CentOS Sources
2 changed files with 352 additions and 1 deletions
@ -0,0 +1,346 @@ |
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From 5c44459c3b28a9bd3283aaceab7c615f8020c531 Mon Sep 17 00:00:00 2001 |
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From: Mark Adler <madler@alumni.caltech.edu> |
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Date: Tue, 17 Apr 2018 22:09:22 -0700 |
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Subject: [PATCH] Fix a bug that can crash deflate on some input when using |
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Z_FIXED. |
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|
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This bug was reported by Danilo Ramos of Eideticom, Inc. It has |
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lain in wait 13 years before being found! The bug was introduced |
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in zlib 1.2.2.2, with the addition of the Z_FIXED option. That |
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option forces the use of fixed Huffman codes. For rare inputs with |
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a large number of distant matches, the pending buffer into which |
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the compressed data is written can overwrite the distance symbol |
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table which it overlays. That results in corrupted output due to |
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invalid distances, and can result in out-of-bound accesses, |
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crashing the application. |
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|
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The fix here combines the distance buffer and literal/length |
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buffers into a single symbol buffer. Now three bytes of pending |
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buffer space are opened up for each literal or length/distance |
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pair consumed, instead of the previous two bytes. This assures |
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that the pending buffer cannot overwrite the symbol table, since |
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the maximum fixed code compressed length/distance is 31 bits, and |
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since there are four bytes of pending space for every three bytes |
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of symbol space. |
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---
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deflate.c | 74 ++++++++++++++++++++++++++++++++++++++++--------------- |
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deflate.h | 25 +++++++++---------- |
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trees.c | 50 +++++++++++-------------------------- |
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3 files changed, 79 insertions(+), 70 deletions(-) |
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diff --git a/deflate.c b/deflate.c
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index 425babc..19cba87 100644
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--- a/deflate.c
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+++ b/deflate.c
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@@ -255,11 +255,6 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
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int wrap = 1; |
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static const char my_version[] = ZLIB_VERSION; |
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|
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- ushf *overlay;
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- /* We overlay pending_buf and d_buf+l_buf. This works since the average
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- * output size for (length,distance) codes is <= 24 bits.
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- */
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-
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if (version == Z_NULL || version[0] != my_version[0] || |
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stream_size != sizeof(z_stream)) { |
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return Z_VERSION_ERROR; |
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@@ -329,9 +324,47 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
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s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */ |
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|
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- overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
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- s->pending_buf = (uchf *) overlay;
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- s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
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+ /* We overlay pending_buf and sym_buf. This works since the average size
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+ * for length/distance pairs over any compressed block is assured to be 31
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+ * bits or less.
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+ *
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+ * Analysis: The longest fixed codes are a length code of 8 bits plus 5
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+ * extra bits, for lengths 131 to 257. The longest fixed distance codes are
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+ * 5 bits plus 13 extra bits, for distances 16385 to 32768. The longest
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+ * possible fixed-codes length/distance pair is then 31 bits total.
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+ *
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+ * sym_buf starts one-fourth of the way into pending_buf. So there are
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+ * three bytes in sym_buf for every four bytes in pending_buf. Each symbol
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+ * in sym_buf is three bytes -- two for the distance and one for the
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+ * literal/length. As each symbol is consumed, the pointer to the next
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+ * sym_buf value to read moves forward three bytes. From that symbol, up to
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+ * 31 bits are written to pending_buf. The closest the written pending_buf
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+ * bits gets to the next sym_buf symbol to read is just before the last
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+ * code is written. At that time, 31*(n-2) bits have been written, just
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+ * after 24*(n-2) bits have been consumed from sym_buf. sym_buf starts at
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+ * 8*n bits into pending_buf. (Note that the symbol buffer fills when n-1
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+ * symbols are written.) The closest the writing gets to what is unread is
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+ * then n+14 bits. Here n is lit_bufsize, which is 16384 by default, and
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+ * can range from 128 to 32768.
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+ *
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+ * Therefore, at a minimum, there are 142 bits of space between what is
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+ * written and what is read in the overlain buffers, so the symbols cannot
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+ * be overwritten by the compressed data. That space is actually 139 bits,
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+ * due to the three-bit fixed-code block header.
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+ *
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+ * That covers the case where either Z_FIXED is specified, forcing fixed
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+ * codes, or when the use of fixed codes is chosen, because that choice
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+ * results in a smaller compressed block than dynamic codes. That latter
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+ * condition then assures that the above analysis also covers all dynamic
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+ * blocks. A dynamic-code block will only be chosen to be emitted if it has
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+ * fewer bits than a fixed-code block would for the same set of symbols.
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+ * Therefore its average symbol length is assured to be less than 31. So
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+ * the compressed data for a dynamic block also cannot overwrite the
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+ * symbols from which it is being constructed.
