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signatures: Move ISO 9660 signature to policy

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The previous "fix" caused significant performance degradation without
the signature ever having a chance to trigger. Moving it to policy
seems the best compromise, the alternative being outright removing it.
This commit is contained in:
Arne Welzel 2024-02-26 13:32:27 +01:00
parent f96600391a
commit 1a5ce65e3d
6 changed files with 28 additions and 15 deletions
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15
scripts/base/frameworks/files/magic/general.sig
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@ -296,18 +296,3 @@ signature file-windows-minidump {
file-mime "application/x-windows-minidump", 50
file-magic /^MDMP/
}
# ISO 9660 disk image: First 16 sectors (2k) are arbitrary data.
# The following sector is a volume descriptor with magic string "CD001"
# at offset 1: 16 * 2048 + 1 = 32769
signature file-iso9660 {
file-mime "application/x-iso9660-image", 99
file-magic /^.{32769}CD001/
}
# ISO 9660 disk image, magic string match in next volume descriptor.
# 17 * 2048 + 1 = 34817
signature file-iso9660-2 {
file-mime "application/x-iso9660-image", 99
file-magic /^.{34817}CD001/
}

10
scripts/policy/frameworks/signatures/iso-9660.sig Normal file
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@ -0,0 +1,10 @@
# ISO 9660 disk image: First 16 sectors (2k) are arbitrary data.
# The following sector is a volume descriptor with magic string "CD001"
# at offset 1: 16 * 2048 + 1 = 32769.
#
# However, we do not use exact offset matching /^.{32769}CD001/ as this
# results in major performance degradation.
signature file-iso9660 {
file-mime "application/x-iso9660-image", 99
file-magic /.*CD001/
}

8
scripts/policy/frameworks/signatures/iso-9660.zeek Normal file
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@ -0,0 +1,8 @@
##! Load signature for ISO 9660 disk image and increase
##! default_file_bof_buffer_size to make it functional.
@load-sigs ./iso-9660
# CD001 string is in the 17th sector.
@if ( default_file_bof_buffer_size < (16 + 1) * 2048 )
redef default_file_bof_buffer_size = (16 + 1) * 2048;
@endif

1
scripts/test-all-policy.zeek
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@ -72,6 +72,7 @@
@load frameworks/notice/extend-email/hostnames.zeek
@load files/x509/disable-certificate-events-known-certs.zeek
@load frameworks/packet-filter/shunt.zeek
@load frameworks/signatures/iso-9660.zeek
@load frameworks/software/version-changes.zeek
@load frameworks/software/vulnerable.zeek
# @load frameworks/spicy/record-spicy-batch.zeek