--- /dev/null
+
+/*
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+#define NGX_HTTP_PRIORITY_DEFAULT_URGENCY 3
+#define NGX_HTTP_PRIORITY_URGENCY_MIN 0
+#define NGX_HTTP_PRIORITY_URGENCY_MAX 7
+
+
+/* bare item types we distinguish; others are parsed and discarded */
+
+#define NGX_HTTP_PRIORITY_INTEGER 0
+#define NGX_HTTP_PRIORITY_BOOLEAN 1
+#define NGX_HTTP_PRIORITY_OTHER 2
+
+
+/*
+ * Parse limits. RFC 8941 requires parsers to support at least these many
+ * elements and characters; bounding the counts and individual item lengths
+ * keeps parse time proportional to a well-formed field rather than to what a
+ * peer chooses to send.
+ */
+
+#define NGX_HTTP_PRIORITY_MAX_MEMBERS 1024
+#define NGX_HTTP_PRIORITY_MAX_INNER_ITEMS 256
+#define NGX_HTTP_PRIORITY_MAX_PARAMS 256
+#define NGX_HTTP_PRIORITY_MAX_STRING 1024
+#define NGX_HTTP_PRIORITY_MAX_TOKEN 512
+#define NGX_HTTP_PRIORITY_MAX_BINARY 21848 /* 16384 after decoding */
+
+
+static ngx_int_t ngx_http_priority_parse_key(u_char **pos, u_char *end,
+ ngx_str_t *key);
+static ngx_int_t ngx_http_priority_parse_member(u_char **pos, u_char *end,
+ ngx_str_t *key, ngx_int_t *type, ngx_int_t *value);
+static ngx_int_t ngx_http_priority_parse_value(u_char **pos, u_char *end,
+ ngx_int_t *type, ngx_int_t *value);
+static ngx_int_t ngx_http_priority_parse_inner_list(u_char **pos, u_char *end);
+static ngx_int_t ngx_http_priority_parse_bare_item(u_char **pos, u_char *end,
+ ngx_int_t *type, ngx_int_t *value);
+static ngx_int_t ngx_http_priority_parse_params(u_char **pos, u_char *end);
+static ngx_int_t ngx_http_priority_parse_number(u_char **pos, u_char *end,
+ ngx_int_t *type, ngx_int_t *value);
+static ngx_int_t ngx_http_priority_parse_string(u_char **pos, u_char *end);
+static ngx_int_t ngx_http_priority_parse_token(u_char **pos, u_char *end);
+static ngx_int_t ngx_http_priority_parse_binary(u_char **pos, u_char *end);
+
+
+void
+ngx_http_priority_state_init(ngx_http_priority_state_t *ps)
+{
+ ngx_memzero(ps, sizeof(ngx_http_priority_state_t));
+
+ ps->client.urgency = NGX_HTTP_PRIORITY_DEFAULT_URGENCY;
+ ps->server.urgency = NGX_HTTP_PRIORITY_DEFAULT_URGENCY;
+ ps->effective.urgency = NGX_HTTP_PRIORITY_DEFAULT_URGENCY;
+}
+
+
+/*
+ * Parse an RFC 9218 Priority field, a Structured Fields Dictionary
+ * (RFC 8941). The dictionary is parsed strictly: any syntax error fails
+ * the whole field (RFC 8941, Section 4.2), and only then are the RFC 9218
+ * rules applied, ignoring unknown members, out-of-range urgency and members
+ * of an unexpected type. On error the field is treated as absent and p is
+ * left at defaults; callers keep any previously signalled priority.
+ */
+
+ngx_int_t
+ngx_http_priority_parse(ngx_str_t *field, ngx_http_priority_t *p)
+{
+ u_char *last, *end;
+ ngx_str_t key;
+ ngx_int_t type, value;
+ ngx_uint_t members;
+
+ p->urgency = NGX_HTTP_PRIORITY_DEFAULT_URGENCY;
+ p->incremental = 0;
+ p->urgency_set = 0;
+ p->incremental_set = 0;
+
+ if (field == NULL) {
+ return NGX_OK;
+ }
+
+ /* RFC 8941, Section 4.2.2 */
+
+ last = field->data;
+ end = last + field->len;
+ members = 0;
+
+ /* Section 4.2, step 2: discard leading SP */
+
+ while (last < end && *last == ' ') {
+ last++;
+ }
+
+ while (last < end) {
+
+ if (++members > NGX_HTTP_PRIORITY_MAX_MEMBERS) {
+ return NGX_ERROR;
+ }
+
+ if (ngx_http_priority_parse_member(&last, end, &key, &type, &value)
+ != NGX_OK)
+ {
+ return NGX_ERROR;
+ }
+
+ /*
+ * RFC 8941, Section 4.2.2, step 2.4: a duplicate key replaces the
+ * earlier member. RFC 9218, Section 4: unknown members and members
+ * of an unexpected type are ignored. A repeated u or i therefore
+ * resets to the default first, so a later out-of-range or
+ * wrong-typed value leaves the parameter absent rather than keeping
+ * the earlier one.
