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3b910d0c5e
If we receive a broken or malicious pack from a remote, we will feed it to index-pack. As index-pack processes the objects as a stream, reconstructing and hashing each object to get its name, it is not very susceptible to doing the wrong with bad data (it simply notices that the data is bogus and aborts). However, one question raised on the list is whether it could be susceptible to problems during the delta-resolution phase. In particular, can a cycle in the packfile deltas cause us to go into an infinite loop or cause any other problem? The answer is no. We cannot have a cycle of delta-base offsets, because they go only in one direction (the OFS_DELTA object mentions its base by an offset towards the beginning of the file, and we explicitly reject negative offsets). We can have a cycle of REF_DELTA objects, which refer to base objects by sha1 name. However, index-pack does not know these sha1 names ahead of time; it has to reconstruct the objects to get their names, and it cannot do so if there is a delta cycle (in other words, it does not even realize there is a cycle, but only that there are items that cannot be resolved). Even though we can reason out that index-pack should handle this fine, let's add a few tests to make sure it behaves correctly. Signed-off-by: Jeff King <peff@peff.net> Acked-by: Nicolas Pitre <nico@fluxnic.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
101 lines
2.5 KiB
Bash
101 lines
2.5 KiB
Bash
#!/bin/sh
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#
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# Support routines for hand-crafting weird or malicious packs.
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#
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# You can make a complete pack like:
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#
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# pack_header 2 >foo.pack &&
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# pack_obj e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 >>foo.pack &&
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# pack_obj e68fe8129b546b101aee9510c5328e7f21ca1d18 >>foo.pack &&
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# pack_trailer foo.pack
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# Print the big-endian 4-byte octal representation of $1
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uint32_octal () {
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n=$1
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printf '\%o' $(($n / 16777216)); n=$((n % 16777216))
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printf '\%o' $(($n / 65536)); n=$((n % 65536))
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printf '\%o' $(($n / 256)); n=$((n % 256))
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printf '\%o' $(($n ));
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}
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# Print the big-endian 4-byte binary representation of $1
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uint32_binary () {
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printf "$(uint32_octal "$1")"
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}
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# Print a pack header, version 2, for a pack with $1 objects
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pack_header () {
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printf 'PACK' &&
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printf '\0\0\0\2' &&
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uint32_binary "$1"
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}
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# Print the pack data for object $1, as a delta against object $2 (or as a full
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# object if $2 is missing or empty). The output is suitable for including
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# directly in the packfile, and represents the entirety of the object entry.
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# Doing this on the fly (especially picking your deltas) is quite tricky, so we
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# have hardcoded some well-known objects. See the case statements below for the
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# complete list.
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pack_obj () {
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case "$1" in
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# empty blob
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e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
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case "$2" in
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'')
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printf '\060\170\234\003\0\0\0\0\1'
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return
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;;
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esac
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;;
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# blob containing "\7\76"
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e68fe8129b546b101aee9510c5328e7f21ca1d18)
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case "$2" in
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'')
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printf '\062\170\234\143\267\3\0\0\116\0\106'
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return
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;;
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01d7713666f4de822776c7622c10f1b07de280dc)
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printf '\165\1\327\161\66\146\364\336\202\47\166' &&
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printf '\307\142\54\20\361\260\175\342\200\334\170' &&
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printf '\234\143\142\142\142\267\003\0\0\151\0\114'
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return
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;;
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esac
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;;
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# blob containing "\7\0"
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01d7713666f4de822776c7622c10f1b07de280dc)
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case "$2" in
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'')
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printf '\062\170\234\143\147\0\0\0\20\0\10'
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return
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;;
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e68fe8129b546b101aee9510c5328e7f21ca1d18)
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printf '\165\346\217\350\22\233\124\153\20\32\356' &&
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printf '\225\20\305\62\216\177\41\312\35\30\170\234' &&
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printf '\143\142\142\142\147\0\0\0\53\0\16'
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return
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;;
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esac
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;;
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esac
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echo >&2 "BUG: don't know how to print $1${2:+ (from $2)}"
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return 1
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}
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# Compute and append pack trailer to "$1"
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pack_trailer () {
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test-sha1 -b <"$1" >trailer.tmp &&
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cat trailer.tmp >>"$1" &&
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rm -f trailer.tmp
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}
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# Remove any existing packs to make sure that
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# whatever we index next will be the pack that we
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# actually use.
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clear_packs () {
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rm -f .git/objects/pack/*
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}
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