Re: [PATCH v2 09/25] s390x/diag: Implement DIAG 508 subcode 1 for signature verification

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, May 08, 2025 at 06:50:25PM -0400, Zhuoying Cai wrote:
> From: Collin Walling <walling@linux.ibm.com>
> 
> 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 format),
> and their respective lengths. All of this data should be encapsulated
> within a Diag508SignatureVerificationBlock, with the CertificateStoreInfo
> fields ignored. 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.
> 
> The subcode value is denoted by setting the second-to-left-most bit of
> a 2-byte field.
> 
> A return code of 1 indicates success, and the index and length of the
> corresponding certificate will be set in the CertificateStoreInfo
> portion of the SigVerifBlock. The following values indicate failure:
> 
> 	0x0202: component data is invalid
> 	0x0302: signature is not in PKCS#7 format
> 	0x0402: signature-verification failed
> 
> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
> ---
>  crypto/x509-utils.c            | 54 +++++++++++++++++++++++
>  include/crypto/x509-utils.h    |  4 ++
>  include/hw/s390x/ipl/diag508.h | 22 +++++++++
>  target/s390x/diag.c            | 81 +++++++++++++++++++++++++++++++++-
>  4 files changed, 160 insertions(+), 1 deletion(-)
> 
> diff --git a/crypto/x509-utils.c b/crypto/x509-utils.c
> index 51bd75d4eb..56d9a42f39 100644
> --- a/crypto/x509-utils.c
> +++ b/crypto/x509-utils.c
> @@ -20,6 +20,7 @@
>  #include <gnutls/gnutls.h>
>  #include <gnutls/crypto.h>
>  #include <gnutls/x509.h>
> +#include <gnutls/pkcs7.h>
>  
>  static const int qcrypto_to_gnutls_hash_alg_map[QCRYPTO_HASH_ALGO__MAX] = {
>      [QCRYPTO_HASH_ALGO_MD5] = GNUTLS_DIG_MD5,
> @@ -373,6 +374,51 @@ cleanup:
>      return ret;
>  }
>  
> +int qcrypto_verify_x509_cert(uint8_t *cert, size_t cert_size,
> +                            uint8_t *comp, size_t comp_size,
> +                            uint8_t *sig, size_t sig_size, Error **errp)
> +{
> +    int rc = -1;
> +    gnutls_x509_crt_t crt;
> +    gnutls_pkcs7_t signature;
> +    gnutls_datum_t cert_datum = {.data = cert, .size = cert_size};
> +    gnutls_datum_t data_datum = {.data = comp, .size = comp_size};
> +    gnutls_datum_t sig_datum = {.data = sig, .size = sig_size};
> +    gnutls_x509_crt_fmt_t fmt;
> +
> +    fmt = qcrypto_get_x509_cert_fmt(cert, cert_size, errp);
> +    if (fmt == -1) {
> +        error_setg(errp, "Certificate is neither in DER or PEM format");
> +        return rc;
> +    }
> +
> +    if (gnutls_x509_crt_init(&crt) < 0) {
> +        error_setg(errp, "Failed to initialize certificate");
> +        return rc;
> +    }
> +
> +    if (gnutls_x509_crt_import(crt, &cert_datum, fmt) != 0) {
> +        error_setg(errp, "Failed to import certificate");
> +        goto cleanup;
> +    }
> +
> +    if (gnutls_pkcs7_init(&signature) < 0) {
> +        error_setg(errp, "Failed to initalize pkcs7 data.");
> +        return rc;
> +    }
> +
> +    if (gnutls_pkcs7_import(signature, &sig_datum , fmt) != 0) {
> +        error_setg(errp, "Failed to import signature");
> +    }
> +
> +    rc = gnutls_pkcs7_verify_direct(signature, crt, 0, &data_datum, 0);
> +
> +cleanup:
> +    gnutls_x509_crt_deinit(crt);
> +    gnutls_pkcs7_deinit(signature);
> +    return rc;
> +}
> +
>  #else /* ! CONFIG_GNUTLS */
>  
>  int qcrypto_check_x509_cert_fmt(uint8_t *cert, size_t size,
> @@ -438,4 +484,12 @@ int qcrypto_get_x509_cert_key_id(uint8_t *cert, size_t size,
>      return -ENOTSUP;
>  }
>  
> +int qcrypto_verify_x509_cert(uint8_t *cert, size_t cert_size,
> +                             uint8_t *comp, size_t comp_size,
> +                             uint8_t *sig, size_t sig_size, Error **errp)
> +{
> +    error_setg(errp, "signature-verification support requires GNUTLS");
> +    return -ENOTSUP;
> +}
> +
>  #endif /* ! CONFIG_GNUTLS */
> diff --git a/include/crypto/x509-utils.h b/include/crypto/x509-utils.h
> index cf43de0b2c..ec90667376 100644
> --- a/include/crypto/x509-utils.h
> +++ b/include/crypto/x509-utils.h
> @@ -35,4 +35,8 @@ int qcrypto_get_x509_cert_key_id(uint8_t *cert, size_t size,
>                                   size_t *resultlen,
>                                   Error **errp);
>  
> +int qcrypto_verify_x509_cert(uint8_t *cert, size_t cert_size,
> +                             uint8_t *comp, size_t comp_size,
> +                             uint8_t *sig, size_t sig_size, Error **errp);
> +

Needs API docs to say what all these different params mean

>  #endif

Please always aim to seperate out code from different subsystems into
separate patches, if technically possible.

