185 lines
8.3 KiB
Diff
185 lines
8.3 KiB
Diff
From 74e5313dfa6719f7990c7e175e035d17c9b3f657 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Fri, 5 Jun 2020 23:44:43 +0200
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Subject: Revert "OvmfPkg: use generic QEMU image loader for secure boot
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enabled builds"
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Notes about the RHEL-8.2/20190904-37eef91017ad [edk2-stable201908] ->
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RHEL-8.3/20200603-ca407c7246bf [edk2-stable202005] rebase:
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- new patch (to be dropped later, hopefully)
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This reverts commit ced77332cab626f35fbdb36630be27303d289d79.
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Upstream commit ced77332cab6 ("OvmfPkg: use generic QEMU image loader for
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secure boot enabled builds", 2020-03-05) changes the "Secure Boot threat
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model" in a way that is incompatible with at least two use cases.
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Namely, OVMF has always considered kernel images direct-booted via fw_cfg
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as trusted, bypassing Secure Boot validation. While that approach is
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rooted in a technicality (namely, OVMF doesn't load such images with the
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LoadImage() UEFI boot service / through the UEFI stub, but with the
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Linux/x86 Boot Protocol), that doesn't mean it's wrong. The direct-booted
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kernel from fw_cfg comes from the host side, and Secure Boot in the guest
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is a barrier between the guest firmware and the guest operating system --
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it's not a barrier between host and guest.
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Upstream commit ced77332cab6 points out that the above (historical) OVMF
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behavior differs from ArmVirtQemu's -- the latter direct-boots kernels
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from fw_cfg with the LoadImage() / StartImage() boot services. While that
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difference indeed exists between OVMF and ArmVirtQemu, it's not relevant
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for RHEL downstream. That's because we never build the ArmVirtQemu
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firmware with the Secure Boot feature, so LoadImage() can never reject the
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direct-booted kernel due to a signing issue.
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Subjecting a kernel direct-booted via fw_cfg to Secure Boot verification
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breaks at least two use cases with OVMF:
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- It breaks the %check stage in the SPEC file.
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In that stage, we use the "ovmf-vars-generator" utility from the
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"qemu-ovmf-secureboot" project, for verifying whether the Secure Boot
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operational mode is enabled. The guest kernel is supposed to boot, and
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to print "Secure boot enabled".
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As guest kernel, we pick whatever host kernel is available in the Brew
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build root. The kernel in question may be a publicly released RHEL
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kernel, signed with "Red Hat Secure Boot (signing key 1)", or a
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development build, signed for example with "Red Hat Secure Boot Signing
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3 (beta)". Either way, none of these keys are accepted by the
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certificates that were enrolled by "ovmf-vars-generator" /
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"EnrollDefaultKeys.efi" in the %build stage. Therefore, the %check stage
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fails.
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- It breaks "virt-install --location NETWORK-URL" Linux guest
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installations, if the variable store template used for the new domain
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has the Secure Boot operational mode enabled. "virt-install --location"
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fetches the kernel from the remote OS tree, and passes it to the guest
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firmware via fw_cfg. Therefore the above symptom appears (even for
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publicly released OSes).
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Importantly, if the user downloads the installer ISO of the publicly
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released Fedora / RHEL OS, and exposes the ISO to the guest for example
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as a virtio-scsi CD-ROM, then the installation with "virt-install"
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(without "--location") does succeed. That's because that way, "shim" is
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booted first, from the UEFI-bootable CD-ROM. "Shim" does pass Secure
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Boot verification against the Microsoft certificates, and then it is
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"shim" that accepts the "Red Hat Secure Boot (signing key 1)" signature
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on the guest kernel.
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Some ways to approach this problem (without reverting upstream commit
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ced77332cab6):
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- Equip "ovmf-vars-generator" / "EnrollDefaultKeys.efi" to enroll the
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public half of "Red Hat Secure Boot (signing key 1)" in the %build
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stage. Use a publicly released RHEL kernel in the %check stage.
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Downsides:
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- The Brew build root does not offer any particular released RHEL
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kernel, so either the %check stage would have to download it, or the
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SRPM would have to bundle it. However, Brew build environments do not
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have unfettered network access (rightly so), so the download wouldn't
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work. Furthermore, for bundling with the SRPM, such a kernel image
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could be considered too large.
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- Does not solve the "virt-install --location" issue for other vendors'
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signed kernels.
