s390x/diag: Implement DIAG 508 subcode 1 for signature verification
DIAG 508 subcode 1 performs signature-verification on signed components. A signed component may be a Linux kernel image, or any other signed binary. **Verification of initrd is not supported.** The instruction call expects two item-pairs: an address of a device component, an address of the analogous signature file (in PKCS#7 DER format), and their respective lengths. All of this data should be encapsulated within a Diag508SigVerifBlock. The DIAG handler will read from the provided addresses to retrieve the necessary data, parse the signature file, then perform the signature-verification. Because there is no way to correlate a specific certificate to a component, each certificate in the store is tried until either verification succeeds, or all certs have been exhausted. A return code of 1 indicates success, and the index and length of the corresponding certificate will be set in the Diag508SigVerifBlock. The following values indicate failure: 0x0102: no certificates are available in the store 0x0202: component data is invalid 0x0302: PKCS#7 format signature is invalid 0x0402: signature-verification failed 0x0502: length of Diag508SigVerifBlock is invalid Signed-off-by: Collin Walling <walling@linux.ibm.com> Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com> Reviewed-by: Thomas Huth <thuth@redhat.com> Reviewed-by: Farhan Ali <alifm@linux.ibm.com> Link: https://lore.kernel.org/qemu-devel/20260730214624.2328883-15-zycai@linux.ibm.com Signed-off-by: Eric Farman <farman@linux.ibm.com>
Collin Walling committed
Jul 30, 2026 at 17:46 UTC
f5faede1ea8f99bd61e4c30c3c473cf104fd2fc4
3 files changed
+160
-1
docs/specs/s390x-secure-ipl.rst
+17
@@ -84,3 +84,20 @@ that requires assistance from QEMU.
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Subcode 0 - query installed subcodes
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Returns a 64-bit mask indicating which subcodes are supported.
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+
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+Subcode 1 - perform signature verification
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+ Perform signature-verification on a signed component, using certificates
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+ from the certificate store and leveraging qcrypto libraries to perform
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+ this operation.
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+
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+ Note: verification of initrd is not supported.
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+
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+ A return code of 1 indicates success, and the index and length of the
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+ corresponding certificate will be set in the Diag508SigVerifBlock.
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+ The following values indicate failure:
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+
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+ * ``0x0102``: no certificates are available in the store
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+ * ``0x0202``: component data is invalid
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+ * ``0x0302``: PKCS#7 format signature is invalid
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+ * ``0x0402``: signature-verification failed
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+ * ``0x0502``: length of Diag508SigVerifBlock is invalid
include/hw/s390x/ipl/diag508.h
+30
@@ -11,5 +11,35 @@
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#define S390X_DIAG508_H
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#define DIAG_508_SUBC_QUERY_SUBC 0x0000
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+#define DIAG_508_SUBC_SIG_VERIF 0x8000
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+
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+#define DIAG_508_RC_OK 0x0001
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+#define DIAG_508_RC_NO_CERTS 0x0102
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+#define DIAG_508_RC_INVAL_COMP_DATA 0x0202
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+#define DIAG_508_RC_INVAL_PKCS7_SIG 0x0302
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+#define DIAG_508_RC_FAIL_VERIF 0x0402
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+#define DIAG_508_RC_INVAL_LEN 0x0502
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+
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+/*
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+ * Maximum component and signature sizes for current secure boot implementation
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+ * Not architecturally defined and may need to revisit if increased
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+ */
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+#define DIAG_508_MAX_COMP_LEN 0x10000000
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+#define DIAG_508_MAX_SIG_LEN 4096
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+
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+struct Diag508SigVerifBlock {
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+ uint32_t length;
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+ uint8_t reserved0[3];
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+ uint8_t version;
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+ uint32_t reserved[2];
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+ uint8_t cert_store_index;
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+ uint8_t reserved1[7];
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+ uint64_t cert_len;
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+ uint64_t comp_len;
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+ uint64_t comp_addr;
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+ uint64_t sig_len;
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+ uint64_t sig_addr;
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+};
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+typedef struct Diag508SigVerifBlock Diag508SigVerifBlock;
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#endif
target/s390x/diag.c
+113
-1
@@ -12,6 +12,7 @@
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* GNU General Public License for more details.
