1 files changed, 269 insertions, 0 deletions

diff --git a/src/lib/libcrypto/bytestring/bs_ber.c b/src/lib/libcrypto/bytestring/bs_ber.c
new file mode 100644
index 0000000000..e77c98b223
--- /dev/null
+++ b/src/lib/libcrypto/bytestring/bs_ber.c
@@ -0,0 +1,269 @@
+/*      $OpenBSD: bs_ber.c,v 1.1 2021/11/20 18:10:52 jsing Exp $        */
+/*
+ * Copyright (c) 2014, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <string.h>
+
+#include "bytestring.h"
+
+/*
+ * kMaxDepth is a just a sanity limit. The code should be such that the length
+ * of the input being processes always decreases. None the less, a very large
+ * input could otherwise cause the stack to overflow.
+ */
+static const unsigned int kMaxDepth = 2048;
+
+/* Non-strict version that allows a relaxed DER with indefinite form. */
+static int
+cbs_nonstrict_get_any_asn1_element(CBS *cbs, CBS *out, unsigned int *out_tag,
+    size_t *out_header_len)
+{
+        return cbs_get_any_asn1_element_internal(cbs, out,
+            out_tag, out_header_len, 0);
+}
+
+/*
+ * cbs_find_indefinite walks an ASN.1 structure in |orig_in| and sets
+ * |*indefinite_found| depending on whether an indefinite length element was
+ * found. The value of |orig_in| is not modified.
+ *
+ * Returns one on success (i.e. |*indefinite_found| was set) and zero on error.
+ */
+static int
+cbs_find_indefinite(const CBS *orig_in, char *indefinite_found,
+    unsigned int depth)
+{
+        CBS in;
+
+        if (depth > kMaxDepth)
+                return 0;
+
+        CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
+
+        while (CBS_len(&in) > 0) {
+                CBS contents;
+                unsigned int tag;
+                size_t header_len;
+
+                if (!cbs_nonstrict_get_any_asn1_element(&in, &contents, &tag,
+                    &header_len))
+                        return 0;
+
+                /* Indefinite form not allowed by DER. */
+                if (CBS_len(&contents) == header_len && header_len > 0 &&
+                    CBS_data(&contents)[header_len - 1] == 0x80) {
+                        *indefinite_found = 1;
+                        return 1;
+                }
+                if (tag & CBS_ASN1_CONSTRUCTED) {
+                        if (!CBS_skip(&contents, header_len) ||
+                            !cbs_find_indefinite(&contents, indefinite_found,
+                            depth + 1))
+                                return 0;
+                }
+        }
+
+        *indefinite_found = 0;
+        return 1;
+}
+
+/*
+ * is_primitive_type returns true if |tag| likely a primitive type. Normally
+ * one can just test the "constructed" bit in the tag but, in BER, even
+ * primitive tags can have the constructed bit if they have indefinite
+ * length.
+ */
+static char
+is_primitive_type(unsigned int tag)
+{
+        return (tag & 0xc0) == 0 &&
+            (tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) &&
+            (tag & 0x1f) != (CBS_ASN1_SET & 0x1f);
+}
+
+/*
+ * is_eoc returns true if |header_len| and |contents|, as returned by
+ * |cbs_nonstrict_get_any_asn1_element|, indicate an "end of contents" (EOC)
+ * value.
+ */
+static char
+is_eoc(size_t header_len, CBS *contents)
+{
+        const unsigned char eoc[] = {0x0, 0x0};
+
+        return header_len == 2 && CBS_mem_equal(contents, eoc, 2);
+}
+
+/*
+ * cbs_convert_indefinite reads data with DER encoding (but relaxed to allow
+ * indefinite form) from |in| and writes definite form DER data to |out|. If
+ * |squash_header| is set then the top-level of elements from |in| will not
+ * have their headers written. This is used when concatenating the fragments of
+ * an indefinite length, primitive value. If |looking_for_eoc| is set then any
+ * EOC elements found will cause the function to return after consuming it.
+ * It returns one on success and zero on error.
