1 files changed, 467 insertions, 0 deletions
diff --git a/src/uri_normalizer.c b/src/uri_normalizer.c
new file mode 100644
index 0000000..bc793f2
--- /dev/null
+++ b/src/uri_normalizer.c
@@ -0,0 +1,467 @@
+/*
+ * HTTP request URI normalization.
+ *
+ * Copyright 2021 Tim Duesterhus <tim@bastelstu.be>
+ *
+ * This program 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
+ * 2 of the License, or (at your option) any later version.
+ *
+ */
+
+#include <import/ist.h>
+
+#include <haproxy/api.h>
+#include <haproxy/buf.h>
+#include <haproxy/chunk.h>
+#include <haproxy/tools.h>
+#include <haproxy/uri_normalizer.h>
+
+/* Encodes '#' as '%23'. */
+enum uri_normalizer_err uri_normalizer_fragment_encode(const struct ist input, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	struct ist output = *dst;
+
+	struct ist scanner = input;
+
+	while (istlen(scanner)) {
+		const struct ist before_hash = istsplit(&scanner, '#');
+
+		if (istcat(&output, before_hash, size) < 0) {
+			err = URI_NORMALIZER_ERR_ALLOC;
+			goto fail;
+		}
+
+		if (istend(before_hash) != istend(scanner)) {
+			if (istcat(&output, ist("%23"), size) < 0) {
+				err = URI_NORMALIZER_ERR_ALLOC;
+				goto fail;
+			}
+		}
+	}
+
+	*dst = output;
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/* Returns 1 if the given character is part of the 'unreserved' set in the
+ * RFC 3986 ABNF.
+ * Returns 0 if not.
+ */
+static int is_unreserved_character(unsigned char c)
+{
+	switch (c) {
+	case 'A'...'Z': /* ALPHA */
+	case 'a'...'z': /* ALPHA */
+	case '0'...'9': /* DIGIT */
+	case '-':
+	case '.':
+	case '_':
+	case '~':
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+/* Decodes percent encoded characters that are part of the 'unreserved' set.
+ *
+ * RFC 3986, section 2.3:
+ * >  URIs that differ in the replacement of an unreserved character with
+ * >  its corresponding percent-encoded US-ASCII octet are equivalent [...]
+ * >  when found in a URI, should be decoded to their corresponding unreserved
+ * >  characters by URI normalizers.
+ *
+ * If `strict` is set to 0 then percent characters that are not followed by a
+ * hexadecimal digit are returned as-is without performing any decoding.
+ * If `strict` is set to 1 then `URI_NORMALIZER_ERR_INVALID_INPUT` is returned
+ * for invalid sequences.
+ */
+enum uri_normalizer_err uri_normalizer_percent_decode_unreserved(const struct ist input, int strict, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	struct ist output = *dst;
+
+	struct ist scanner = input;
+
+	/* The output will either be shortened or have the same length. */
+	if (size < istlen(input)) {
+		err = URI_NORMALIZER_ERR_ALLOC;
+		goto fail;
+	}
+
+	while (istlen(scanner)) {
+		const char current = istshift(&scanner);
+
+		if (current == '%') {
+			if (istlen(scanner) >= 2) {
+				if (ishex(istptr(scanner)[0]) && ishex(istptr(scanner)[1])) {
+					char hex1, hex2, c;
+
+					hex1 = istshift(&scanner);
+					hex2 = istshift(&scanner);
+					c = (hex2i(hex1) << 4) + hex2i(hex2);
+
+					if (is_unreserved_character(c)) {
+						output = __istappend(output, c);
+					}
+					else {
+						output = __istappend(output, current);
+						output = __istappend(output, hex1);
+						output = __istappend(output, hex2);
+					}
+
+					continue;
+				}
+			}
+
+			if (strict) {
+				err = URI_NORMALIZER_ERR_INVALID_INPUT;
+				goto fail;
+			}
+			else {
+				output = __istappend(output, current);
+			}
+		}
+		else {
+			output = __istappend(output, current);
+		}
+	}
+
+	*dst = output;
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/* Uppercases letters used in percent encoding.
