		if (*l == '.' || *l == ',') {
+			if (*l == ',')
+				m->in_op |= FILE_OPSIGNED;
 			l++;
 			switch (*l) {
 			case 'l':
@@ -1936,7 +1939,6 @@ parse(struct magic_set *ms, struct magic_entry *me, const char *line,
 			l++;
 		}
 
-		m->in_op = 0;
 		if (*l == '~') {
 			m->in_op |= FILE_OPINVERSE;
 			l++;
diff --git a/src/file.h b/src/file.h
index 641bde7f..180efd35 100644
--- a/src/file.h
+++ b/src/file.h
@@ -27,7 +27,7 @@
  */
 /*
  * file.h - definitions for file(1) program
- * @(#)$File: file.h,v 1.179 2016/07/05 19:20:19 christos Exp $
+ * @(#)$File: file.h,v 1.180 2016/07/20 11:27:08 christos Exp $
  */
 
 #ifndef __file_h__
@@ -275,7 +275,7 @@ struct magic {
 #define				FILE_OPS_MASK	0x07 /* mask for above ops */
 #define				FILE_UNUSED_1	0x08
 #define				FILE_UNUSED_2	0x10
-#define				FILE_UNUSED_3	0x20
+#define				FILE_OPSIGNED	0x20
 #define				FILE_OPINVERSE	0x40
 #define				FILE_OPINDIRECT	0x80
 
diff --git a/src/softmagic.c b/src/softmagic.c
index 9f8b0bb6..80b02461 100644
--- a/src/softmagic.c
+++ b/src/softmagic.c
@@ -32,7 +32,7 @@
 #include "file.h"
 
 #ifndef	lint
-FILE_RCSID("@(#)$File: softmagic.c,v 1.235 2016/06/14 00:22:36 christos Exp $")
+FILE_RCSID("@(#)$File: softmagic.c,v 1.236 2016/07/20 11:27:08 christos Exp $")
 #endif	/* lint */
 
 #include "magic.h"
@@ -63,7 +63,7 @@ private int cvt_16(union VALUETYPE *, const struct magic *);
 private int cvt_32(union VALUETYPE *, const struct magic *);
 private int cvt_64(union VALUETYPE *, const struct magic *);
 
-#define OFFSET_OOB(n, o, i)	((n) < (o) || (i) > ((n) - (o)))
+#define OFFSET_OOB(n, o, i)	((n) < (uint32_t)(o) || (i) > ((n) - (o)))
 #define BE64(p) (((uint64_t)(p)->hq[0]<<56)|((uint64_t)(p)->hq[1]<<48)| \
     ((uint64_t)(p)->hq[2]<<40)|((uint64_t)(p)->hq[3]<<32)| \
     ((uint64_t)(p)->hq[4]<<24)|((uint64_t)(p)->hq[5]<<16)| \
@@ -80,6 +80,7 @@ private int cvt_64(union VALUETYPE *, const struct magic *);
      ((uint32_t)(p)->hl[3]<<8)|((uint32_t)(p)->hl[2]))
 #define BE16(p) (((uint16_t)(p)->hs[0]<<8)|((uint16_t)(p)->hs[1]))
 #define LE16(p) (((uint16_t)(p)->hs[1]<<8)|((uint16_t)(p)->hs[0]))
+#define SEXT(s,v,p) ((s)?(intmax_t)(int##v##_t)(p):(intmax_t)(uint##v##_t)(p))
 
 /*
  * softmagic - lookup one file in parsed, in-memory copy of database
@@ -1294,6 +1295,45 @@ mcopy(struct magic_set *ms, union VALUETYPE *p, int type, int indir,
 	return 0;
 }
 
+private uint32_t
+do_ops(struct magic *m, intmax_t lhs, intmax_t off)
+{
+	intmax_t offset;
+	if (off) {
+		switch (m->in_op & FILE_OPS_MASK) {
+		case FILE_OPAND:
+			offset = lhs & off;
+			break;
+		case FILE_OPOR:
+			offset = lhs | off;
+			break;
+		case FILE_OPXOR:
+			offset = lhs ^ off;
+			break;
+		case FILE_OPADD:
+			offset = lhs + off;
+			break;
+		case FILE_OPMINUS:
+			offset = lhs - off;
+			break;
+		case FILE_OPMULTIPLY:
+			offset = lhs * off;
+			break;
+		case FILE_OPDIVIDE:
+			offset = lhs / off;
+			break;
+		case FILE_OPMODULO:
+			offset = lhs % off;
+			break;
+		}
+	} else
+		offset = lhs;
+	if (m->in_op & FILE_OPINVERSE)
+		offset = ~offset;
+
+	return (uint32_t)offset;
+}
+
 private int
 mget(struct magic_set *ms, const unsigned char *s, struct magic *m,
     size_t nbytes, size_t o, unsigned int cont_level, int mode, int text,
@@ -1301,7 +1341,7 @@ mget(struct magic_set *ms, const unsigned char *s, struct magic *m,
     int *printed_something, int *need_separator, int *returnval)
 {
 	uint32_t offset = ms->offset;
-	uint32_t lhs;
+	intmax_t lhs;
 	file_pushbuf_t *pb;
 	int rv, oneed_separator, in_type;
 	char *rbuf;
@@ -1337,7 +1377,8 @@ mget(struct magic_set *ms, const unsigned char *s, struct magic *m,
 	}
 