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+ */
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+
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+ s->pending_buf = (uchf *) ZALLOC(strm, s->lit_bufsize, 4);
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+ s->pending_buf_size = (ulg)s->lit_bufsize * 4;
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if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL || |
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s->pending_buf == Z_NULL) { |
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@@ -340,8 +373,12 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
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deflateEnd (strm); |
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return Z_MEM_ERROR; |
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} |
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- s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
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- s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
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+ s->sym_buf = s->pending_buf + s->lit_bufsize;
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+ s->sym_end = (s->lit_bufsize - 1) * 3;
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+ /* We avoid equality with lit_bufsize*3 because of wraparound at 64K
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+ * on 16 bit machines and because stored blocks are restricted to
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+ * 64K-1 bytes.
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+ */
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s->level = level; |
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s->strategy = strategy; |
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@@ -552,7 +589,7 @@ int ZEXPORT deflatePrime (strm, bits, value)
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if (deflateStateCheck(strm)) return Z_STREAM_ERROR; |
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s = strm->state; |
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- if ((Bytef *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
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+ if (s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
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return Z_BUF_ERROR; |
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do { |
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put = Buf_size - s->bi_valid; |
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@@ -1113,7 +1150,6 @@ int ZEXPORT deflateCopy (dest, source)
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#else |
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deflate_state *ds; |
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deflate_state *ss; |
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- ushf *overlay;
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if (deflateStateCheck(source) || dest == Z_NULL) { |
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@@ -1133,8 +1169,7 @@ int ZEXPORT deflateCopy (dest, source)
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ds->window = (Bytef *) ZALLOC_WINDOW(dest, ds->w_size, 2*sizeof(Byte)); |
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ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos)); |
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ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos)); |
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- overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
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- ds->pending_buf = (uchf *) overlay;
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+ ds->pending_buf = (uchf *) ZALLOC(dest, ds->lit_bufsize, 4);
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if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL || |
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ds->pending_buf == Z_NULL) { |
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@@ -1148,8 +1183,7 @@ int ZEXPORT deflateCopy (dest, source)
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zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size); |
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ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf); |
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- ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
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- ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
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+ ds->sym_buf = ds->pending_buf + ds->lit_bufsize;
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ds->l_desc.dyn_tree = ds->dyn_ltree; |
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ds->d_desc.dyn_tree = ds->dyn_dtree; |
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@@ -1925,7 +1959,7 @@ local block_state deflate_fast(s, flush)
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FLUSH_BLOCK(s, 1); |
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return finish_done; |
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} |
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- if (s->last_lit)
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+ if (s->sym_next)
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FLUSH_BLOCK(s, 0); |
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return block_done; |
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} |
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@@ -2056,7 +2090,7 @@ local block_state deflate_slow(s, flush)
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FLUSH_BLOCK(s, 1); |
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return finish_done; |
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} |
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- if (s->last_lit)
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+ if (s->sym_next)
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FLUSH_BLOCK(s, 0); |
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return block_done; |
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} |
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@@ -2131,7 +2165,7 @@ local block_state deflate_rle(s, flush)
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FLUSH_BLOCK(s, 1); |
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return finish_done; |
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} |
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- if (s->last_lit)
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+ if (s->sym_next)
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FLUSH_BLOCK(s, 0); |
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return block_done; |
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} |
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@@ -2170,7 +2204,7 @@ local block_state deflate_huff(s, flush)
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FLUSH_BLOCK(s, 1); |
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return finish_done; |
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} |
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- if (s->last_lit)
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+ if (s->sym_next)
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FLUSH_BLOCK(s, 0); |
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return block_done; |
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} |
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diff --git a/deflate.h b/deflate.h
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index 23ecdd3..d4cf1a9 100644
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--- a/deflate.h
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+++ b/deflate.h
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@@ -217,7 +217,7 @@ typedef struct internal_state {
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/* Depth of each subtree used as tie breaker for trees of equal frequency |
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*/ |
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- uchf *l_buf; /* buffer for literals or lengths */
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+ uchf *sym_buf; /* buffer for distances and literals/lengths */
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uInt lit_bufsize; |
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/* Size of match buffer for literals/lengths. There are 4 reasons for |
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@@ -239,13 +239,8 @@ typedef struct internal_state {
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* - I can't count above 4 |
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*/ |
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- uInt last_lit; /* running index in l_buf */
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-
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- ushf *d_buf;
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- /* Buffer for distances. To simplify the code, d_buf and l_buf have
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- * the same number of elements. To use different lengths, an extra flag
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- * array would be necessary.
