[libvirt PATCH v4 07/12] tools: support automatically constructing SEV-ES vCPU state

The VMSA files contain the expected CPU register state for the VM. Their content varies based on a few pieces of the stack - AMD CPU architectural initial state - KVM hypervisor VM CPU initialization - QEMU userspace VM CPU initialization - AMD CPU SKU (family/model/stepping) The first three pieces of information we can obtain through code inspection. The last piece of information we can take on the command line. This allows a user to validate a SEV-ES guest merely by providing the CPU SKU information, using --cpu-family, --cpu-model, --cpu-stepping. This avoids the need to obtain or construct VMSA files directly. Reviewed-by: Ján Tomko <jtomko(a)redhat.com&gt; Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- docs/manpages/virt-qemu-sev-validate.rst | 45 +++ tools/virt-qemu-sev-validate | 467 +++++++++++++++++++++++ 2 files changed, 512 insertions(+) diff --git a/docs/manpages/virt-qemu-sev-validate.rst b/docs/manpages/virt-qemu-sev-validate.rst index d51969d0b2..34ef328fe8 100644 --- a/docs/manpages/virt-qemu-sev-validate.rst +++ b/docs/manpages/virt-qemu-sev-validate.rst @@ -245,6 +245,24 @@ Validate the measurement of a SEV-ES SMP guest booting from disk: --build-id 13 \ --policy 7 +Validate the measurement of a SEV-ES SMP guest booting from disk, with +automatically constructed VMSA: + +:: + + # virt-dom-sev-validate \ + --firmware OVMF.sev.fd \ + --num-cpus 2 \ + --cpu-family 23 \ + --cpu-model 49 \ + --cpu-stepping 0 \ + --tk this-guest-tk.bin \ + --measurement Zs2pf19ubFSafpZ2WKkwquXvACx9Wt/BV+eJwQ/taO8jhyIj/F8swFrybR1fZ2ID \ + --api-major 0 \ + --api-minor 24 \ + --build-id 13 \ + --policy 7 + Fetch from remote libvirt ------------------------- @@ -291,6 +309,20 @@ Validate the measurement of a SEV-ES SMP guest booting from disk: --tk this-guest-tk.bin \ --domain fedora34x86_64 +Validate the measurement of a SEV-ES SMP guest booting from disk, with +automatically constructed VMSA: + +:: + + # virt-dom-sev-validate \ + --connect qemu+ssh://root@some.remote.host/system \ + --firmware OVMF.sev.fd \ + --cpu-family 23 \ + --cpu-model 49 \ + --cpu-stepping 0 \ + --tk this-guest-tk.bin \ + --domain fedora34x86_64 + Fetch from local libvirt ------------------------ @@ -332,6 +364,19 @@ Validate the measurement of a SEV-ES SMP guest booting from disk: --tk this-guest-tk.bin \ --domain fedora34x86_64 +Validate the measurement of a SEV-ES SMP guest booting from disk, with +automatically constructed VMSA: + +:: + + # virt-dom-sev-validate \ + --insecure \ + --cpu-family 23 \ + --cpu-model 49 \ + --cpu-stepping 0 \ + --tk this-guest-tk.bin \ + --domain fedora34x86_64 + EXIT STATUS =========== diff --git a/tools/virt-qemu-sev-validate b/tools/virt-qemu-sev-validate index 6003ba2929..ef8fa6fa27 100755 --- a/tools/virt-qemu-sev-validate +++ b/tools/virt-qemu-sev-validate @@ -42,6 +42,7 @@ import hmac import logging import re import socket +from struct import pack import sys import traceback from uuid import UUID @@ -72,6 +73,427 @@ class InvalidStateException(Exception): pass +class Field(object): + U8 = 0 + U16 = 2 + U32 = 4 + U64 = 8 + + SCALAR = 0 + BITMASK = 1 + ARRAY = 2 + + def __init__(self, name, size, fmt, value, order): + self.name = name + self.size = size + self.value = value + self.fmt = fmt + self.order = order + + +class Struct(object): + def __init__(self, size): + self._fields = {} + self.size = size + + def register_field(self, name, size, fmt=Field.SCALAR, defvalue=0): + self._fields[name] = Field(name, size, fmt, + defvalue, len(self.fields)) + + @property + def fields(self): + return sorted(self._fields.values(), key=lambda f: f.order) + + def __getattr__(self, name): + return self._fields[name] + + def __setattr__(self, name, value): + if name in ["_fields", "size"]: + super().