 	if (m->flag & INDIR) {
-		int off = m->in_offset;
+		intmax_t off = m->in_offset;
+		const int sgn = m->in_op & FILE_OPSIGNED;
 		if (m->in_op & FILE_OPINDIRECT) {
 			const union VALUETYPE *q = CAST(const union VALUETYPE *,
 			    ((const void *)(s + offset + off)));
@@ -1345,178 +1386,55 @@ mget(struct magic_set *ms, const unsigned char *s, struct magic *m,
 				return 0;
 			switch (cvt_flip(m->in_type, flip)) {
 			case FILE_BYTE:
-				off = q->b;
+				off = SEXT(sgn,8,q->b);
 				break;
 			case FILE_SHORT:
-				off = q->h;
+				off = SEXT(sgn,16,q->h);
 				break;
 			case FILE_BESHORT:
-				off = (short)BE16(q);
+				off = SEXT(sgn,16,BE16(q));
 				break;
 			case FILE_LESHORT:
-				off = (short)LE16(q);
+				off = SEXT(sgn,16,LE16(q));
 				break;
 			case FILE_LONG:
-				off = q->l;
+				off = SEXT(sgn,32,q->l);
 				break;
 			case FILE_BELONG:
 			case FILE_BEID3:
-				off = (int32_t)BE32(q);
+				off = SEXT(sgn,32,BE32(q));
 				break;
 			case FILE_LEID3:
 			case FILE_LELONG:
-				off = (int32_t)LE32(q);
+				off = SEXT(sgn,32,LE32(q));
 				break;
 			case FILE_MELONG:
-				off = (int32_t)ME32(q);
+				off = SEXT(sgn,32,ME32(q));
 				break;
 			}
 			if ((ms->flags & MAGIC_DEBUG) != 0)
-				fprintf(stderr, "indirect offs=%u\n", off);
+				fprintf(stderr, "indirect offs=%jd\n", off);
 		}
 		switch (in_type = cvt_flip(m->in_type, flip)) {
 		case FILE_BYTE:
 			if (OFFSET_OOB(nbytes, offset, 1))
 				return 0;
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = p->b & off;
-					break;
-				case FILE_OPOR:
-					offset = p->b | off;
-					break;
-				case FILE_OPXOR:
-					offset = p->b ^ off;
-					break;
-				case FILE_OPADD:
-					offset = p->b + off;
-					break;
-				case FILE_OPMINUS:
-					offset = p->b - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = p->b * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = p->b / off;
-					break;
-				case FILE_OPMODULO:
-					offset = p->b % off;
-					break;
-				}
-			} else
-				offset = p->b;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+			offset = do_ops(m, SEXT(sgn,8,p->b), off);
 			break;
 		case FILE_BESHORT:
 			if (OFFSET_OOB(nbytes, offset, 2))
 				return 0;
-			lhs = (p->hs[0] << 8) | p->hs[1];
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = lhs & off;
-					break;
-				case FILE_OPOR:
-					offset = lhs | off;
-					break;
-				case FILE_OPXOR:
-					offset = lhs ^ off;
-					break;
-				case FILE_OPADD:
-					offset = lhs + off;
-					break;
-				case FILE_OPMINUS:
-					offset = lhs - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = lhs * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = lhs / off;
-					break;
-				case FILE_OPMODULO:
-					offset = lhs % off;
-					break;
-				}
-			} else
-				offset = lhs;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+			offset = do_ops(m, SEXT(sgn,16,BE16(p)), off);
 			break;
 		case FILE_LESHORT:
 			if (OFFSET_OOB(nbytes, offset, 2))
 				return 0;
-			lhs = (p->hs[1] << 8) | p->hs[0];
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = lhs & off;
-					break;
-				case FILE_OPOR:
-					offset = lhs | off;
-					break;
-				case FILE_OPXOR:
-					offset = lhs ^ off;
-					break;
-				case FILE_OPADD:
-					offset = lhs + off;
-					break;
-				case FILE_OPMINUS:
-					offset = lhs - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = lhs * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = lhs / off;
-					break;
-				case FILE_OPMODULO:
-					offset = lhs % off;
-					break;
-				}
-			} else
-				offset = lhs;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+			offset = do_ops(m, SEXT(sgn,16,LE16(p)), off);
 			break;
 		case FILE_SHORT:
 			if (OFFSET_OOB(nbytes, offset, 2))
 				return 0;
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = p->h & off;
-					break;
-				case FILE_OPOR:
-					offset = p->h | off;
-					break;
-				case FILE_OPXOR:
