Add option to not compute or check check values.

The undocumented (except in these commit comments) function
inflateValidate(strm, check) can be called after an inflateInit(),
inflateInit2(), or inflateReset2() with check equal to zero to
turn off the check value (CRC-32 or Adler-32) computation and
comparison. Calling with check not equal to zero turns checking
back on. This should only be called immediately after the init or
reset function. inflateReset() does not change the state, so a
previous inflateValidate() setting will remain in effect.

This also turns off validation of the gzip header CRC when
present.

This should only be used when a zlib or gzip stream has already
been checked, and repeated decompressions of the same stream no
longer need to be validated.

diff --git a/inflate.c b/inflate.c
index 5a687a6973047a64885e2ac8b8de3a1a42b3942d..9ee84d07da4c06d7781d704671015bf028a89217 100644 (file)
--- a/inflate.c
+++ b/inflate.c
@@ -156,7 +156,7 @@ int windowBits;
         windowBits = -windowBits;
     }
     else {
-        wrap = (windowBits >> 4) + 1;
+        wrap = (windowBits >> 4) + 5;
 #ifdef GUNZIP
         if (windowBits < 48)
             windowBits &= 15;
@@ -701,14 +701,16 @@ int flush;
             }
             if (state->head != Z_NULL)
                 state->head->text = (int)((hold >> 8) & 1);
-            if (state->flags & 0x0200) CRC2(state->check, hold);
+            if ((state->flags & 0x0200) && (state->wrap & 4))
+                CRC2(state->check, hold);
             INITBITS();
             state->mode = TIME;
         case TIME:
             NEEDBITS(32);
             if (state->head != Z_NULL)
                 state->head->time = hold;
-            if (state->flags & 0x0200) CRC4(state->check, hold);
+            if ((state->flags & 0x0200) && (state->wrap & 4))
+                CRC4(state->check, hold);
             INITBITS();
             state->mode = OS;
         case OS:
@@ -717,7 +719,8 @@ int flush;
                 state->head->xflags = (int)(hold & 0xff);
                 state->head->os = (int)(hold >> 8);
             }
-            if (state->flags & 0x0200) CRC2(state->check, hold);
+            if ((state->flags & 0x0200) && (state->wrap & 4))
+                CRC2(state->check, hold);
             INITBITS();
             state->mode = EXLEN;
         case EXLEN:
@@ -726,7 +729,8 @@ int flush;
                 state->length = (unsigned)(hold);
                 if (state->head != Z_NULL)
                     state->head->extra_len = (unsigned)hold;
-                if (state->flags & 0x0200) CRC2(state->check, hold);
+                if ((state->flags & 0x0200) && (state->wrap & 4))
+                    CRC2(state->check, hold);
                 INITBITS();
             }
             else if (state->head != Z_NULL)
@@ -744,7 +748,7 @@ int flush;
                                 len + copy > state->head->extra_max ?
                                 state->head->extra_max - len : copy);
                     }
-                    if (state->flags & 0x0200)
+                    if ((state->flags & 0x0200) && (state->wrap & 4))
                         state->check = crc32(state->check, next, copy);
                     have -= copy;
                     next += copy;
@@ -765,7 +769,7 @@ int flush;
                             state->length < state->head->name_max)
                         state->head->name[state->length++] = len;
                 } while (len && copy < have);
-                if (state->flags & 0x0200)
+                if ((state->flags & 0x0200) && (state->wrap & 4))
                     state->check = crc32(state->check, next, copy);
                 have -= copy;
                 next += copy;
@@ -786,7 +790,7 @@ int flush;
                             state->length < state->head->comm_max)
                         state->head->comment[state->length++] = len;
                 } while (len && copy < have);
-                if (state->flags & 0x0200)
+                if ((state->flags & 0x0200) && (state->wrap & 4))
                     state->check = crc32(state->check, next, copy);
                 have -= copy;
                 next += copy;
@@ -798,7 +802,7 @@ int flush;
         case HCRC:
             if (state->flags & 0x0200) {
                 NEEDBITS(16);
-                if (hold != (state->check & 0xffff)) {
+                if ((state->wrap & 4) && hold != (state->check & 0xffff)) {
                     strm->msg = (char *)"header crc mismatch";
                     state->mode = BAD;
                     break;
@@ -1179,11 +1183,11 @@ int flush;
                 out -= left;
                 strm->total_out += out;
                 state->total += out;
-                if (out)
+                if ((state->wrap & 4) && out)
                     strm->adler = state->check =
                         UPDATE(state->check, put - out, out);
                 out = left;
-                if ((
+                if ((state->wrap & 4) && (
 #ifdef GUNZIP
                      state->flags ? hold :
 #endif
@@ -1242,7 +1246,7 @@ int flush;
     strm->total_in += in;
     strm->total_out += out;
     state->total += out;
-    if (state->wrap && out)
+    if ((state->wrap & 4) && out)
         strm->adler = state->check =
             UPDATE(state->check, strm->next_out - out, out);
     strm->data_type = state->bits + (state->last ? 64 : 0) +
@@ -1501,6 +1505,21 @@ int subvert;
 #endif
 }
 
+int ZEXPORT inflateValidate(strm, check)
+z_streamp strm;
+int check;
+{
+    struct inflate_state FAR *state;
+
+    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    state = (struct inflate_state FAR *)strm->state;
+    if (check)
+        state->wrap |= 4;
+    else
+        state->wrap &= ~4;
+    return Z_OK;
+}
+
 long ZEXPORT inflateMark(strm)
 z_streamp strm;
 {

diff --git a/inflate.h b/inflate.h
index fbc9a67656dd779f46817dc2c55974160e17a4b7..adbc775d5f461405cc33b292e5939c7e521a13b1 100644 (file)
--- a/inflate.h
+++ b/inflate.h
@@ -82,7 +82,8 @@ typedef enum {
 struct inflate_state {
     inflate_mode mode;          /* current inflate mode */
     int last;                   /* true if processing last block */
-    int wrap;                   /* bit 0 true for zlib, bit 1 true for gzip */
+    int wrap;                   /* bit 0 true for zlib, bit 1 true for gzip,
+                                   bit 2 true to validate check value */
     int havedict;               /* true if dictionary provided */
     int flags;                  /* gzip header method and flags (0 if zlib) */
     unsigned dmax;              /* zlib header max distance (INFLATE_STRICT) */

diff --git a/zlib.h b/zlib.h
index 66dc6006a75a54a4c7d6af387369878d78c93cfc..67cfd7e67d89146b33ab2a00561ca42a1325cee8 100644 (file)
--- a/zlib.h
+++ b/zlib.h
@@ -1769,6 +1769,7 @@ ZEXTERN const char   * ZEXPORT zError           OF((int));
 ZEXTERN int            ZEXPORT inflateSyncPoint OF((z_streamp));
 ZEXTERN const z_crc_t FAR * ZEXPORT get_crc_table    OF((void));
 ZEXTERN int            ZEXPORT inflateUndermine OF((z_streamp, int));
+ZEXTERN int            ZEXPORT inflateValidate OF((z_streamp, int));
 ZEXTERN int            ZEXPORT inflateResetKeep OF((z_streamp));
 ZEXTERN int            ZEXPORT deflateResetKeep OF((z_streamp));
 #if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(Z_SOLO)