[PULL 05/37] crypto/x509-utils: Add helper functions for certificate store

[Eric Farman <farman@linux.ibm.com>]

From: Zhuoying Cai <zycai@linux.ibm.com>

Introduce new helper functions for x509 certificate, which will be used
by the certificate store:

qcrypto_x509_convert_cert_der() - converts a certificate from PEM to DER format

These functions provide support for certificate format conversion.

Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260730214624.2328883-4-zycai@linux.ibm.com
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
 crypto/x509-utils.c         | 49 +++++++++++++++++++++++++++++++++++++
 include/crypto/x509-utils.h | 21 ++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/crypto/x509-utils.c b/crypto/x509-utils.c
index 1b497caae8..369e7ca6af 100644
--- a/crypto/x509-utils.c
+++ b/crypto/x509-utils.c
@@ -82,6 +82,46 @@ int qcrypto_get_x509_cert_fingerprint(uint8_t *cert, size_t size,
     return ret;
 }
 
+int qcrypto_x509_convert_cert_der(uint8_t *cert, size_t size,
+                                  uint8_t **result, size_t *resultlen,
+                                  Error **errp)
+{
+    int ret = -1;
+    int rc;
+    gnutls_x509_crt_t crt;
+    gnutls_datum_t datum = {.data = cert, .size = size};
+    gnutls_datum_t datum_der = {.data = NULL, .size = 0};
+
+    rc = gnutls_x509_crt_init(&crt);
+    if (rc < 0) {
+        error_setg(errp, "Failed to initialize certificate: %s", gnutls_strerror(rc));
+        return ret;
+    }
+
+    rc = gnutls_x509_crt_import(crt, &datum, GNUTLS_X509_FMT_PEM);
+    if (rc != 0) {
+        error_setg(errp, "Failed to import certificate: %s", gnutls_strerror(rc));
+        goto cleanup;
+    }
+
+    rc = gnutls_x509_crt_export2(crt, GNUTLS_X509_FMT_DER, &datum_der);
+    if (rc != 0) {
+        error_setg(errp, "Failed to convert certificate to DER format: %s",
+                   gnutls_strerror(rc));
+        goto cleanup;
+    }
+
+    *resultlen = datum_der.size;
+    *result = g_memdup2(datum_der.data, datum_der.size);
+
+    ret = 0;
+
+cleanup:
+    gnutls_x509_crt_deinit(crt);
+    g_free(datum_der.data);
+    return ret;
+}
+
 #else /* ! CONFIG_GNUTLS */
 
 int qcrypto_get_x509_cert_fingerprint(uint8_t *cert, size_t size,
@@ -94,4 +134,13 @@ int qcrypto_get_x509_cert_fingerprint(uint8_t *cert, size_t size,
     return -1;
 }
 
+int qcrypto_x509_convert_cert_der(uint8_t *cert, size_t size,
+                                  uint8_t **result,
+                                  size_t *resultlen,
+                                  Error **errp)
+{
+    error_setg(errp, "GNUTLS is required to export X.509 certificate");
+    return -1;
+}
+
 #endif /* ! CONFIG_GNUTLS */
diff --git a/include/crypto/x509-utils.h b/include/crypto/x509-utils.h
index 1e99661a71..91ae79fb03 100644
--- a/include/crypto/x509-utils.h
+++ b/include/crypto/x509-utils.h
@@ -19,4 +19,25 @@ int qcrypto_get_x509_cert_fingerprint(uint8_t *cert, size_t size,
                                       size_t *resultlen,
                                       Error **errp);
 
+/**
+ * qcrypto_x509_convert_cert_der
+ * @cert: pointer to the raw certificate data in PEM format
+ * @size: size of the certificate
+ * @result: output location for the allocated buffer for the certificate
+ *          in DER format
+ *          (the function allocates memory which must be freed by the caller)
+ * @resultlen: pointer to the size of the buffer (will be updated with the
+ *             actual size of the DER-encoded certificate)
+ * @errp: error pointer
+ *
+ * Convert the given @cert from PEM to DER format.
+ *
+ * Returns: 0 on success,
+ *         -1 on error.
+ */
+int qcrypto_x509_convert_cert_der(uint8_t *cert, size_t size,
+                                  uint8_t **result,
+                                  size_t *resultlen,
+                                  Error **errp);
+
 #endif
-- 
2.55.0