-					offset = p->h ^ off;
-					break;
-				case FILE_OPADD:
-					offset = p->h + off;
-					break;
-				case FILE_OPMINUS:
-					offset = p->h - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = p->h * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = p->h / off;
-					break;
-				case FILE_OPMODULO:
-					offset = p->h % off;
-					break;
-				}
-			}
-			else
-				offset = p->h;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+			offset = do_ops(m, SEXT(sgn,16,p->h), off);
 			break;
 		case FILE_BELONG:
 		case FILE_BEID3:
@@ -1524,38 +1442,8 @@ mget(struct magic_set *ms, const unsigned char *s, struct magic *m,
 				return 0;
 			lhs = BE32(p);
 			if (in_type == FILE_BEID3)
-				lhs = cvt_id3(ms, lhs);
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = lhs & off;
-					break;
-				case FILE_OPOR:
-					offset = lhs | off;
-					break;
-				case FILE_OPXOR:
-					offset = lhs ^ off;
-					break;
-				case FILE_OPADD:
-					offset = lhs + off;
-					break;
-				case FILE_OPMINUS:
-					offset = lhs - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = lhs * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = lhs / off;
-					break;
-				case FILE_OPMODULO:
-					offset = lhs % off;
-					break;
-				}
-			} else
-				offset = lhs;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+				lhs = cvt_id3(ms, (uint32_t)lhs);
+			offset = do_ops(m, SEXT(sgn,32,lhs), off);
 			break;
 		case FILE_LELONG:
 		case FILE_LEID3:
@@ -1563,109 +1451,18 @@ mget(struct magic_set *ms, const unsigned char *s, struct magic *m,
 				return 0;
 			lhs = LE32(p);
 			if (in_type == FILE_LEID3)
-				lhs = cvt_id3(ms, lhs);
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = lhs & off;
-					break;
-				case FILE_OPOR:
-					offset = lhs | off;
-					break;
-				case FILE_OPXOR:
-					offset = lhs ^ off;
-					break;
-				case FILE_OPADD:
-					offset = lhs + off;
-					break;
-				case FILE_OPMINUS:
-					offset = lhs - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = lhs * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = lhs / off;
-					break;
-				case FILE_OPMODULO:
-					offset = lhs % off;
-					break;
-				}
-			} else
-				offset = lhs;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+				lhs = cvt_id3(ms, (uint32_t)lhs);
+			offset = do_ops(m, SEXT(sgn,32,lhs), off);
 			break;
 		case FILE_MELONG:
 			if (OFFSET_OOB(nbytes, offset, 4))
 				return 0;
-			lhs = ME32(p);
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = lhs & off;
-					break;
-				case FILE_OPOR:
-					offset = lhs | off;
-					break;
-				case FILE_OPXOR:
-					offset = lhs ^ off;
-					break;
-				case FILE_OPADD:
-					offset = lhs + off;
-					break;
-				case FILE_OPMINUS:
-					offset = lhs - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = lhs * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = lhs / off;
-					break;
-				case FILE_OPMODULO:
-					offset = lhs % off;
-					break;
-				}
-			} else
-				offset = lhs;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+			offset = do_ops(m, SEXT(sgn,32,ME32(p)), off);
 			break;
 		case FILE_LONG:
 			if (OFFSET_OOB(nbytes, offset, 4))
 				return 0;
-			if (off) {
-				switch (m->in_op & FILE_OPS_MASK) {
-				case FILE_OPAND:
-					offset = p->l & off;
-					break;
-				case FILE_OPOR:
-					offset = p->l | off;
-					break;
-				case FILE_OPXOR:
-					offset = p->l ^ off;
-					break;
-				case FILE_OPADD:
-					offset = p->l + off;
-					break;
-				case FILE_OPMINUS:
-					offset = p->l - off;
-					break;
-				case FILE_OPMULTIPLY:
-					offset = p->l * off;
-					break;
-				case FILE_OPDIVIDE:
-					offset = p->l / off;
-					break;
-				case FILE_OPMODULO:
-					offset = p->l % off;
-					break;
-				}
-			} else
-				offset = p->l;
-			if (m->in_op & FILE_OPINVERSE)
-				offset = ~offset;
+			offset = do_ops(m, SEXT(sgn,32,p->l), off);
 			break;
 		default:
 			break;