__setattr__(name, value) + else: + self._fields[name].value = value + + def binary_format(self): + fmt = ["<"] + datalen = 0 + for field in self.fields: + if field.size == Field.U8: + if field.fmt == Field.ARRAY: + datalen += len(field.value) + fmt += ["%dB" % len(field.value)] + else: + datalen += 1 + fmt += ["B"] + elif field.size == Field.U16: + datalen += 2 + fmt += ["H"] + elif field.size == Field.U32: + datalen += 4 + fmt += ["L"] + elif field.size == Field.U64: + datalen += 8 + fmt += ["Q"] + + pad = self.size - datalen + assert self.size >= 1 + fmt += ["%dB" % pad] + + return "".join(fmt), pad + + def pack(self): + fmt, pad = self.binary_format() + + values = [] + for field in self.fields: + if field.size == Field.U8 and field.fmt == Field.ARRAY: + for _, k in enumerate(field.value): + values.append(k) + else: + values.append(field.value) + values.extend([0] * pad) + + return pack(fmt, *values) + + +class VMSA(Struct): + ATTR_G_SHIFT = 23 + ATTR_G_MASK = (1 << ATTR_G_SHIFT) + ATTR_B_SHIFT = 22 + ATTR_B_MASK = (1 << ATTR_B_SHIFT) + ATTR_L_SHIFT = 21 + ATTR_L_MASK = (1 << ATTR_L_SHIFT) + ATTR_AVL_SHIFT = 20 + ATTR_AVL_MASK = (1 << ATTR_AVL_SHIFT) + ATTR_P_SHIFT = 15 + ATTR_P_MASK = (1 << ATTR_P_SHIFT) + ATTR_DPL_SHIFT = 13 + ATTR_DPL_MASK = (3 << ATTR_DPL_SHIFT) + ATTR_S_SHIFT = 12 + ATTR_S_MASK = (1 << ATTR_S_SHIFT) + ATTR_TYPE_SHIFT = 8 + ATTR_TYPE_MASK = (15 << ATTR_TYPE_SHIFT) + ATTR_A_MASK = (1 << 8) + + ATTR_CS_MASK = (1 << 11) + ATTR_C_MASK = (1 << 10) + ATTR_R_MASK = (1 << 9) + + ATTR_E_MASK = (1 << 10) + ATTR_W_MASK = (1 << 9) + + def __init__(self): + super().__init__(4096) + + # From Linux arch/x86/include/asm/svm.h, we're unpacking the + # struct vmcb_save_area + + self.register_field("es_selector", Field.U16) + self.register_field("es_attrib", Field.U16, Field.BITMASK) + self.register_field("es_limit", Field.U32) + self.register_field("es_base", Field.U64) + + self.register_field("cs_selector", Field.U16) + self.register_field("cs_attrib", Field.U16, Field.BITMASK) + self.register_field("cs_limit", Field.U32) + self.register_field("cs_base", Field.U64) + + self.register_field("ss_selector", Field.U16) + self.register_field("ss_attrib", Field.U16, Field.BITMASK) + self.register_field("ss_limit", Field.U32) + self.register_field("ss_base", Field.U64) + + self.register_field("ds_selector", Field.U16) + self.register_field("ds_attrib", Field.U16, Field.BITMASK) + self.register_field("ds_limit", Field.U32) + self.register_field("ds_base", Field.U64) + + self.register_field("fs_selector", Field.U16) + self.register_field("fs_attrib", Field.U16, Field.BITMASK) + self.register_field("fs_limit", Field.U32) + self.register_field("fs_base", Field.U64) + + self.register_field("gs_selector", Field.U16) + self.register_field("gs_attrib", Field.U16, Field.BITMASK) + self.register_field("gs_limit", Field.U32) + self.register_field("gs_base