1 files changed, 92 insertions, 0 deletions
diff --git a/crypto/openssl/providers/implementations/encode_decode/ml_common_codecs.c b/crypto/openssl/providers/implementations/encode_decode/ml_common_codecs.c
new file mode 100644
index 000000000000..773550c9fb93
--- /dev/null
+++ b/crypto/openssl/providers/implementations/encode_decode/ml_common_codecs.c
@@ -0,0 +1,92 @@
+/*
+ * Copyright 2025 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <string.h>
+#include <openssl/crypto.h>
+#include <openssl/err.h>
+#include <openssl/proverr.h>
+#include "ml_common_codecs.h"
+
+static int pref_cmp(const void *va, const void *vb)
+{
+    const ML_COMMON_PKCS8_FMT_PREF *a = va;
+    const ML_COMMON_PKCS8_FMT_PREF *b = vb;
+
+    /*
+     * Zeros sort last, otherwise the sort is in increasing order.
+     *
+     * The preferences are small enough to ensure the comparison is transitive
+     * as required by qsort(3).  When overflow or underflow is possible, the
+     * correct transitive comparison would be: (b < a) - (a < b).
+     */
+    if (a->pref > 0 && b->pref > 0)
+        return a->pref - b->pref;
+    /* A preference of 0 is "larger" than (sorts after) any nonzero value. */
+    return b->pref - a->pref;
+}
+
+ML_COMMON_PKCS8_FMT_PREF *
+ossl_ml_common_pkcs8_fmt_order(const char *algorithm_name,
+                               const ML_COMMON_PKCS8_FMT *p8fmt,
+                               const char *direction, const char *formats)
+{
+    ML_COMMON_PKCS8_FMT_PREF *ret;
+    int i, count = 0;
+    const char *fmt = formats, *end;
+    const char *sep = "\t ,";
+
+    /* Reserve an extra terminal slot with fmt == NULL */
+    if ((ret = OPENSSL_zalloc((NUM_PKCS8_FORMATS + 1) * sizeof(*ret))) == NULL)
+        return NULL;
+
+    /* Entries that match a format will get a non-zero preference. */
+    for (i = 0; i < NUM_PKCS8_FORMATS; ++i) {
+        ret[i].fmt = &p8fmt[i];
+        ret[i].pref = 0;
+    }
+
+    /* Default to compile-time table order when none specified. */
+    if (formats == NULL)
+        return ret;
+
+    /*
+     * Formats are case-insensitive, separated by spaces, tabs or commas.
+     * Duplicate formats are allowed, the first occurence determines the order.
+     */
+    do {
+        if (*(fmt += strspn(fmt, sep)) == '\0')
+            break;
+        end = fmt + strcspn(fmt, sep);
+        for (i = 0; i < NUM_PKCS8_FORMATS; ++i) {
+            /* Skip slots already selected or with a different name. */
+            if (ret[i].pref > 0
+                || OPENSSL_strncasecmp(ret[i].fmt->p8_name,
+                                       fmt, (end - fmt)) != 0)
+                continue;
+            /* First time match */
+            ret[i].pref = ++count;
+            break;
+        }
+        fmt = end;
+    } while (count < NUM_PKCS8_FORMATS);
+
+    /* No formats matched, raise an error */
+    if (count == 0) {
+        OPENSSL_free(ret);
+        ERR_raise_data(ERR_LIB_PROV, PROV_R_ML_DSA_NO_FORMAT,
+                       "no %s private key %s formats are enabled",
+                       algorithm_name, direction);
+        return NULL;
+    }
+    /* Sort by preference, with 0's last */
+    qsort(ret, NUM_PKCS8_FORMATS, sizeof(*ret), pref_cmp);
+    /* Terminate the list at first unselected entry, perhaps reserved slot. */
+    ret[count].fmt = NULL;
+    return ret;
+}