From 84c5e0dd2e7344d36d5c3a32228b35a284ef1a1a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 1 Apr 2021 13:34:16 -0400 Subject: [PATCH] Fix pg_restore's misdesigned code for detecting archive file format. Despite the clear comments pointing out that the duplicative code segments in ReadHead() and _discoverArchiveFormat() needed to be in sync, they were not: the latter did not bother to apply any of the sanity checks in the former. We'd missed noticing this partly because none of those checks would fail in scenarios we customarily test, and partly because the oversight would be masked if both segments execute, which they would in cases other than needing to autodetect the format of a non-seekable stdin source. However, in a case meeting all these requirements --- for example, trying to read a newer-than-supported archive format from non-seekable stdin --- pg_restore missed applying the version check and would likely dump core or otherwise misbehave. The whole thing is silly anyway, because there seems little reason to duplicate the logic beyond the one-line verification that the file starts with "PGDMP". There seems to have been an undocumented assumption that multiple major formats (major enough to require separate reader modules) would nonetheless share the first half-dozen fields of the custom-format header. This seems unlikely, so let's fix it by just nuking the duplicate logic in _discoverArchiveFormat(). Also get rid of the pointless attempt to seek back to the start of the file after successful autodetection. That wastes cycles and it means we have four behaviors to verify not two. Per bug #16951 from Sergey Koposov. This has been broken for decades, so back-patch to all supported versions. Discussion: https://postgr.es/m/16951-a4dd68cf0de23048@postgresql.org --- src/bin/pg_dump/pg_backup_archiver.c | 153 ++++++++------------------- src/bin/pg_dump/pg_backup_archiver.h | 18 ++-- src/bin/pg_dump/pg_backup_tar.c | 6 -- 3 files changed, 59 insertions(+), 118 deletions(-) diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c index 5b9fbe89d0..068e86f436 100644 --- a/src/bin/pg_dump/pg_backup_archiver.c +++ b/src/bin/pg_dump/pg_backup_archiver.c @@ -2086,6 +2086,7 @@ _discoverArchiveFormat(ArchiveHandle *AH) if (AH->lookahead) free(AH->lookahead); + AH->readHeader = 0; AH->lookaheadSize = 512; AH->lookahead = pg_malloc0(512); AH->lookaheadLen = 0; @@ -2157,62 +2158,9 @@ _discoverArchiveFormat(ArchiveHandle *AH) if (strncmp(sig, "PGDMP", 5) == 0) { - int byteread; - char vmaj, - vmin, - vrev; - - /* - * Finish reading (most of) a custom-format header. - * - * NB: this code must agree with ReadHead(). - */ - if ((byteread = fgetc(fh)) == EOF) - READ_ERROR_EXIT(fh); - - vmaj = byteread; - - if ((byteread = fgetc(fh)) == EOF) - READ_ERROR_EXIT(fh); - - vmin = byteread; - - /* Save these too... */ - AH->lookahead[AH->lookaheadLen++] = vmaj; - AH->lookahead[AH->lookaheadLen++] = vmin; - - /* Check header version; varies from V1.0 */ - if (vmaj > 1 || (vmaj == 1 && vmin > 0)) /* Version > 1.0 */ - { - if ((byteread = fgetc(fh)) == EOF) - READ_ERROR_EXIT(fh); - - vrev = byteread; - AH->lookahead[AH->lookaheadLen++] = vrev; - } - else - vrev = 0; - - AH->version = MAKE_ARCHIVE_VERSION(vmaj, vmin, vrev); - - if ((AH->intSize = fgetc(fh)) == EOF) - READ_ERROR_EXIT(fh); - AH->lookahead[AH->lookaheadLen++] = AH->intSize; - - if (AH->version >= K_VERS_1_7) - { - if ((AH->offSize = fgetc(fh)) == EOF) - READ_ERROR_EXIT(fh); - AH->lookahead[AH->lookaheadLen++] = AH->offSize; - } - else - AH->offSize = AH->intSize; - - if ((byteread = fgetc(fh)) == EOF) - READ_ERROR_EXIT(fh); - - AH->format = byteread; - AH->lookahead[AH->lookaheadLen++] = AH->format; + /* It's custom format, stop here */ + AH->format = archCustom; + AH->readHeader = 1; } else { @@ -2249,22 +2197,15 @@ _discoverArchiveFormat(ArchiveHandle *AH) AH->format = archTar; } - /* If we can't seek, then mark the header as read */ - if (fseeko(fh, 0, SEEK_SET) != 0) - { - /* - * NOTE: Formats that use the lookahead buffer can unset this in their - * Init routine. - */ - AH->readHeader = 1; - } - else - AH->lookaheadLen = 0; /* Don't bother since we've reset the file */ - - /* Close the file */ + /* Close the file if we opened it */ if (wantClose) + { if (fclose(fh) != 0) fatal("could not close input file: %m"); + /* Forget lookahead, since we'll re-read header after re-opening */ + AH->readHeader = 0; + AH->lookaheadLen = 0; + } return AH->format; } @@ -3773,7 +3714,9 @@ WriteHead(ArchiveHandle *AH) void ReadHead(ArchiveHandle *AH) { - char tmpMag[7]; + char vmaj, + vmin, + vrev; int fmt; struct tm crtm; @@ -3785,49 +3728,47 @@ ReadHead(ArchiveHandle *AH) */ if (!AH->readHeader) { - char vmaj, - vmin, - vrev; + char tmpMag[7]; AH->ReadBufPtr(AH, tmpMag, 5); if (strncmp(tmpMag, "PGDMP", 5) != 0) fatal("did not find magic string in file header"); - - vmaj = AH->ReadBytePtr(AH); - vmin = AH->ReadBytePtr(AH); - - if (vmaj > 1 || (vmaj == 1 && vmin > 0)) /* Version > 1.0 */ - vrev = AH->ReadBytePtr(AH); - else - vrev = 0; - - AH->version = MAKE_ARCHIVE_VERSION(vmaj, vmin, vrev); - - if (AH->version < K_VERS_1_0 || AH->version > K_VERS_MAX) - fatal("unsupported version (%d.%d) in file header", - vmaj, vmin); - - AH->intSize = AH->ReadBytePtr(AH); - if (AH->intSize > 32) - fatal("sanity check on integer size (%lu) failed", - (unsigned long) AH->intSize); - - if (AH->intSize > sizeof(int)) - pg_log_warning("archive was made on a machine with larger integers, some operations might fail"); - - if (AH->version >= K_VERS_1_7) - AH->offSize = AH->ReadBytePtr(AH); - else - AH->offSize = AH->intSize; - - fmt = AH->ReadBytePtr(AH); - - if (AH->format != fmt) - fatal("expected format (%d) differs from format found in file (%d)", - AH->format, fmt); } + vmaj = AH->ReadBytePtr(AH); + vmin = AH->ReadBytePtr(AH); + + if (vmaj > 1 || (vmaj == 1 && vmin > 0)) /* Version > 1.0 */ + vrev = AH->ReadBytePtr(AH); + else + vrev = 0; + + AH->version = MAKE_ARCHIVE_VERSION(vmaj, vmin, vrev); + + if (AH->version < K_VERS_1_0 || AH->version > K_VERS_MAX) + fatal("unsupported version (%d.%d) in file header", + vmaj, vmin); + + AH->intSize = AH->ReadBytePtr(AH); + if (AH->intSize > 32) + fatal("sanity check on integer size (%lu) failed", + (unsigned long) AH->intSize); + + if (AH->intSize > sizeof(int)) + pg_log_warning("archive was made on a machine with larger integers, some operations might fail"); + + if (AH->version >= K_VERS_1_7) + AH->offSize = AH->ReadBytePtr(AH); + else + AH->offSize = AH->intSize; + + fmt = AH->ReadBytePtr(AH); + + if (AH->format != fmt) + fatal("expected format (%d) differs from format found in file (%d)", + AH->format, fmt); + if (AH->version >= K_VERS_1_2) { if (AH->version < K_VERS_1_4) diff --git a/src/bin/pg_dump/pg_backup_archiver.h b/src/bin/pg_dump/pg_backup_archiver.h index 7201b60417..6426b9104b 100644 --- a/src/bin/pg_dump/pg_backup_archiver.h +++ b/src/bin/pg_dump/pg_backup_archiver.h @@ -258,15 +258,21 @@ struct _archiveHandle time_t createDate; /* Date archive created */ /* - * Fields used when discovering header. A format can always get the - * previous read bytes from here... + * Fields used when discovering archive format. For tar format, we load + * the first block into the lookahead buffer, and verify that it looks + * like a tar header. The tar module must then consume bytes from the + * lookahead buffer before reading any more from the file. For custom + * format, we load only the "PGDMP" marker into the buffer, and then set + * readHeader after confirming it matches. The buffer is vestigial in + * this case, as the subsequent code just checks readHeader and doesn't + * examine the buffer. */ - int readHeader; /* Used if file header has been read already */ + int readHeader; /* Set if we already read "PGDMP" marker */ char *lookahead; /* Buffer used when reading header to discover * format */ - size_t lookaheadSize; /* Size of allocated buffer */ - size_t lookaheadLen; /* Length of data in lookahead */ - pgoff_t lookaheadPos; /* Current read position in lookahead buffer */ + size_t lookaheadSize; /* Allocated size of buffer */ + size_t lookaheadLen; /* Length of valid data in lookahead */ + size_t lookaheadPos; /* Current read position in lookahead buffer */ ArchiveEntryPtrType ArchiveEntryPtr; /* Called for each metadata object */ StartDataPtrType StartDataPtr; /* Called when table data is about to be diff --git a/src/bin/pg_dump/pg_backup_tar.c b/src/bin/pg_dump/pg_backup_tar.c index a6acd85f60..7e7625a39d 100644 --- a/src/bin/pg_dump/pg_backup_tar.c +++ b/src/bin/pg_dump/pg_backup_tar.c @@ -228,12 +228,6 @@ InitArchiveFmt_Tar(ArchiveHandle *AH) ctx->hasSeek = checkSeek(ctx->tarFH); - /* - * Forcibly unmark the header as read since we use the lookahead - * buffer - */ - AH->readHeader = 0; - ctx->FH = (void *) tarOpen(AH, "toc.dat", 'r'); ReadHead(AH); ReadToc(AH);