+ *
+ * If `strict` is set to 0 then percent characters that are not followed by a
+ * hexadecimal digit are returned as-is without modifying the following letters.
+ * If `strict` is set to 1 then `URI_NORMALIZER_ERR_INVALID_INPUT` is returned
+ * for invalid sequences.
+ */
+enum uri_normalizer_err uri_normalizer_percent_upper(const struct ist input, int strict, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	struct ist output = *dst;
+
+	struct ist scanner = input;
+
+	/* The output will have the same length. */
+	if (size < istlen(input)) {
+		err = URI_NORMALIZER_ERR_ALLOC;
+		goto fail;
+	}
+
+	while (istlen(scanner)) {
+		const char current = istshift(&scanner);
+
+		if (current == '%') {
+			if (istlen(scanner) >= 2) {
+				if (ishex(istptr(scanner)[0]) && ishex(istptr(scanner)[1])) {
+					output = __istappend(output, current);
+					output = __istappend(output, toupper(istshift(&scanner)));
+					output = __istappend(output, toupper(istshift(&scanner)));
+					continue;
+				}
+			}
+
+			if (strict) {
+				err = URI_NORMALIZER_ERR_INVALID_INPUT;
+				goto fail;
+			}
+			else {
+				output = __istappend(output, current);
+			}
+		}
+		else {
+			output = __istappend(output, current);
+		}
+	}
+
+	*dst = output;
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/* Removes `/./` from the given path. */
+enum uri_normalizer_err uri_normalizer_path_dot(const struct ist path, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	struct ist newpath = *dst;
+
+	struct ist scanner = path;
+
+	/* The path will either be shortened or have the same length. */
+	if (size < istlen(path)) {
+		err = URI_NORMALIZER_ERR_ALLOC;
+		goto fail;
+	}
+
+	while (istlen(scanner) > 0) {
+		const struct ist segment = istsplit(&scanner, '/');
+
+		if (!isteq(segment, ist("."))) {
+			if (istcat(&newpath, segment, size) < 0) {
+				/* This is impossible, because we checked the size of the destination buffer. */
+				my_unreachable();
+				err = URI_NORMALIZER_ERR_INTERNAL_ERROR;
+				goto fail;
+			}
+
+			if (istend(segment) != istend(scanner))
+				newpath = __istappend(newpath, '/');
+		}
+	}
+
+	*dst = newpath;
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/* Merges `/../` with preceding path segments.
+ *
+ * If `full` is set to `0` then `/../` will be printed at the start of the resulting
+ * path if the number of `/../` exceeds the number of other segments. If `full` is
+ * set to `1` these will not be printed.
+ */
+enum uri_normalizer_err uri_normalizer_path_dotdot(const struct ist path, int full, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	char * const tail = istptr(*dst) + size;
+	char *head = tail;
+
+	ssize_t offset = istlen(path) - 1;
+
+	int up = 0;
+
+	/* The path will either be shortened or have the same length. */
+	if (size < istlen(path)) {
+		err = URI_NORMALIZER_ERR_ALLOC;
+		goto fail;
+	}
+
+	/* Handle `/..` at the end of the path without a trailing slash. */
+	if (offset >= 2 && istmatch(istadv(path, offset - 2), ist("/.."))) {
+		up++;
+		offset -= 2;
+	}
+
+	while (offset >= 0) {
+		if (offset >= 3 && istmatch(istadv(path, offset - 3), ist("/../"))) {
+			up++;
+			offset -= 3;
+			continue;
+		}
+
+		if (up > 0) {
+			/* Skip the slash. */
+			offset--;
+
+			/* First check whether we already reached the start of the path,
+			 * before popping the current `/../`.