+ */
+
+ if (key.len == 1 && key.data[0] == 'u') {
+
+ p->urgency = NGX_HTTP_PRIORITY_DEFAULT_URGENCY;
+ p->urgency_set = 0;
+
+ if (type == NGX_HTTP_PRIORITY_INTEGER
+ && value >= NGX_HTTP_PRIORITY_URGENCY_MIN
+ && value <= NGX_HTTP_PRIORITY_URGENCY_MAX)
+ {
+ p->urgency = (unsigned) value;
+ p->urgency_set = 1;
+ }
+
+ } else if (key.len == 1 && key.data[0] == 'i') {
+
+ p->incremental = 0;
+ p->incremental_set = 0;
+
+ if (type == NGX_HTTP_PRIORITY_BOOLEAN) {
+ p->incremental = (unsigned) value;
+ p->incremental_set = 1;
+ }
+ }
+
+ while (last < end && (*last == ' ' || *last == '\t')) {
+ last++;
+ }
+
+ if (last == end) {
+ break;
+ }
+
+ if (*last++ != ',') {
+ return NGX_ERROR;
+ }
+
+ while (last < end && (*last == ' ' || *last == '\t')) {
+ last++;
+ }
+
+ /* trailing comma */
+
+ if (last == end) {
+ return NGX_ERROR;
+ }
+ }
+
+ return NGX_OK;
+}
+
+
+/*
+ * Parse one dictionary member and its parameters (RFC 8941, Section 4.2.2).
+ * A bare key (no "=") is a Boolean true; type/value then describe the
+ * member's value so the caller can pick out u and i and ignore the rest.
+ */
+
+static ngx_int_t
+ngx_http_priority_parse_member(u_char **pos, u_char *end, ngx_str_t *key,
+ ngx_int_t *type, ngx_int_t *value)
+{
+ u_char *last;
+
+ last = *pos;
+
+ if (ngx_http_priority_parse_key(&last, end, key) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ if (last < end && *last == '=') {
+ last++;
+
+ if (ngx_http_priority_parse_value(&last, end, type, value) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ } else {
+ *type = NGX_HTTP_PRIORITY_BOOLEAN;
+ *value = 1;
+
+ if (ngx_http_priority_parse_params(&last, end) != NGX_OK) {
+ return NGX_ERROR;
+ }
+ }
+
+ *pos = last;
+
+ return NGX_OK;
+}
+
+
+/* RFC 8941, Section 4.2.1.1: an Item or an Inner List, each with Parameters */
+
+static ngx_int_t
+ngx_http_priority_parse_value(u_char **pos, u_char *end, ngx_int_t *type,
+ ngx_int_t *value)
+{
+ u_char *last;
+
+ last = *pos;
+
+ if (last < end && *last == '(') {
+ *type = NGX_HTTP_PRIORITY_OTHER;
+ *value = 0;
+
+ if (ngx_http_priority_parse_inner_list(&last, end) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ } else {
+ if (ngx_http_priority_parse_bare_item(&last, end, type, value)
+ != NGX_OK)
+ {
+ return NGX_ERROR;
+ }
+ }
+
+ if (ngx_http_priority_parse_params(&last, end) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ *pos = last;
+
+ return NGX_OK;
+}
+
+
+/* RFC 8941, Section 4.2.3.3 */
+
+static ngx_int_t
+ngx_http_priority_parse_key(u_char **pos, u_char *end, ngx_str_t *key)
+{
+ u_char *last, ch;
+
+ last = *pos;
+
+ if (last == end) {
+ return NGX_ERROR;
+ }
+
+ ch = *last;
+
+ if (!((ch >= 'a' && ch <= 'z') || ch == '*')) {
+ return NGX_ERROR;
+ }
+
+ key->data = last;
+
+ do {
+ last++;
+
+ if (last == end) {
+ break;
+ }
+
+ ch = *last;
+
+ } while ((ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')
+ || ch == '_' || ch == '-' || ch == '.' || ch == '*');
+
+ key->len = last - *pos;
+ *pos = last;
+
+ return NGX_OK;
+}
+
+
+/* RFC 8941, Section 4.2.3.2 */
+
+static ngx_int_t
+ngx_http_priority_parse_params(u_char **pos, u_char *end)
+{
+ u_char *last;