", Field.U64) + + self.register_field("gdtr_selector", Field.U16) + self.register_field("gdtr_attrib", Field.U16, Field.BITMASK) + self.register_field("gdtr_limit", Field.U32) + self.register_field("gdtr_base", Field.U64) + + self.register_field("ldtr_selector", Field.U16) + self.register_field("ldtr_attrib", Field.U16, Field.BITMASK) + self.register_field("ldtr_limit", Field.U32) + self.register_field("ldtr_base", Field.U64) + + self.register_field("idtr_selector", Field.U16) + self.register_field("idtr_attrib", Field.U16, Field.BITMASK) + self.register_field("idtr_limit", Field.U32) + self.register_field("idtr_base", Field.U64) + + self.register_field("tr_selector", Field.U16) + self.register_field("tr_attrib", Field.U16, Field.BITMASK) + self.register_field("tr_limit", Field.U32) + self.register_field("tr_base", Field.U64) + + self.register_field("reserved_1", + Field.U8, Field.ARRAY, bytearray([0] * 43)) + + self.register_field("cpl", Field.U8) + + self.register_field("reserved_2", + Field.U8, Field.ARRAY, bytearray([0] * 4)) + + self.register_field("efer", Field.U64) + + self.register_field("reserved_3", + Field.U8, Field.ARRAY, bytearray([0] * 104)) + + self.register_field("xss", Field.U64) + self.register_field("cr4", Field.U64) + self.register_field("cr3", Field.U64) + self.register_field("cr0", Field.U64) + self.register_field("dr7", Field.U64) + self.register_field("dr6", Field.U64) + self.register_field("rflags", Field.U64) + self.register_field("rip", Field.U64) + + self.register_field("reserved_4", + Field.U8, Field.ARRAY, bytearray([0] * 88)) + + self.register_field("rsp", Field.U64) + + self.register_field("reserved_5", + Field.U8, Field.ARRAY, bytearray([0] * 24)) + + self.register_field("rax", Field.U64) + self.register_field("star", Field.U64) + self.register_field("lstar", Field.U64) + self.register_field("cstar", Field.U64) + self.register_field("sfmask", Field.U64) + self.register_field("kernel_gs_base", Field.U64) + self.register_field("sysenter_cs", Field.U64) + self.register_field("sysenter_esp", Field.U64) + self.register_field("sysenter_eip", Field.U64) + self.register_field("cr2", Field.U64) + + self.register_field("reserved_6", + Field.U8, Field.ARRAY, bytearray([0] * 32)) + + self.register_field("g_pat", Field.U64) + self.register_field("dbgctl", Field.U64) + self.register_field("br_from", Field.U64) + self.register_field("br_to", Field.U64) + self.register_field("last_excp_from", Field.U64) + self.register_field("last_excp_to", Field.U64) + + self.register_field("reserved_7", + Field.U8, Field.ARRAY, bytearray([0] * 72)) + + self.register_field("spec_ctrl", Field.U32) + + self.register_field("reserved_7b", + Field.U8, Field.ARRAY, bytearray([0] * 4)) + + self.register_field("pkru", Field.U32) + + self.register_field("reserved_7a", + Field.U8, Field.ARRAY, bytearray([0] * 20)) + + self.register_field("reserved_8", Field.U64) # rax duplicate + + self.register_field("rcx", Field.U64) + self.register_field("rdx", Field.U64, Field.BITMASK) + self.register_field("rbx", Field.U64) + + self.register_field("reserved_9", Field.U64) # rsp duplicate + + self.register_field("rbp", Field.U64) + self.register_field("rsi", Field.U64) + self.register_field("rdi", Field.U64) + self.register_field("r8", Field.U64) + self.register_field("r9", Field.U64) + self.register_field("r10", Field.U64) + self.register_field("r11", Field.U64) + self.register_field("r12", Field.U64) + self.register_field("r13", Field.U64) + self.register_field("r14", Field.U64) + self.register_field("r15", Field.U64) + + self.register_field("reserved_10", + Field.U8, Field.ARRAY, bytearray([0] * 16)) + + self.register_field("sw_exit_code", Field.U64) + self.register_field("sw_exit_info_1", Field.U64) + self.register_field("sw_exit_info_2", Field.U64) + self.register_field("sw_scratch", Field.U64) + + self.register_field("reserved_11", + Field.U8, Field.ARRAY, bytearray([0] * 56)) + + self.register_field("xcr0", Field.U64) + self.register_field("valid_bitmap", + Field.U8, Field.ARRAY, bytearray([0] * 16)) + self.register_field("x87_state_gpa", + Field.U64) + + def amd64_cpu_init(self): + # AMD64 Architecture Programmer’s Manual + # Volume 2: System Programming. + # + # 14.1.3 Processor Initialization State + # + # Values after INIT + + self.cr0 = (1 << 4) + self.rip = 0xfff0 + + self.cs_selector = 0xf000 + self.cs_base = 0xffff0000 + self.cs_limit = 0xffff + + self.ds_limit = 0xffff + + self.es_limit = 0xffff + self.fs_limit = 0xffff + self.gs_limit = 0xffff + self.ss_limit = 0xffff + + self.gdtr_limit = 0xffff + self.idtr_limit = 0xffff + + self.ldtr_limit = 0xffff + self.tr_limit = 0xffff + + self.dr6 = 0xffff0ff0 + self.dr7 = 0x0400 + self.rflags = 0x2 + self.xcr0 = 0x1 + + def kvm_cpu_init(self): + # svm_set_cr4() sets guest X86_CR4_MCE bit if host + # has X86_CR4_MCE enabled + self.cr4 = 0x40 + + # svm_set_efer sets guest EFER_SVME (Secure Virtual Machine enable) + self.efer = 0x1000 + + # init_vmcb + init_sys_seg() sets + # SVM_SELECTOR_P_MASK | SEG_TYPE_LDT + self.ldtr_attrib = 0x0082 + + # init_vmcb + init_sys_seg() sets + # SVM_SELECTOR_P_MASK | SEG_TYPE_BUSY_TSS16 + self.tr_attrib = 0x0083 + + # kvm_arch_vcpu_create() in arch/x86/kvm/x86.c + self.g_pat = 0x0007040600070406 + + def qemu_cpu_init(self): + # Based on logic in x86_cpu_reset() + # + # file target/i386/cpu.c + + def attr(mask): + return (mask >> VMSA.ATTR_TYPE_SHIFT) + + self.ldtr_attrib = attr(VMSA.ATTR_P_MASK | + (2 << VMSA.ATTR_TYPE_SHIFT)) + self.tr_attrib = attr(VMSA.ATTR_P_MASK | + (11 << VMSA.ATTR_TYPE_SHIFT)) + self.cs_attrib = attr(VMSA.ATTR_P_MASK | + VMSA.ATTR_S_MASK | + VMSA.ATTR_CS_MASK | + VMSA.ATTR_R_MASK | + VMSA.ATTR_A_MASK) + self.ds_attrib = attr(VMSA.ATTR_P_MASK | + VMSA.ATTR_S_MASK | + VMSA.ATTR_W_MASK | + VMSA.ATTR_A_MASK) + self.es_attrib = attr(VMSA.ATTR_P_MASK | + VMSA.ATTR_S_MASK | + VMSA.ATTR_W_MASK | + VMSA.ATTR_A_MASK) + self.ss_attrib = attr(VMSA.ATTR_P_MASK | + VMSA.ATTR_S_MASK | + VMSA.ATTR_W_MASK | + VMSA.ATTR_A_MASK) + self.fs_attrib = attr(VMSA.ATTR_P_MASK | + VMSA.ATTR_S_MASK | + VMSA.ATTR_W_MASK | + VMSA.ATTR_A_MASK) + self.gs_attrib = attr(VMSA.ATTR_P_MASK | + VMSA.ATTR_S_MASK | + VMSA.ATTR_W_MASK | + VMSA.ATTR_A_MASK) + + self.g_pat = 0x0007040600070406 + + def cpu_sku(self, family, model, stepping): + stepping &= 0xf + model &= 0xff + family &= 0xfff + + self.rdx.value = stepping + + if family > 0xf: + self.rdx.value |= 0xf00 | ((family - 0x0f) << 20) + else: + self.rdx.value |= family << 8 + + self.rdx.value |= ((model & 0xf) << 4) | ((model >> 4) << 16) + + def reset_addr(self, reset_addr): + reset_cs = reset_addr & 0xffff0000 + reset_ip = reset_addr & 0x0000ffff + + self.rip.value = reset_ip + self.cs_base.value = reset_cs + + +class OVMF(object): + + OVMF_TABLE_FOOTER_GUID = UUID("96b582de-1fb2-45f7-baea-a366c55a082d") + SEV_INFO_BLOCK_GUID = UUID("00f771de-1a7e-4fcb-890e-68c77e2fb44e") + + def __init__(self): + self.entries = {} + + def load(self, content): + expect = OVMF.OVMF_TABLE_FOOTER_GUID.bytes_le + actual = content[-48:-32] + if expect != actual: + raise Exception("OVMF footer GUID not found") + + tablelen = int.from_bytes(content[-50:-48], byteorder='little') + + if tablelen == 0: + raise Exception("OVMF tables zero length") + + table = content[-(32 + tablelen):-50] + + self.parse_table(table) + + def parse_table(self, data): + while len(data) > 0: + entryuuid = UUID(bytes_le=data[-16:]) + entrylen = int.from_bytes(data[-18:-16], byteorder='little') + entrydata = data[-entrylen:-18] + + self.entries[str(entryuuid)] = entrydata + + data = data[0:-entrylen] + + def reset_addr(self): + if str(OVMF.SEV_INFO_BLOCK_GUID) not in self.entries: + raise Exception("SEV info block GUID not found") + + reset_addr = int.from_bytes( + self.entries[str(OVMF.SEV_INFO_BLOCK_GUID)], "little") + return reset_addr + + class GUIDTable(abc.ABC): GUID_LEN = 16 @@ -242,6 +664,26 @@ class ConfidentialVM(object): log.debug("VMSA CPU 1(sha256): %s", sha256(self.vmsa_cpu1).hexdigest()) + def build_vmsas(self, family, model, stepping): + ovmf = OVMF() + ovmf.load(self.firmware) + + vmsa = VMSA() + vmsa.amd64_cpu_init() + vmsa.kvm_cpu_init() + vmsa.qemu_cpu_init() + + vmsa.cpu_sku(family, model, stepping) + + self.vmsa_cpu0 = vmsa.pack() + log.debug("VMSA CPU 0(sha256): %s", + sha256(self.vmsa_cpu0).hexdigest()) + + vmsa.reset_addr(ovmf.reset_addr()) + self.vmsa_cpu1 = vmsa.pack() + log.debug("VMSA CPU 1(sha256): %s", + sha256(self.vmsa_cpu1).hexdigest()) + def get_cpu_state(self): if self.num_cpus is None: raise UnsupportedUsageException( @@ -514,6 +956,12 @@ def parse_command_line(): help='VMSA state for the boot CPU') vmconfig.add_argument('--vmsa-cpu1', '-1', help='VMSA state for the additional CPUs') + vmconfig.add_argument('--cpu-family', type=int, + help='Hypervisor host CPU family number') + vmconfig.add_argument('--cpu-model', type=int, + help='Hypervisor host CPU model number') + vmconfig.add_argument('--cpu-stepping', type=int, + help='Hypervisor host CPU stepping number') vmconfig.add_argument('--tik', help='TIK file for domain') vmconfig.add_argument('--tek', @@ -577,6 +1025,20 @@ def check_usage(args): raise UnsupportedUsageException( "--initrd/--cmdline require --kernel") + sku = [args.cpu_family, args.cpu_model, args.cpu_stepping] + if sku.count(None) == len(sku): + if args.vmsa_cpu1 is not None and args.vmsa_cpu0 is None: + raise UnsupportedUsageException( + "VMSA for additional CPU also requires VMSA for boot CPU") + else: + if args.vmsa_cpu0 is not None or args.vmsa_cpu1 is not None: + raise UnsupportedUsageException( + "VMSA files are mutually exclusive with CPU SKU") + + if sku.count(None) != 0: + raise UnsupportedUsageException( + "CPU SKU needs family, model and stepping for SEV-ES domain") + def attest(args): if args.domain is None: @@ -617,6 +1079,11 @@ def attest(args): if args.vmsa_cpu1 is not None: cvm.load_vmsa_cpu1(args.vmsa_cpu1) + if args.cpu_family is not None: + cvm.build_vmsas(args.cpu_family, + args.cpu_model, + args.cpu_stepping) + if args.domain is not None: cvm.load_domain(args.connect, args.domain, -- 2.37.3