+ */
+static int
+cbs_convert_indefinite(CBS *in, CBB *out, char squash_header,
+    char looking_for_eoc, unsigned int depth)
+{
+        if (depth > kMaxDepth)
+                return 0;
+
+        while (CBS_len(in) > 0) {
+                CBS contents;
+                unsigned int tag;
+                size_t header_len;
+                CBB *out_contents, out_contents_storage;
+
+                if (!cbs_nonstrict_get_any_asn1_element(in, &contents, &tag,
+                    &header_len))
+                        return 0;
+
+                out_contents = out;
+
+                if (CBS_len(&contents) == header_len) {
+                        if (is_eoc(header_len, &contents))
+                                return looking_for_eoc;
+
+                        if (header_len > 0 &&
+                            CBS_data(&contents)[header_len - 1] == 0x80) {
+                                /*
+                                 * This is an indefinite length element. If
+                                 * it's a SEQUENCE or SET then we just need to
+                                 * write the out the contents as normal, but
+                                 * with a concrete length prefix.
+                                 *
+                                 * If it's a something else then the contents
+                                 * will be a series of DER elements of the same
+                                 * type which need to be concatenated.
+                                 */
+                                const char context_specific = (tag & 0xc0)
+                                    == 0x80;
+                                char squash_child_headers =
+                                    is_primitive_type(tag);
+
+                                /*
+                                 * This is a hack, but it sufficies to handle
+                                 * NSS's output. If we find an indefinite
+                                 * length, context-specific tag with a definite,
+                                 * primtive tag inside it, then we assume that
+                                 * the context-specific tag is implicit and the
+                                 * tags within are fragments of a primitive type
+                                 * that need to be concatenated.
+                                 */
+                                if (context_specific &&
+                                    (tag & CBS_ASN1_CONSTRUCTED)) {
+                                        CBS in_copy, inner_contents;
+                                        unsigned int inner_tag;
+                                        size_t inner_header_len;
+
+                                        CBS_init(&in_copy, CBS_data(in),
+                                            CBS_len(in));
+                                        if (!cbs_nonstrict_get_any_asn1_element(
+                                            &in_copy, &inner_contents,
+                                            &inner_tag, &inner_header_len))
+                                                return 0;
+
+                                        if (CBS_len(&inner_contents) >
+                                            inner_header_len &&
+                                            is_primitive_type(inner_tag))
+                                                squash_child_headers = 1;
+                                }
+
+                                if (!squash_header) {
+                                        unsigned int out_tag = tag;
+
+                                        if (squash_child_headers)
+                                                out_tag &=
+                                                    ~CBS_ASN1_CONSTRUCTED;
+
+                                        if (!CBB_add_asn1(out,
+                                            &out_contents_storage, out_tag))
+                                                return 0;
+
+                                        out_contents = &out_contents_storage;
+                                }
+
+                                if (!cbs_convert_indefinite(in, out_contents,
+                                    squash_child_headers,
+                                    1 /* looking for eoc */, depth + 1))
+                                        return 0;
+
+                                if (out_contents != out && !CBB_flush(out))
+                                        return 0;
+
+                                continue;
+                        }
+                }
+
+                if (!squash_header) {
+                        if (!CBB_add_asn1(out, &out_contents_storage, tag))
+                                return 0;
+
+                        out_contents = &out_contents_storage;
+                }
+
+                if (!CBS_skip(&contents, header_len))
+                        return 0;
+
+                if (tag & CBS_ASN1_CONSTRUCTED) {
+                        if (!cbs_convert_indefinite(&contents, out_contents,
+                            0 /* don't squash header */,
+                            0 /* not looking for eoc */, depth + 1))
+                                return 0;
+                } else {
+                        if (!CBB_add_bytes(out_contents, CBS_data(&contents),
+                            CBS_len(&contents)))
+                                return 0;
+                }
+
+                if (out_contents != out && !CBB_flush(out))
+                        return 0;
+        }
+
+        return looking_for_eoc == 0;
+}
+
+int
+CBS_asn1_indefinite_to_definite(CBS *in, uint8_t **out, size_t *out_len)
+{
+        CBB cbb;
+
+        /*
+         * First, do a quick walk to find any indefinite-length elements. Most
+         * of the time we hope that there aren't any and thus we can quickly
+         * return.
+         */
+        char conversion_needed;
+        if (!cbs_find_indefinite(in, &conversion_needed, 0))
+                return 0;
+
+        if (!conversion_needed) {
+                *out = NULL;
+                *out_len = 0;
+                return 1;
+        }
+
+        if (!CBB_init(&cbb, CBS_len(in)))
+                return 0;
+        if (!cbs_convert_indefinite(in, &cbb, 0, 0, 0)) {
+                CBB_cleanup(&cbb);
+                return 0;
+        }
+
+        return CBB_finish(&cbb, out, out_len);
+}