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- Invoke "ovmf-vars-generator" / "EnrollDefaultKeys.efi" multiple times
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during %build, to create multiple varstore templates. One that would
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accept publicly released RHEL kernels, and another to accept development
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kernels. Don't try to use a particular guest kernel for verification;
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instead, check what kernel Brew offers in the build environment, and use
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the varstore template matching *that* kernel.
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Downsides:
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- It may be considered useless to perform %check with a varstore
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template that is *not* the one that we ship.
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- Does not solve the "virt-install --location" issue for other vendors'
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signed kernels.
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- Sign the RHEL kernels such that the currently enrolled certificates
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accept them.
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Downsides:
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- Not feasible at all; it would require Microsoft to sign our kernels.
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"Shim" exists exactly to eliminate such signing requirements.
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- Modify "virt-install --location NETWORK-URL" such that it download a
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complete (UEFI-bootable) installer ISO image, rather than broken-out
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vmlinuz / initrd files. In other words, replace direct (fw_cfg) kernel
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boot with a CD-ROM / "shim" boot, internally to "virt-install".
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Downsides:
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- Defeats the goal of "virt-install --location NETWORK-URL", and defeats
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the network installation method of (for example) Anaconda.
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For now, revert upstream commit ced77332cab6, in order to return to the
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model we had used in RHEL-8.2 and before. The following ticket has been
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filed to investigate the problem separately:
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<https://bugzilla.redhat.com/show_bug.cgi?id=1844653>.
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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OvmfPkg/OvmfPkgIa32.dsc | 4 ----
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OvmfPkg/OvmfPkgIa32X64.dsc | 4 ----
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OvmfPkg/OvmfPkgX64.dsc | 4 ----
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3 files changed, 12 deletions(-)
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diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
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index e8868136d8..5b1e757cb9 100644
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--- a/OvmfPkg/OvmfPkgIa32.dsc
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+++ b/OvmfPkg/OvmfPkgIa32.dsc
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@@ -379,11 +379,7 @@
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PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
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MpInitLib|UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
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QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
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-!if $(SECURE_BOOT_ENABLE) == TRUE
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- QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
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-!else
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QemuLoadImageLib|OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.inf
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-!endif
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!if $(TPM_ENABLE) == TRUE
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Tpm12DeviceLib|SecurityPkg/Library/Tpm12DeviceLibTcg/Tpm12DeviceLibTcg.inf
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Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibTcg2/Tpm2DeviceLibTcg2.inf
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diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
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index d05275a324..5dffc32105 100644
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--- a/OvmfPkg/OvmfPkgIa32X64.dsc
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+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
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@@ -383,11 +383,7 @@
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PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
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MpInitLib|UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
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QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
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-!if $(SECURE_BOOT_ENABLE) == TRUE
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- QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
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-!else
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QemuLoadImageLib|OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.inf
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-!endif
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!if $(TPM_ENABLE) == TRUE
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Tpm12DeviceLib|SecurityPkg/Library/Tpm12DeviceLibTcg/Tpm12DeviceLibTcg.inf
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Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibTcg2/Tpm2DeviceLibTcg2.inf
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diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
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index cac4cecf18..a2a76fdeea 100644
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--- a/OvmfPkg/OvmfPkgX64.dsc
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+++ b/OvmfPkg/OvmfPkgX64.dsc
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@@ -383,11 +383,7 @@
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PciLib|OvmfPkg/Library/DxePciLibI440FxQ35/DxePciLibI440FxQ35.inf
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MpInitLib|UefiCpuPkg/Library/MpInitLib/DxeMpInitLib.inf
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QemuFwCfgS3Lib|OvmfPkg/Library/QemuFwCfgS3Lib/DxeQemuFwCfgS3LibFwCfg.inf
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-!if $(SECURE_BOOT_ENABLE) == TRUE
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- QemuLoadImageLib|OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
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-!else
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QemuLoadImageLib|OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.inf
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-!endif
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!if $(TPM_ENABLE) == TRUE
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Tpm12DeviceLib|SecurityPkg/Library/Tpm12DeviceLibTcg/Tpm12DeviceLibTcg.inf
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Tpm2DeviceLib|SecurityPkg/Library/Tpm2DeviceLibTcg2/Tpm2DeviceLibTcg2.inf
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--
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2.18.1
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