Fix tar files emitted by pg_basebackup to be POSIX conformant.

Back-patch portions of commit 05b555d12bc2ad0d581f48a12b45174db41dc10d.
There doesn't seem to be any reason not to fix pg_basebackup fully, but
we can't change pg_dump's "magic" string without breaking older versions
of pg_restore.  Instead, just patch pg_restore to accept either version
of the magic string, in hopes of avoiding compatibility problems when
9.3 comes out.  I also fixed pg_dump to write the correct 2-block EOF
marker, since that won't create a compatibility problem with pg_restore
and it could help with some versions of tar.

Brian Weaver and Tom Lane

diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index e72556303abfd91d30229f4a027552c59f2a859e..3d72a162ebf9c28396796cbc69011d2a33e300d3 100644 (file)
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1759,9 +1759,11 @@ The commands accepted in walsender mode are:
       After the second regular result set, one or more CopyResponse results
       will be sent, one for PGDATA and one for each additional tablespace other
       than <literal>pg_default</> and <literal>pg_global</>. The data in
-      the CopyResponse results will be a tar format (using ustar00
-      extensions) dump of the tablespace contents. After the tar data is
-      complete, a final ordinary result set will be sent.
+      the CopyResponse results will be a tar format (following the
+      <quote>ustar interchange format</> specified in the POSIX 1003.1-2008
+      standard) dump of the tablespace contents, except that the two trailing
+      blocks of zeroes specified in the standard are omitted.
+      After the tar data is complete, a final ordinary result set will be sent.
      </para>
 
      <para>

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 0bc88a4040d6938c4619bb6ad9c42a6deea9a03e..1b234c64c9af3ad9013df86160e50552061744e4 100644 (file)
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -572,7 +572,7 @@ sendFileWithContent(const char *filename, const char *content)
 
 /*
  * Include all files from the given directory in the output tar stream. If
- * 'sizeonly' is true, we just calculate a total length and return ig, without
+ * 'sizeonly' is true, we just calculate a total length and return it, without
  * actually sending anything.
  */
 static int64
@@ -767,11 +767,16 @@ _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;
 }
 
 /* Given the member, write the TAR header & send the file */
@@ -850,9 +855,13 @@ _tarWriteHeader(const char *filename, const char *linktarget,
                struct stat * statbuf)
 {
    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 */
@@ -864,8 +873,11 @@ _tarWriteHeader(const char *filename, const char *linktarget,
         * indicated in the tar format by adding a slash at the end of the
         * name, the same as for regular directories.
         */
-       h[strlen(filename)] = '/';
-       h[strlen(filename) + 1] = '\0';
+       int         flen = strlen(filename);
+
+       flen = Min(flen, 99);
+       h[flen] = '/';
+       h[flen + 1] = '\0';
    }
 
    /* Mode 8 */
@@ -875,9 +887,9 @@ _tarWriteHeader(const char *filename, const char *linktarget,
    sprintf(&h[108], "%07o ", statbuf->st_uid);
 
    /* Group 8 */
-   sprintf(&h[117], "%07o ", statbuf->st_gid);
+   sprintf(&h[116], "%07o ", statbuf->st_gid);
 
-   /* File size 12 - 11 digits, 1 space, no NUL */
+   /* File size 12 - 11 digits, 1 space; use print_val for 64 bit support */
    if (linktarget != NULL || S_ISDIR(statbuf->st_mode))
        /* Symbolic link or directory has size zero */
        print_val(&h[124], 0, 8, 11);
@@ -888,13 +900,13 @@ _tarWriteHeader(const char *filename, const char *linktarget,
    /* Mod Time 12 */
    sprintf(&h[136], "%011o ", (int) statbuf->st_mtime);
 
-   /* Checksum 8 */
-   sprintf(&h[148], "%06o ", lastSum);
+   /* Checksum 8 cannot be calculated until we've filled all other fields */
 
    if (linktarget != NULL)
    {
        /* Type - Symbolic link */
        sprintf(&h[156], "2");
+       /* Link Name 100 */
        sprintf(&h[157], "%.99s", linktarget);
    }
    else if (S_ISDIR(statbuf->st_mode))
@@ -904,10 +916,11 @@ _tarWriteHeader(const char *filename, const char *linktarget,
        /* Type - regular file */
        sprintf(&h[156], "0");
 
-   /* Link tag 100 (NULL) */
+   /* Magic 6 */
+   sprintf(&h[257], "ustar");
 
-   /* Magic 6 + Version 2 */
-   sprintf(&h[257], "ustar00");
+   /* Version 2 */
+   sprintf(&h[263], "00");
 
    /* User 32 */
    /* XXX: Do we need to care about setting correct username? */
@@ -917,17 +930,21 @@ _tarWriteHeader(const char *filename, const char *linktarget,
    /* 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);
+   /* 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 send the completed header. */
    pq_putmessage('d', h, 512);
 }

diff --git a/src/bin/pg_dump/pg_backup_tar.c b/src/bin/pg_dump/pg_backup_tar.c
index ced5c13321e9ddaabb98ce275ec2b1e88b90f813..7da978fd97d28dba7fcecad4862c2a2baeb24088 100644 (file)
--- a/src/bin/pg_dump/pg_backup_tar.c
+++ b/src/bin/pg_dump/pg_backup_tar.c
@@ -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;
+   /* GNU tar format */
+   if (memcmp(&header[257], "ustar  \0", 8) == 0)
        return true;
-   /* older format */
-   if (strncmp(&header[257], "ustar  ", 7) == 0)
+   /* not-quite-POSIX format written by pre-9.3 pg_dump */
+   if (memcmp(&header[257], "ustar00\0", 8) == 0)
        return true;
 
    return false;