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- */
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+ uInt sym_next; /* running index in sym_buf */
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+ uInt sym_end; /* symbol table full when sym_next reaches this */
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ulg opt_len; /* bit length of current block with optimal trees */ |
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ulg static_len; /* bit length of current block with static trees */ |
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@@ -325,20 +320,22 @@ void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,
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# define _tr_tally_lit(s, c, flush) \ |
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{ uch cc = (c); \ |
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- s->d_buf[s->last_lit] = 0; \
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- s->l_buf[s->last_lit++] = cc; \
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+ s->sym_buf[s->sym_next++] = 0; \
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+ s->sym_buf[s->sym_next++] = 0; \
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+ s->sym_buf[s->sym_next++] = cc; \
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s->dyn_ltree[cc].Freq++; \ |
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- flush = (s->last_lit == s->lit_bufsize-1); \
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+ flush = (s->sym_next == s->sym_end); \
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} |
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# define _tr_tally_dist(s, distance, length, flush) \ |
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{ uch len = (uch)(length); \ |
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ush dist = (ush)(distance); \ |
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- s->d_buf[s->last_lit] = dist; \
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- s->l_buf[s->last_lit++] = len; \
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+ s->sym_buf[s->sym_next++] = dist; \
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+ s->sym_buf[s->sym_next++] = dist >> 8; \
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+ s->sym_buf[s->sym_next++] = len; \
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dist--; \ |
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s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \ |
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s->dyn_dtree[d_code(dist)].Freq++; \ |
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- flush = (s->last_lit == s->lit_bufsize-1); \
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+ flush = (s->sym_next == s->sym_end); \
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} |
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#else |
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# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c) |
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diff --git a/trees.c b/trees.c
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index 4f4a650..decaeb7 100644
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--- a/trees.c
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+++ b/trees.c
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@@ -416,7 +416,7 @@ local void init_block(s)
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s->dyn_ltree[END_BLOCK].Freq = 1; |
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s->opt_len = s->static_len = 0L; |
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- s->last_lit = s->matches = 0;
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+ s->sym_next = s->matches = 0;
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} |
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#define SMALLEST 1 |
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@@ -948,7 +948,7 @@ void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)
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Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ", |
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opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len, |
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- s->last_lit));
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+ s->sym_next / 3));
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if (static_lenb <= opt_lenb) opt_lenb = static_lenb; |
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@@ -1017,8 +1017,9 @@ int ZLIB_INTERNAL _tr_tally (s, dist, lc)
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unsigned dist; /* distance of matched string */ |
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unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */ |
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{ |
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- s->d_buf[s->last_lit] = (ush)dist;
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- s->l_buf[s->last_lit++] = (uch)lc;
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+ s->sym_buf[s->sym_next++] = dist;
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+ s->sym_buf[s->sym_next++] = dist >> 8;
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+ s->sym_buf[s->sym_next++] = lc;
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if (dist == 0) { |
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/* lc is the unmatched char */ |
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s->dyn_ltree[lc].Freq++; |
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@@ -1033,30 +1034,7 @@ int ZLIB_INTERNAL _tr_tally (s, dist, lc)
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s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++; |
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s->dyn_dtree[d_code(dist)].Freq++; |
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} |
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-
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-#ifdef TRUNCATE_BLOCK
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- /* Try to guess if it is profitable to stop the current block here */
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- if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
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- /* Compute an upper bound for the compressed length */
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- ulg out_length = (ulg)s->last_lit*8L;
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- ulg in_length = (ulg)((long)s->strstart - s->block_start);
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- int dcode;
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- for (dcode = 0; dcode < D_CODES; dcode++) {
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- out_length += (ulg)s->dyn_dtree[dcode].Freq *
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- (5L+extra_dbits[dcode]);
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- }
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- out_length >>= 3;
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- Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
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- s->last_lit, in_length, out_length,
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- 100L - out_length*100L/in_length));
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- if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
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- }
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-#endif
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- return (s->last_lit == s->lit_bufsize-1);
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- /* We avoid equality with lit_bufsize because of wraparound at 64K
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- * on 16 bit machines and because stored blocks are restricted to
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- * 64K-1 bytes.
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- */
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+ return (s->sym_next == s->sym_end);
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} |
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/* =========================================================================== |
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@@ -1069,13 +1047,14 @@ local void compress_block(s, ltree, dtree)
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{ |
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unsigned dist; /* distance of matched string */ |
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int lc; /* match length or unmatched char (if dist == 0) */ |
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- unsigned lx = 0; /* running index in l_buf */
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+ unsigned sx = 0; /* running index in sym_buf */
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unsigned code; /* the code to send */ |
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int extra; /* number of extra bits to send */ |
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- if (s->last_lit != 0) do {
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- dist = s->d_buf[lx];
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- lc = s->l_buf[lx++];
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+ if (s->sym_next != 0) do {
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+ dist = s->sym_buf[sx++] & 0xff;
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+ dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8;
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+ lc = s->sym_buf[sx++];
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if (dist == 0) { |
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send_code(s, lc, ltree); /* send a literal byte */ |
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Tracecv(isgraph(lc), (stderr," '%c' ", lc)); |
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@@ -1100,11 +1079,10 @@ local void compress_block(s, ltree, dtree)
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} |
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} /* literal or match pair ? */ |
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- /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
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- Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
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- "pendingBuf overflow");
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+ /* Check that the overlay between pending_buf and sym_buf is ok: */
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+ Assert(s->pending < s->lit_bufsize + sx, "pendingBuf overflow");
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- } while (lx < s->last_lit);
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+ } while (sx < s->sym_next);
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send_code(s, END_BLOCK, ltree); |
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} |
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--
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2.34.1 |
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|
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