tar: support GNU 256-bit encoding in all numeric fields
function old new delta getOctal 63 125 +62 get_header_tar 1572 1496 -76 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 1/1 up/down: 62/-76) Total: -14 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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@ -18,87 +18,45 @@ typedef uint32_t aliased_uint32_t FIX_ALIASING;
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typedef off_t aliased_off_t FIX_ALIASING;
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typedef off_t aliased_off_t FIX_ALIASING;
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/*
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* GNU tar uses "base-256 encoding" for very large numbers (>8 billion).
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* Encoding is binary, with highest bit always set as a marker
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* and sign in next-highest bit:
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* 80 00 .. 00 - zero
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* bf ff .. ff - largest positive number
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* ff ff .. ff - minus 1
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* c0 00 .. 00 - smallest negative number
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*
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* We expect it only in size field, where negative numbers don't make sense.
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*/
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static off_t getBase256_len12(const char *str)
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{
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off_t value;
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int len;
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/* if (*str & 0x40) error; - caller prevents this */
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if (sizeof(off_t) >= 12) {
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/* Probably 128-bit (16 byte) off_t. Can be optimized. */
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len = 12;
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value = *str++ & 0x3f;
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while (--len)
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value = (value << 8) + (unsigned char) *str++;
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return value;
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}
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#ifdef CHECK_FOR_OVERFLOW
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/* Can be optimized to eat 32-bit chunks */
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char c = *str++ & 0x3f;
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len = 12;
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while (1) {
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if (c)
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bb_error_msg_and_die("overflow in base-256 encoded file size");
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if (--len == sizeof(off_t))
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break;
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c = *str++;
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}
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#else
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str += (12 - sizeof(off_t));
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#endif
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/* Now str points to sizeof(off_t) least significant bytes.
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*
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* Example of tar file with 8914993153 (0x213600001) byte file.
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* Field starts at offset 7c:
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* 00070 30 30 30 00 30 30 30 30 30 30 30 00 80 00 00 00 |000.0000000.....|
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* 00080 00 00 00 02 13 60 00 01 31 31 31 32 30 33 33 36 |.....`..11120336|
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*
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* str is at offset 80 or 84 now (64-bit or 32-bit off_t).
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* We (ab)use the fact that value happens to be aligned,
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* and fetch it in one go:
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*/
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if (sizeof(off_t) == 8) {
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value = *(aliased_off_t*)str;
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value = SWAP_BE64(value);
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} else if (sizeof(off_t) == 4) {
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value = *(aliased_off_t*)str;
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value = SWAP_BE32(value);
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} else {
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value = 0;
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len = sizeof(off_t);
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while (--len)
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value = (value << 8) + (unsigned char) *str++;
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}
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return value;
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}
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/* NB: _DESTROYS_ str[len] character! */
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/* NB: _DESTROYS_ str[len] character! */
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static unsigned long long getOctal(char *str, int len)
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static unsigned long long getOctal(char *str, int len)
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{
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{
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unsigned long long v;
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unsigned long long v;
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char *end;
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/* NB: leading spaces are allowed. Using strtoull to handle that.
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/* NB: leading spaces are allowed. Using strtoull to handle that.
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* The downside is that we accept e.g. "-123" too :(
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* The downside is that we accept e.g. "-123" too :(
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*/
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*/
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str[len] = '\0';
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str[len] = '\0';
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v = strtoull(str, &str, 8);
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v = strtoull(str, &end, 8);
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/* std: "Each numeric field is terminated by one or more
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/* std: "Each numeric field is terminated by one or more
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* <space> or NUL characters". We must support ' '! */
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* <space> or NUL characters". We must support ' '! */
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if (*str != '\0' && *str != ' ')
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if (*end != '\0' && *end != ' ') {
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bb_error_msg_and_die("corrupted octal value in tar header");
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int8_t first = str[0];
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if (!(first & 0x80))
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bb_error_msg_and_die("corrupted octal value in tar header");
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/*
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* GNU tar uses "base-256 encoding" for very large numbers.
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* Encoding is binary, with highest bit always set as a marker
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* and sign in next-highest bit:
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* 80 00 .. 00 - zero
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* bf ff .. ff - largest positive number
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* ff ff .. ff - minus 1
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* c0 00 .. 00 - smallest negative number
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*
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* Example of tar file with 8914993153 (0x213600001) byte file.
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* Field starts at offset 7c:
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* 00070 30 30 30 00 30 30 30 30 30 30 30 00 80 00 00 00 |000.0000000.....|
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* 00080 00 00 00 02 13 60 00 01 31 31 31 32 30 33 33 36 |.....`..11120336|
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*
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* NB: tarballs with NEGATIVE unix times encoded that way were seen!
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*/
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v = first;
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/* Sign-extend using 6th bit: */
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v <<= sizeof(unsigned long long)*8 - 7;
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v = (long long)v >> (sizeof(unsigned long long)*8 - 7);
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while (--len != 0)
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v = (v << 8) + (unsigned char) *str++;
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}
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return v;
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return v;
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}
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}
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#define GET_OCTAL(a) getOctal((a), sizeof(a))
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#define GET_OCTAL(a) getOctal((a), sizeof(a))
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@ -358,15 +316,8 @@ char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
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file_header->tar__uname = tar.uname[0] ? xstrndup(tar.uname, sizeof(tar.uname)) : NULL;
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file_header->tar__uname = tar.uname[0] ? xstrndup(tar.uname, sizeof(tar.uname)) : NULL;
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file_header->tar__gname = tar.gname[0] ? xstrndup(tar.gname, sizeof(tar.gname)) : NULL;
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file_header->tar__gname = tar.gname[0] ? xstrndup(tar.gname, sizeof(tar.gname)) : NULL;
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#endif
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#endif
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/* mtime: rudimentally handle GNU tar's "base256 encoding"
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file_header->mtime = GET_OCTAL(tar.mtime);
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* People report tarballs with NEGATIVE unix times encoded that way */
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file_header->size = GET_OCTAL(tar.size);
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file_header->mtime = (tar.mtime[0] & 0x80) /* base256? */
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? 0 /* bogus */
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: GET_OCTAL(tar.mtime);
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/* size: handle GNU tar's "base256 encoding" */
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file_header->size = (tar.size[0] & 0xc0) == 0x80 /* positive base256? */
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? getBase256_len12(tar.size)
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: GET_OCTAL(tar.size);
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file_header->gid = GET_OCTAL(tar.gid);
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file_header->gid = GET_OCTAL(tar.gid);
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file_header->uid = GET_OCTAL(tar.uid);
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file_header->uid = GET_OCTAL(tar.uid);
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/* Set bits 0-11 of the files mode */
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/* Set bits 0-11 of the files mode */
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