+			 */
+			if (offset >= 0) {
+				up--;
+
+				/* Skip the current path segment. */
+				while (offset >= 0 && istptr(path)[offset] != '/')
+					offset--;
+			}
+		}
+		else {
+			/* Prepend the slash. */
+			*(--head) = istptr(path)[offset];
+			offset--;
+
+			/* Prepend the current path segment. */
+			while (offset >= 0 && istptr(path)[offset] != '/') {
+				*(--head) = istptr(path)[offset];
+				offset--;
+			}
+		}
+	}
+
+	if (up > 0) {
+		/* Prepend a trailing slash. */
+		*(--head) = '/';
+
+		if (!full) {
+			/* Prepend unconsumed `/..`. */
+			do {
+				*(--head) = '.';
+				*(--head) = '.';
+				*(--head) = '/';
+				up--;
+			} while (up > 0);
+		}
+	}
+
+	*dst = ist2(head, tail - head);
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/* Merges adjacent slashes in the given path. */
+enum uri_normalizer_err uri_normalizer_path_merge_slashes(const struct ist path, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	struct ist newpath = *dst;
+
+	struct ist scanner = path;
+
+	/* The path will either be shortened or have the same length. */
+	if (size < istlen(path)) {
+		err = URI_NORMALIZER_ERR_ALLOC;
+		goto fail;
+	}
+
+	while (istlen(scanner) > 0) {
+		const char current = istshift(&scanner);
+
+		if (current == '/') {
+			while (istlen(scanner) > 0 && *istptr(scanner) == '/')
+				scanner = istnext(scanner);
+		}
+
+		newpath = __istappend(newpath, current);
+	}
+
+	*dst = newpath;
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/* Compares two query parameters by name. Query parameters are ordered
+ * as with memcmp. Shorter parameter names are ordered lower. Identical
+ * parameter names are compared by their pointer to maintain a stable
+ * sort.
+ */
+static int query_param_cmp(const void *a, const void *b)
+{
+	const struct ist param_a = *(struct ist*)a;
+	const struct ist param_b = *(struct ist*)b;
+	const struct ist param_a_name = iststop(param_a, '=');
+	const struct ist param_b_name = iststop(param_b, '=');
+
+	int cmp = istdiff(param_a_name, param_b_name);
+
+	if (cmp != 0)
+		return cmp;
+
+	/* The contents are identical: Compare the pointer. */
+	if (istptr(param_a) < istptr(param_b))
+		return -1;
+
+	if (istptr(param_a) > istptr(param_b))
+		return 1;
+
+	return 0;
+}
+
+/* Sorts the parameters within the given query string. */
+enum uri_normalizer_err uri_normalizer_query_sort(const struct ist query, const char delim, struct ist *dst)
+{
+	enum uri_normalizer_err err;
+
+	const size_t size = istclear(dst);
+	struct ist newquery = *dst;
+
+	struct ist scanner = query;
+
+	const struct buffer *trash = get_trash_chunk();
+	struct ist *params = (struct ist *)b_orig(trash);
+	const size_t max_param = b_size(trash) / sizeof(*params);
+	size_t param_count = 0;
+
+	size_t i;
+
+	/* The query will have the same length. */
+	if (size < istlen(query)) {
+		err = URI_NORMALIZER_ERR_ALLOC;
+		goto fail;
+	}
+
+	/* Handle the leading '?'. */
+	newquery = __istappend(newquery, istshift(&scanner));
+
+	while (istlen(scanner) > 0) {
+		const struct ist param = istsplit(&scanner, delim);
+
+		if (param_count + 1 > max_param) {
+			err = URI_NORMALIZER_ERR_ALLOC;
+			goto fail;
+		}
+
+		params[param_count] = param;
+		param_count++;
+	}
+
+	qsort(params, param_count, sizeof(*params), query_param_cmp);
+
+	for (i = 0; i < param_count; i++) {
+		if (i > 0)
+			newquery = __istappend(newquery, delim);
+
+		if (istcat(&newquery, params[i], size) < 0) {
+			/* This is impossible, because we checked the size of the destination buffer. */
+			my_unreachable();
+			err = URI_NORMALIZER_ERR_INTERNAL_ERROR;
+			goto fail;
+		}
+	}
+
+	*dst = newquery;
+
+	return URI_NORMALIZER_ERR_NONE;
+
+  fail:
+
+	return err;
+}
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */