[PATCH v16 06/20] appended signatures: Parse ASN1 node

[Sudhakar Kuppusamy <sudhakar@linux.ibm.com>]

This code allows us to parse ASN1 node and allocating memory to store it.
It will work for anything where the size libtasn1 returns is right:
 - Integers
 - Octet strings
 - DER encoding of other structures

It will _not_ work for things where libtasn1 size requires adjustment:
 - Strings that require an extra NULL byte at the end
 - Bit strings because libtasn1 returns the length in bits, not bytes.

If the function returns a non-NULL value, the caller must free it.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Avnish Chouhan <avnish@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/commands/appendedsig/appendedsig.h | 44 +++++++++
 grub-core/commands/appendedsig/asn1util.c    | 99 ++++++++++++++++++++
 2 files changed, 143 insertions(+)
 create mode 100644 grub-core/commands/appendedsig/appendedsig.h
 create mode 100644 grub-core/commands/appendedsig/asn1util.c

diff --git a/grub-core/commands/appendedsig/appendedsig.h b/grub-core/commands/appendedsig/appendedsig.h
new file mode 100644
index 000000000..601d6164f
--- /dev/null
+++ b/grub-core/commands/appendedsig/appendedsig.h
@@ -0,0 +1,44 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2020, 2022 Free Software Foundation, Inc.
+ *  Copyright (C) 2020, 2022, 2025 IBM Corporation
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libtasn1.h>
+
+extern asn1_node grub_gnutls_gnutls_asn;
+extern asn1_node grub_gnutls_pkix_asn;
+
+/* Do libtasn1 init. */
+extern int
+grub_asn1_init (void);
+
+/*
+ * Read a value from an ASN1 node, allocating memory to store it. It will work
+ * for anything where the size libtasn1 returns is right:
+ *  - Integers
+ *  - Octet strings
+ *  - DER encoding of other structures
+ *
+ * It will _not_ work for things where libtasn1 size requires adjustment:
+ *  - Strings that require an extra null byte at the end
+ *  - Bit strings because libtasn1 returns the length in bits, not bytes.
+ *
+ * If the function returns a non-NULL value, the caller must free it.
+ */
+extern void *
+grub_asn1_allocate_and_read (asn1_node node, const char *name, const char *friendly_name,
+                             grub_int32_t *content_size);
diff --git a/grub-core/commands/appendedsig/asn1util.c b/grub-core/commands/appendedsig/asn1util.c
new file mode 100644
index 000000000..9dd7898ea
--- /dev/null
+++ b/grub-core/commands/appendedsig/asn1util.c
@@ -0,0 +1,99 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2020, 2022 Free Software Foundation, Inc.
+ *  Copyright (C) 2020, 2022, 2025 IBM Corporation
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libtasn1.h>
+#include <grub/types.h>
+#include <grub/err.h>
+#include <grub/mm.h>
+#include <grub/crypto.h>
+#include <grub/misc.h>
+#include <grub/gcrypt/gcrypt.h>
+
+#include "appendedsig.h"
+
+asn1_node grub_gnutls_gnutls_asn = NULL;
+asn1_node grub_gnutls_pkix_asn = NULL;
+
+extern const asn1_static_node grub_gnutls_asn1_tab[];
+extern const asn1_static_node grub_pkix_asn1_tab[];
+
+/*
+ * Read a value from an ASN1 node, allocating memory to store it. It will work
+ * for anything where the size libtasn1 returns is right:
+ *  - Integers
+ *  - Octet strings
+ *  - DER encoding of other structures
+ *
+ * It will _not_ work for things where libtasn1 size requires adjustment:
+ *  - Strings that require an extra NULL byte at the end
+ *  - Bit strings because libtasn1 returns the length in bits, not bytes.
+ *
+ * If the function returns a non-NULL value, the caller must free it.
+ */
+void *
+grub_asn1_allocate_and_read (asn1_node node, const char *name, const char *friendly_name,
+                             grub_int32_t *content_size)
+{
+  grub_int32_t result;
+  grub_uint8_t *tmpstr = NULL;
+  grub_int32_t tmpstr_size = 0;
+
+  result = asn1_read_value (node, name, NULL, &tmpstr_size);
+  if (result != ASN1_MEM_ERROR)
+    {
+      grub_error (GRUB_ERR_BAD_FILE_TYPE, "reading size of %s did not return expected status: %s",
+                  friendly_name, asn1_strerror (result)) ;
+      return NULL;
+    }
+
+  tmpstr = grub_malloc (tmpstr_size);
+  if (tmpstr == NULL)
+    {
+      grub_error (GRUB_ERR_OUT_OF_MEMORY, "could not allocate memory to store %s",
+                  friendly_name) ;
+      return NULL;
+    }
+
+  result = asn1_read_value (node, name, tmpstr, &tmpstr_size);
+  if (result != ASN1_SUCCESS)
+    {
+      grub_free (tmpstr);
+      grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading %s: %s", friendly_name,
+                  asn1_strerror (result)) ;
+      return NULL;
+    }
+
+  *content_size = tmpstr_size;
+
+  return tmpstr;
+}
+
+int
+grub_asn1_init (void)
+{
+  int res;
+
+  res = asn1_array2tree (grub_gnutls_asn1_tab, &grub_gnutls_gnutls_asn, NULL);
+  if (res != ASN1_SUCCESS)
+    return res;
+
+  res = asn1_array2tree (grub_pkix_asn1_tab, &grub_gnutls_pkix_asn, NULL);
+
+  return res;
+}
-- 
2.50.1 (Apple Git-155)


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