> diff --git a/include/hw/s390x/ipl/diag508.h b/include/hw/s390x/ipl/diag508.h
> index 6281ad8299..80a5bb906b 100644
> --- a/include/hw/s390x/ipl/diag508.h
> +++ b/include/hw/s390x/ipl/diag508.h

> diff --git a/target/s390x/diag.c b/target/s390x/diag.c
> index 954c95fe50..2171e3275d 100644
> --- a/target/s390x/diag.c
> +++ b/target/s390x/diag.c
> @@ -494,7 +494,10 @@ void handle_diag_320(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
>  
>  void handle_diag_508(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
>  {
> +    S390IPLCertificateStore *qcs = s390_ipl_get_certificate_store();
> +    size_t csi_size = sizeof(Diag508CertificateStoreInfo);
>      uint64_t subcode = env->regs[r3];
> +    uint64_t addr = env->regs[r1];
>      int rc;
>  
>      if (env->psw.mask & PSW_MASK_PSTATE) {
> @@ -509,7 +512,83 @@ void handle_diag_508(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
>  
>      switch (subcode) {
>      case DIAG_508_SUBC_QUERY_SUBC:
> -        rc = 0;
> +        rc = DIAG_508_SUBC_SIG_VERIF;
> +        break;
> +    case DIAG_508_SUBC_SIG_VERIF:
> +        size_t svb_size = sizeof(Diag508SignatureVerificationBlock);
> +        Diag508SignatureVerificationBlock *svb;
> +        uint64_t comp_len, comp_addr;
> +        uint64_t sig_len, sig_addr;
> +        uint8_t *svb_comp;
> +        uint8_t *svb_sig;
> +        int verified;
> +        Error *err = NULL;
> +        int i;
> +
> +        if (!qcs || !qcs->count) {
> +            rc = DIAG_508_RC_NO_CERTS;
> +            break;
> +        }
> +
> +        if (!diag_parm_addr_valid(addr, svb_size, false) ||
> +            !diag_parm_addr_valid(addr, csi_size, true)) {
> +            s390_program_interrupt(env, PGM_ADDRESSING, ra);
> +            return;
> +        }
> +
> +        svb = g_new0(Diag508SignatureVerificationBlock, 1);
> +        cpu_physical_memory_read(addr, svb, svb_size);
> +
> +        comp_len = be64_to_cpu(svb->comp_len);
> +        comp_addr = be64_to_cpu(svb->comp_addr);
> +        sig_len = be64_to_cpu(svb->sig_len);
> +        sig_addr = be64_to_cpu(svb->sig_addr);
> +
> +        if (!comp_len || !comp_addr) {
> +            rc = DIAG_508_RC_INVAL_COMP_DATA;
> +            g_free(svb);
> +            break;
> +        }
> +
> +        if (!sig_len || !sig_addr) {
> +            rc = DIAG_508_RC_INVAL_PKCS7_SIG;
> +            g_free(svb);
> +            break;
> +        }
> +
> +        svb_comp = g_malloc0(comp_len);
> +        cpu_physical_memory_read(comp_addr, svb_comp, comp_len);
> +
> +        svb_sig = g_malloc0(sig_len);
> +        cpu_physical_memory_read(sig_addr, svb_sig, sig_len);
> +
> +        rc = DIAG_508_RC_FAIL_VERIF;
> +        /*
> +         * It is uncertain which certificate contains
> +         * the analogous key to verify the signed data
> +         */
> +        for (i = 0; i < qcs->count; i++) {
> +            verified = qcrypto_verify_x509_cert((uint8_t *)qcs->certs[i].raw,
> +                                                qcs->certs[i].size,
> +                                                svb_comp, comp_len,
> +                                                svb_sig, sig_len, &err);
> +
> +            /* return early if GNUTLS is not enabled */
> +            if (verified == -ENOTSUP) {
> +                g_free(svb);
> +                break;
> +            }
> +
> +            if (verified == 0) {
> +                svb->csi.idx = i;
> +                svb->csi.len = cpu_to_be64(qcs->certs[i].size);
> +                cpu_physical_memory_write(addr, &svb->csi, be32_to_cpu(csi_size));
> +                rc = DIAG_508_RC_OK;

Leaks 'svb' here

> +                break;
> +           }
> +        }
> +
> +        g_free(svb);

This and all the other paths leak 'svb_comp' and
'svb_sig'.

Declare all three allocated vars with 'g_autofree' and then you don't
need to remember to manually g_free them.

>          break;
>      default:
>          s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> -- 
> 2.49.0
> 
> 

With regards,
Daniel
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