+ ngx_str_t key;
+ ngx_int_t type, value;
+ ngx_uint_t params;
+
+ last = *pos;
+ params = 0;
+
+ while (last < end && *last == ';') {
+ last++;
+
+ if (++params > NGX_HTTP_PRIORITY_MAX_PARAMS) {
+ return NGX_ERROR;
+ }
+
+ /* Section 4.2.3.2, step 2.3: discard leading SP */
+
+ while (last < end && *last == ' ') {
+ last++;
+ }
+
+ if (ngx_http_priority_parse_key(&last, end, &key) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ if (last < end && *last == '=') {
+ last++;
+
+ if (ngx_http_priority_parse_bare_item(&last, end, &type, &value)
+ != NGX_OK)
+ {
+ return NGX_ERROR;
+ }
+ }
+ }
+
+ *pos = last;
+
+ return NGX_OK;
+}
+
+
+/* RFC 8941, Section 4.2.1.2: Inner List */
+
+static ngx_int_t
+ngx_http_priority_parse_inner_list(u_char **pos, u_char *end)
+{
+ u_char *last;
+ ngx_int_t type, value;
+ ngx_uint_t items;
+
+ last = *pos + 1;
+ items = 0;
+
+ for ( ;; ) {
+
+ while (last < end && *last == ' ') {
+ last++;
+ }
+
+ if (last < end && *last == ')') {
+ *pos = last + 1;
+ return NGX_OK;
+ }
+
+ if (++items > NGX_HTTP_PRIORITY_MAX_INNER_ITEMS) {
+ return NGX_ERROR;
+ }
+
+ if (ngx_http_priority_parse_bare_item(&last, end, &type, &value)
+ != NGX_OK)
+ {
+ return NGX_ERROR;
+ }
+
+ if (ngx_http_priority_parse_params(&last, end) != NGX_OK) {
+ return NGX_ERROR;
+ }
+
+ if (last == end) {
+ return NGX_ERROR;
+ }
+
+ if (*last != ' ' && *last != ')') {
+ return NGX_ERROR;
+ }
+ }
+}
+
+
+/* RFC 8941, Section 4.2.3.1 */
+
+static ngx_int_t
+ngx_http_priority_parse_bare_item(u_char **pos, u_char *end, ngx_int_t *type,
+ ngx_int_t *value)
+{
+ u_char ch;
+
+ if (*pos == end) {
+ return NGX_ERROR;
+ }
+
+ ch = **pos;
+
+ if (ch == '-' || (ch >= '0' && ch <= '9')) {
+ return ngx_http_priority_parse_number(pos, end, type, value);
+ }
+
+ if (ch == '?') {
+ (*pos)++;
+
+ if (*pos == end || (**pos != '0' && **pos != '1')) {
+ return NGX_ERROR;
+ }
+
+ *type = NGX_HTTP_PRIORITY_BOOLEAN;
+ *value = (**pos == '1');
+ (*pos)++;
+
+ return NGX_OK;
+ }
+
+ *type = NGX_HTTP_PRIORITY_OTHER;
+
+ if (ch == '"') {
+ return ngx_http_priority_parse_string(pos, end);
+ }
+
+ if (ch == ':') {
+ return ngx_http_priority_parse_binary(pos, end);
+ }
+
+ if (((ch | 0x20) >= 'a' && (ch | 0x20) <= 'z') || ch == '*') {
+ return ngx_http_priority_parse_token(pos, end);
+ }
+
+ return NGX_ERROR;
+}
+
+
+/* RFC 8941, Section 4.2.4: Integer or Decimal */
+
+static ngx_int_t
+ngx_http_priority_parse_number(u_char **pos, u_char *end, ngx_int_t *type,
+ ngx_int_t *value)
+{
+ u_char *last, *start;
+ ngx_int_t n;
+ ngx_uint_t neg, decimal, digits, frac;
+
+ last = *pos;
+ neg = 0;
+
+ if (*last == '-') {
+ neg = 1;
+ last++;
+ }
+
+ start = last;
+ decimal = 0;
+ digits = 0;
+ frac = 0;
+
+ /* RFC 8941, Section 4.2.4 */
+
+ while (last < end) {
+
+ if (*last >= '0' && *last <= '9') {
+ digits++;
+
+ /* step 7.5: an Integer has at most 15 digits */
+
+ if (!decimal && digits > 15) {
+ return NGX_ERROR;
+ }
+
+ /* step 9.2: a Decimal has at most three fractional digits */
+
+ if (decimal && ++frac > 3) {
+ return NGX_ERROR;
+ }
+
+ last++;
+ continue;
+ }
+
+ /* step 8: a single "." starts the fractional part of a Decimal */
