[PATCH 3/6] qemu: Validate firmware blob configuration

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

There are recommendations and limitations to the name of the
config blobs we need to follow [1].

Firstly, we don't want users to change any value only add new
blobs. This means, that the name must have "opt/" prefix and at
the same time must not begin with "opt/ovmf" nor "opt/org.qemu"
as these are reserved for OVMF or QEMU respectively.

Secondly, there is a limit (FW_CFG_MAX_FILE_PATH in qemu.git) of
56 characters for filename.

1: docs/specs/fw_cfg.txt from qemu.git

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 src/qemu/qemu_validate.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index 584d1375b8..1274159b39 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -762,6 +762,41 @@ qemuValidateDefGetVcpuHotplugGranularity(const virDomainDef *def)
 }
 
 
+#define QEMU_FW_CFG_MAX_FILE_PATH 55
+static int
+qemuValidateDomainDefFWCfg(const virDomainDef *def,
+                           virQEMUCapsPtr qemuCaps G_GNUC_UNUSED)
+{
+    size_t i;
+
+    for (i = 0; i < def->nfw_cfgs; i++) {
+        const virDomainFWCfgDef *f = &def->fw_cfgs[i];
+
+        if (!STRPREFIX(f->name, "opt/")) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Invalid firmware name"));
+            return -1;
+        }
+
+        if (STRPREFIX(f->name, "opt/ovmf/") ||
+            STRPREFIX(f->name, "opt/org.qemu/")) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("That firmware name is reserved"));
+            return -1;
+        }
+
+        if (f->file &&
+            strlen(f->file) > QEMU_FW_CFG_MAX_FILE_PATH) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("firmware file too long"));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+
 int
 qemuValidateDomainDef(const virDomainDef *def,
                       void *opaque)
@@ -978,6 +1013,9 @@ qemuValidateDomainDef(const virDomainDef *def,
         }
     }
 
+    if (qemuValidateDomainDefFWCfg(def, qemuCaps) < 0)
+        return -1;
+
     return 0;
 }
 
-- 
2.26.2