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gunzip: fix incorrect decoding of "fixed" inflate blocks

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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>
This commit is contained in:
Denys Vlasenko 2019-10-26 20:04:34 +02:00
parent 122a8cbd4a
commit caf5ee0dd9
1 changed files with 20 additions and 10 deletions
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30
archival/libarchive/decompress_gunzip.c
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@ -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);
}