Implement SUCI Profile Scheme A for 5G UE

Extend UICC configuration parsing to provide: routing_indicator,
protection_scheme, home_network_public_key, and home_network_public_key_id.
Use the protection_scheme value to decide what SUCI Profile Scheme to
apply during SUCI generation. Add support for Profile Scheme A which
provides ECIES-based encryption using Curve25519 and X9.63 KDF as outlined
in TS 33.501 Section C.3.4.1 Profile A.

When a configuration file specifies an unsupported Profile Scheme,
the NAS layer triggers a fatal error. This occurs either because
Profile Scheme B is unimplemented or the build uses OpenSSL < 3.0,
which lacks Curve25519 and X9.63 KDF support, ensuring users are
informed of the incompatibility.

common/utils/utils.c

@@ -94,6 +94,51 @@ char *itoa(int i) {
   return strdup(buffer);
 }
 
+/****************************************************************************
+ **                                                                        **
+ ** Name:        digit_string_to_bcd_value()                               **
+ **                                                                        **
+ ** Description: Converts a decimal ASCII coded string into its BCD encoded**
+ **              value.                                                    **
+ **                                                                        **
+ ** Inputs:      bcd_value:    Output buffer                               **
+ **              digit_string: Input digit string                          **
+ **              size:         Size of bcd_value in bytes                  **
+ **                                                                        **
+ ** Outputs:     bcd_value:    Converted BCD value                         **
+ **              Return:       0 on success, -1 on error                   **
+ **                                                                        **
+ ***************************************************************************/
+int digit_string_to_bcd_value(uint8_t *bcd_value, const char *digit_string, int size)
+{
+  int i;
+  uint8_t len = strlen(digit_string);
+
+  /* Accept even (size*2) or odd (size*2 - 1) digit counts */
+  if (len < size * 2 - 1 || len > size * 2) {
+    fprintf(stderr, "the string '%s' should be of length %d or %d\n", digit_string, size * 2 - 1, size * 2);
+    return -1;
+  }
+
+  for (i = 0; i < size; i++) {
+    uint8_t low = digit_string[2 * i] - '0';
+    uint8_t high = (2 * i + 1 < len) ? digit_string[2 * i + 1] - '0' : 0xF;
+
+    if (low > 9 || (high > 9 && high != 0xF))
+      goto error;
+
+    bcd_value[i] = (high << 4) | low;
+  }
+
+  return 0;
+
+error:
+  fprintf(stderr, "the string '%s' is not a valid digit string\n", digit_string);
+  for (i = 0; i < size; i++)
+    bcd_value[i] = 0;
+  return -1;
+}
+
 /**
  * @brief Convert a version string x.y.z into numbers.
  *

common/utils/utils.h

@@ -123,6 +123,8 @@ static inline void *malloc_or_fail(size_t size)
 int hex_char_to_hex_value (char c);
 // Converts an hexadecimal ASCII coded string into its value.**
 int hex_string_to_hex_value (uint8_t *hex_value, const char *hex_string, int size);
+// Converts a decimal ASCII coded string into its BCD encoded value.
+int digit_string_to_bcd_value(uint8_t *bcd_value, const char *digit_string, int size);
 
 /* Map task id to printable name. */
 typedef struct {