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Fix tar files emitted by pg_dump and pg_basebackup to be POSIX conformant.

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Both programs got the "magic" string wrong, causing standard-conforming tar
implementations to believe the output was just legacy tar format without
any POSIX extensions.  This doesn't actually matter that much, especially
since pg_dump failed to fill the POSIX fields anyway, but still there is
little point in emitting tar format if we can't be compliant with the
standard.  In addition, pg_dump failed to write the EOF marker correctly
(there should be 2 blocks of zeroes not just one), pg_basebackup put the
numeric group ID in the wrong place, and both programs had a pretty
brain-dead idea of how to compute the checksum.  Fix all that and improve
the comments a bit.

pg_restore is modified to accept either the correct POSIX-compliant "magic"
string or the previous value.  This part of the change will need to be
back-patched to avoid an unnecessary compatibility break when a previous
version tries to read tar-format output from 9.3 pg_dump.

Brian Weaver and Tom Lane
This commit is contained in:
Tom Lane
2012-09-28 15:19:15 -04:00
parent edc9109c42
commit 05b555d12b
4 changed files with 110 additions and 69 deletions
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87
src/bin/pg_dump/pg_backup_tar.c
View File

@@ -882,8 +882,10 @@ _CloseArchive(ArchiveHandle *AH)
tarClose(AH, th);
/* Add a block of NULLs since it's de-rigeur. */
for (i = 0; i < 512; i++)
/*
* EOF marker for tar files is two blocks of NULLs.
*/
for (i = 0; i < 512 * 2; i++)
{
if (fputc(0, ctx->tarFH) == EOF)
exit_horribly(modulename,
@@ -1032,11 +1034,16 @@ _tarChecksum(char *header)
int i,
sum;
sum = 0;
/*
* Per POSIX, the checksum is the simple sum of all bytes in the header,
* treating the bytes as unsigned, and treating the checksum field (at
* offset 148) as though it contained 8 spaces.
*/
sum = 8 * ' '; /* presumed value for checksum field */
for (i = 0; i < 512; i++)
if (i < 148 || i >= 156)
sum += 0xFF & header[i];
return sum + 256; /* Assume 8 blanks in checksum field */
return sum;
}
bool
@@ -1050,11 +1057,15 @@ isValidTarHeader(char *header)
if (sum != chk)
return false;
/* POSIX format */
if (strncmp(&header[257], "ustar00", 7) == 0)
/* POSIX tar format */
if (memcmp(&header[257], "ustar\0", 6) == 0 &&
memcmp(&header[263], "00", 2) == 0)
return true;
/* older format */
if (strncmp(&header[257], "ustar ", 7) == 0)
/* GNU tar format */
if (memcmp(&header[257], "ustar \0", 8) == 0)
return true;
/* not-quite-POSIX format written by pre-9.3 pg_dump */
if (memcmp(&header[257], "ustar00\0", 8) == 0)
return true;
return false;
@@ -1329,63 +1340,71 @@ static void
_tarWriteHeader(TAR_MEMBER *th)
{
char h[512];
int lastSum = 0;
int sum;
/*
* Note: most of the fields in a tar header are not supposed to be
* null-terminated. We use sprintf, which will write a null after the
* required bytes; that null goes into the first byte of the next field.
* This is okay as long as we fill the fields in order.
*/
memset(h, 0, sizeof(h));
/* Name 100 */
sprintf(&h[0], "%.99s", th->targetFile);
/* Mode 8 */
sprintf(&h[100], "100600 ");
sprintf(&h[100], "0000600 ");
/* User ID 8 */
sprintf(&h[108], "004000 ");
sprintf(&h[108], "0004000 ");
/* Group 8 */
sprintf(&h[116], "002000 ");
sprintf(&h[116], "0002000 ");
/* File size 12 - 11 digits, 1 space, no NUL */
/* File size 12 - 11 digits, 1 space; use print_val for 64 bit support */
print_val(&h[124], th->fileLen, 8, 11);
sprintf(&h[135], " ");
/* Mod Time 12 */
sprintf(&h[136], "%011o ", (int) time(NULL));
/* Checksum 8 */
sprintf(&h[148], "%06o ", lastSum);
/* Checksum 8 cannot be calculated until we've filled all other fields */
/* Type - regular file */
sprintf(&h[156], "0");
/* Link tag 100 (NULL) */
/* Link Name 100 (leave as nulls) */
/* Magic 6 + Version 2 */
sprintf(&h[257], "ustar00");
/* Magic 6 */
sprintf(&h[257], "ustar");
/* Version 2 */
sprintf(&h[263], "00");
#if 0
/* User 32 */
sprintf(&h[265], "%.31s", ""); /* How do I get username reliably? Do
* I need to? */
/* XXX: Do we need to care about setting correct username? */
sprintf(&h[265], "%.31s", "postgres");
/* Group 32 */
sprintf(&h[297], "%.31s", ""); /* How do I get group reliably? Do I
* need to? */
/* XXX: Do we need to care about setting correct group name? */
sprintf(&h[297], "%.31s", "postgres");
/* Maj Dev 8 */
sprintf(&h[329], "%6o ", 0);
/* Major Dev 8 */
sprintf(&h[329], "%07o ", 0);
/* Min Dev 8 */
sprintf(&h[337], "%6o ", 0);
#endif
/* Minor Dev 8 */
sprintf(&h[337], "%07o ", 0);
while ((sum = _tarChecksum(h)) != lastSum)
{
sprintf(&h[148], "%06o ", sum);
lastSum = sum;
}
/* Prefix 155 - not used, leave as nulls */
/*
* We mustn't overwrite the next field while inserting the checksum.
* Fortunately, the checksum can't exceed 6 octal digits, so we just write
* 6 digits, a space, and a null, which is legal per POSIX.
*/
sprintf(&h[148], "%06o ", _tarChecksum(h));
/* Now write the completed header. */
if (fwrite(h, 1, 512, th->tarFH) != 512)
exit_horribly(modulename, "could not write to output file: %s\n", strerror(errno));
}