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*/
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+#include <inttypes.h>
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#include "qemu/osdep.h"
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#include "cpu.h"
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#include "s390x-internal.h"
@@ -620,9 +621,112 @@ void handle_diag_320(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
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}
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}
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+static bool diag_508_verify_sig(uint8_t *cert, size_t cert_size,
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+ uint8_t *comp, size_t comp_size,
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+ uint8_t *sig, size_t sig_size)
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+{
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+ g_autofree uint8_t *sig_pem = NULL;
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+ size_t sig_size_pem;
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+ int rc;
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+
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+ /*
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+ * PKCS#7 signature with DER format
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+ * Convert to PEM format for signature verification
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+ *
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+ * Ignore errors during qcrypto signature format conversion and verification
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+ * Return false on any error, treating it as a verification failure
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+ */
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+ rc = qcrypto_pkcs7_convert_sig_pem(sig, sig_size, &sig_pem, &sig_size_pem, NULL);
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+ if (rc < 0) {
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+ return false;
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+ }
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+
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+ rc = qcrypto_x509_verify_sig(cert, cert_size,
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+ comp, comp_size,
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+ sig_pem, sig_size_pem, NULL);
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+ if (rc < 0) {
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+ return false;
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+ }
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+
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+ return true;
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+}
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+
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+static int handle_diag508_sig_verif(CPUS390XState *env, uint64_t addr)
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+{
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+ int verified;
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+ uint32_t svb_len;
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+ uint64_t comp_len, comp_addr;
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+ uint64_t sig_len, sig_addr;
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+ g_autofree uint8_t *comp = NULL;
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+ g_autofree uint8_t *sig = NULL;
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+ g_autofree Diag508SigVerifBlock *svb = NULL;
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+ size_t svb_size = sizeof(Diag508SigVerifBlock);
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+ S390IPLCertificateStore *cs = s390_ipl_get_certificate_store();
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+
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+ if (!cs->count) {
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+ return DIAG_508_RC_NO_CERTS;
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+ }
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+
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+ svb = g_new0(Diag508SigVerifBlock, 1);
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+ s390_ipl_read(env, addr, svb, svb_size);
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+
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+ svb_len = be32_to_cpu(svb->length);
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+ if (svb_len != svb_size) {
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+ return DIAG_508_RC_INVAL_LEN;
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+ }
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+
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+ comp_len = be64_to_cpu(svb->comp_len);
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+ comp_addr = be64_to_cpu(svb->comp_addr);
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+ sig_len = be64_to_cpu(svb->sig_len);
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+ sig_addr = be64_to_cpu(svb->sig_addr);
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+
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+ if (!comp_len || !comp_addr || comp_len > DIAG_508_MAX_COMP_LEN) {
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+ if (comp_len > DIAG_508_MAX_COMP_LEN) {
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+ warn_report("DIAG 0x508: component length %" PRIu64
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+ " exceeds current maximum %u",
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+ comp_len, DIAG_508_MAX_COMP_LEN);
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+ }
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+ return DIAG_508_RC_INVAL_COMP_DATA;
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+ }
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+
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+ if (!sig_len || !sig_addr || sig_len > DIAG_508_MAX_SIG_LEN) {
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+ if (sig_len > DIAG_508_MAX_SIG_LEN) {
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+ warn_report("DIAG 0x508: signature length %" PRIu64
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+ " exceeds current maximum %u",
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+ sig_len, DIAG_508_MAX_SIG_LEN);
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+ }
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+ return DIAG_508_RC_INVAL_PKCS7_SIG;
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+ }
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+
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+ comp = g_malloc0(comp_len);
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+ s390_ipl_read(env, comp_addr, comp, comp_len);
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+
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+ sig = g_malloc0(sig_len);
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+ s390_ipl_read(env, sig_addr, sig, sig_len);
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+
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+ for (int i = 0; i < cs->count; i++) {
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+ verified = diag_508_verify_sig(cs->certs[i].raw,
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+ cs->certs[i].size,
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+ comp, comp_len,
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+ sig, sig_len);
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+ if (verified) {
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+ svb->cert_store_index = i;
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+ svb->cert_len = cpu_to_be64(cs->certs[i].der_size);
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+ s390_ipl_write(env, addr, svb, svb_size);
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+ return DIAG_508_RC_OK;
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+ }
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+ }
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+
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+ return DIAG_508_RC_FAIL_VERIF;
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+}
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+
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+QEMU_BUILD_BUG_MSG(sizeof(Diag508SigVerifBlock) != 64,
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+ "size of Diag508SigVerifBlock is wrong");
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+
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void handle_diag_508(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
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{
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uint64_t subcode = env->regs[r3];
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+ uint64_t addr = env->regs[r1];
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int rc;
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if (env->psw.mask & PSW_MASK_PSTATE) {
@@ -637,7 +741,15 @@ void handle_diag_508(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
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switch (subcode) {
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case DIAG_508_SUBC_QUERY_SUBC:
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- rc = 0;
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+ rc = DIAG_508_SUBC_SIG_VERIF;
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+ break;
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+ case DIAG_508_SUBC_SIG_VERIF:
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+ if (!diag_parm_addr_valid(addr, sizeof(Diag508SigVerifBlock), true)) {
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+ s390_program_interrupt(env, PGM_ADDRESSING, ra);
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+ return;
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+ }
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+
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+ rc = handle_diag508_sig_verif(env, addr);
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break;
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default:
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s390_program_interrupt(env, PGM_SPECIFICATION, ra);