gunzip: fix incorrect decoding of "fixed" inflate blocks

function                                             old     new   delta
huft_build                                          1008    1022     +14
inflate_block                                       1253    1256      +3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 17/0)               Total: 17 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/archival/libarchive/decompress_gunzip.c b/archival/libarchive/decompress_gunzip.c
index 0f8173d0ad982277217526998f6f812e36bc4bc9..03049cc9b4c7387e35b78c73295649da5718eb0d 100644 (file)
--- a/archival/libarchive/decompress_gunzip.c
+++ b/archival/libarchive/decompress_gunzip.c
@@ -280,11 +280,17 @@ static unsigned fill_bitbuffer(STATE_PARAM unsigned bitbuffer, unsigned *current
  * b:  code lengths in bits (all assumed <= BMAX)
  * n:  number of codes (assumed <= N_MAX)
  * s:  number of simple-valued codes (0..s-1)
- * d:  list of base values for non-simple codes
- * e:  list of extra bits for non-simple codes
+ * cp_ext->cp,ext: list of base values/extra bits for non-simple codes
  * m:  maximum lookup bits, returns actual
  * result: starting table
+ *
+ * On error, returns a value with lowest-bit set on error.
+ * It can be just the value of 0x1,
+ * or a valid pointer to a Huffman table, ORed with 0x1 if incompete table
+ * is given: "fixed inflate" decoder feeds us such data.
  */
+#define BAD_HUFT(p) ((uintptr_t)(p) & 1)
+#define ERR_RET     ((huft_t*)(uintptr_t)1)
 static huft_t* huft_build(const unsigned *b, const unsigned n,
                        const unsigned s, const struct cp_ext *cp_ext,
                        unsigned *m)
@@ -347,11 +353,11 @@ static huft_t* huft_build(const unsigned *b, const unsigned n,
        for (y = 1 << j; j < i; j++, y <<= 1) {
                y -= c[j];
                if (y < 0)
-                       return NULL; /* bad input: more codes than bits */
+                       return ERR_RET; /* bad input: more codes than bits */
        }
        y -= c[i];
        if (y < 0)
-               return NULL;
+               return ERR_RET;
        c[i] += y;
 
        /* Generate starting offsets into the value table for each length */
@@ -378,7 +384,7 @@ static huft_t* huft_build(const unsigned *b, const unsigned n,
        } while (++i < n);
 
        /* Generate the Huffman codes and for each, make the table entries */
-       result = NULL;
+       result = ERR_RET;
        t = &result;
        x[0] = i = 0;   /* first Huffman code is zero */
        p = v;          /* grab values in bit order */
@@ -472,7 +478,8 @@ static huft_t* huft_build(const unsigned *b, const unsigned n,
        *m = ws[1];
 
        if (y != 0 && g != 1) /* we were given an incomplete table */
-               return NULL;
+               /* return "result" ORed with 1 */
+               return (void*)((uintptr_t)result | 1);
 
        return result;
 }
@@ -776,13 +783,16 @@ static int inflate_block(STATE_PARAM smallint *e)
                        ll[i] = 8;
                bl = 7;
                inflate_codes_tl = huft_build(ll, 288, 257, &lit, &bl);
-               /* huft_build() never returns error here - we use known data */
+               /* ^^^ never returns error here - we use known data */
 
                /* set up distance table */
                for (i = 0; i < 30; i++) /* make an incomplete code set */
                        ll[i] = 5;
                bd = 5;
                inflate_codes_td = huft_build(ll, 30, 0, &dist, &bd);
+               /* ^^^ does return error here! (lsb bit is set) - we gave it incomplete code set */
+               /* clearing error bit: */
+               inflate_codes_td = (void*)((uintptr_t)inflate_codes_td & ~(uintptr_t)1);
 
                /* set up data for inflate_codes() */
                inflate_codes_setup(PASS_STATE bl, bd);
@@ -849,7 +859,7 @@ static int inflate_block(STATE_PARAM smallint *e)
                /* build decoding table for trees - single level, 7 bit lookup */
                bl = 7;
                inflate_codes_tl = huft_build(ll, 19, 19, NULL, &bl);
-               if (!inflate_codes_tl) {
+               if (BAD_HUFT(inflate_codes_tl)) {
                        abort_unzip(PASS_STATE_ONLY);   /* incomplete code set */
                }
 
@@ -914,12 +924,12 @@ static int inflate_block(STATE_PARAM smallint *e)
                /* build the decoding tables for literal/length and distance codes */
                bl = lbits;
                inflate_codes_tl = huft_build(ll, nl, 257, &lit, &bl);
-               if (!inflate_codes_tl) {
+               if (BAD_HUFT(inflate_codes_tl)) {
                        abort_unzip(PASS_STATE_ONLY);
                }
                bd = dbits;
                inflate_codes_td = huft_build(ll + nl, nd, 0, &dist, &bd);
-               if (!inflate_codes_td) {
+               if (BAD_HUFT(inflate_codes_td)) {
                        abort_unzip(PASS_STATE_ONLY);
                }