+
+ if (*last == '.' && !decimal) {
+
+ /* step 8.1: at most 12 digits before the decimal point */
+
+ if (digits == 0 || digits > 12) {
+ return NGX_ERROR;
+ }
+
+ decimal = 1;
+ last++;
+ continue;
+ }
+
+ break;
+ }
+
+ if (digits == 0) {
+ return NGX_ERROR;
+ }
+
+ if (decimal) {
+
+ /* step 9.1: a Decimal must not end with "." */
+
+ if (frac == 0) {
+ return NGX_ERROR;
+ }
+
+ /* a valid Decimal, but not an Integer: parsed and discarded */
+
+ *type = NGX_HTTP_PRIORITY_OTHER;
+ *value = 0;
+ *pos = last;
+ return NGX_OK;
+ }
+
+ n = ngx_atoi(start, last - start);
+ if (n == NGX_ERROR) {
+ return NGX_ERROR;
+ }
+
+ *type = NGX_HTTP_PRIORITY_INTEGER;
+ *value = neg ? -n : n;
+ *pos = last;
+
+ return NGX_OK;
+}
+
+
+/* RFC 8941, Section 4.2.5: String */
+
+static ngx_int_t
+ngx_http_priority_parse_string(u_char **pos, u_char *end)
+{
+ u_char *last, ch;
+ ngx_uint_t len;
+
+ last = *pos + 1;
+ len = 0;
+
+ while (last < end) {
+ ch = *last++;
+
+ if (ch == '\\') {
+ if (last == end || (*last != '"' && *last != '\\')) {
+ return NGX_ERROR;
+ }
+ last++;
+
+ if (++len > NGX_HTTP_PRIORITY_MAX_STRING) {
+ return NGX_ERROR;
+ }
+
+ continue;
+ }
+
+ if (ch == '"') {
+ *pos = last;
+ return NGX_OK;
+ }
+
+ if (ch < 0x20 || ch >= 0x7f) {
+ return NGX_ERROR;
+ }
+
+ if (++len > NGX_HTTP_PRIORITY_MAX_STRING) {
+ return NGX_ERROR;
+ }
+ }
+
+ return NGX_ERROR;
+}
+
+
+/* RFC 8941, Section 4.2.6: Token */
+
+static ngx_int_t
+ngx_http_priority_parse_token(u_char **pos, u_char *end)
+{
+ u_char *last, ch;
+
+ last = *pos + 1;
+
+ while (last < end) {
+ ch = *last;
+
+ if (ch == ':' || ch == '/'
+ || ((ch | 0x20) >= 'a' && (ch | 0x20) <= 'z')
+ || (ch >= '0' && ch <= '9')
+ || ch == '!' || ch == '#' || ch == '$' || ch == '%'
+ || ch == '&' || ch == '\'' || ch == '*' || ch == '+'
+ || ch == '-' || ch == '.' || ch == '^' || ch == '_'
+ || ch == '`' || ch == '|' || ch == '~')
+ {
+ if ((ngx_uint_t) (last - *pos) >= NGX_HTTP_PRIORITY_MAX_TOKEN) {
+ return NGX_ERROR;
+ }
+
+ last++;
+ continue;
+ }
+
+ break;
+ }
+
+ *pos = last;
+
+ return NGX_OK;
+}
+
+
+/* RFC 8941, Section 4.2.7: Byte Sequence */
+
+static ngx_int_t
+ngx_http_priority_parse_binary(u_char **pos, u_char *end)
+{
+ u_char *last, ch;
+ ngx_uint_t len;
+
+ last = *pos + 1;
+ len = 0;
+
+ while (last < end) {
+ ch = *last++;
+
+ if (ch == ':') {
+
+ /* the content has to decode: 4n + 1 characters cannot */
+
+ if (len % 4 == 1) {
+ return NGX_ERROR;
+ }
+
+ *pos = last;
+ return NGX_OK;
+ }
+
+ if (!(((ch | 0x20) >= 'a' && (ch | 0x20) <= 'z')
+ || (ch >= '0' && ch <= '9')
+ || ch == '+' || ch == '/' || ch == '='))
+ {
+ return NGX_ERROR;
+ }
+
+ if (++len > NGX_HTTP_PRIORITY_MAX_BINARY) {
+ return NGX_ERROR;
+ }
+ }
+
+ return NGX_ERROR;
+}
+
+
+void
+ngx_http_priority_state_update(ngx_http_priority_state_t *ps)
+{
+ ngx_http_priority_t *e;
+
+ e = &ps->effective;
+ *e = ps->client;
+
+ if (ps->server.urgency_set) {
+ e->urgency = ps->server.urgency;
+ e->urgency_set = 1;
+ }
+
+ if (ps->server.incremental_set) {
+ e->incremental = ps->server.incremental;
+ e->incremental_set = 1;
+ }
+}
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