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243 lines
8.8 KiB
243 lines
8.8 KiB
From a0a68b99d131741c1867cff321424892838fc4b3 Mon Sep 17 00:00:00 2001
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From: Yann Ylavic <ylavic@apache.org>
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Date: Sat, 27 Jul 2024 13:35:53 +0000
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Subject: [PATCH] mod_rewrite: Better question mark tracking to avoid
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UnsafeAllow3F. PR 69197.
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Track in do_expand() whether a '?' in the uri-path comes from a literal in
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the substitution string or from an expansion (variable, lookup, ...).
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In the former case it's safe to assume that it's the query-string separator
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but for the other case it's not (could be a decoded %3f from r->uri).
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This allows to avoid [UnsafeAllow3F] for most cases.
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Merges r1919325 from trunk
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Reviewed by: ylavic, covener, jorton
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Github: closes #462
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git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1919545 13f79535-47bb-0310-9956-ffa450edef68
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---
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modules/mappers/mod_rewrite.c | 107 ++++++++++++++++++++++++++++------
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1 file changed, 89 insertions(+), 18 deletions(-)
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diff --git a/modules/mappers/mod_rewrite.c b/modules/mappers/mod_rewrite.c
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index f1c22e3235b..53fb1e91ffb 100644
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--- a/modules/mappers/mod_rewrite.c
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+++ b/modules/mappers/mod_rewrite.c
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@@ -2376,9 +2376,16 @@ static APR_INLINE char *find_char_in_curlies(char *s, int c)
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* of an earlier expansion to include expansion specifiers that
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* are interpreted by a later expansion, producing results that
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* were not intended by the administrator.
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+ *
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+ * unsafe_qmark if not NULL will be set to 1 or 0 if a question mark
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+ * is found respectively in a literal or in a lookup/expansion (whether
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+ * it's the first or last qmark depends on [QSL]). Should be initialized
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+ * to -1 and remains so if no qmark is found.
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*/
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-static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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+static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry,
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+ int *unsafe_qmark)
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{
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+#define EXPAND_SPECIALS "\\$%"
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result_list *result, *current;
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result_list sresult[SMALL_EXPANSION];
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unsigned spc = 0;
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@@ -2386,8 +2393,29 @@ static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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char *p, *c;
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apr_pool_t *pool = ctx->r->pool;
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- span = strcspn(input, "\\$%");
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inputlen = strlen(input);
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+ if (!unsafe_qmark) {
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+ span = strcspn(input, EXPAND_SPECIALS);
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+ }
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+ else {
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+ span = strcspn(input, EXPAND_SPECIALS "?");
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+ if (input[span] == '?') {
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+ /* this qmark is not from an expansion thus safe */
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+ *unsafe_qmark = 0;
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+
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+ /* keep tracking only if interested in the last qmark */
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+ if (entry && (entry->flags & RULEFLAG_QSLAST)) {
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+ do {
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+ span++;
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+ span += strcspn(input + span, EXPAND_SPECIALS "?");
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+ } while (input[span] == '?');
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+ }
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+ else {
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+ unsafe_qmark = NULL;
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+ span += strcspn(input + span, EXPAND_SPECIALS);
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+ }
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+ }
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+ }
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/* fast exit */
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if (inputlen == span) {
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@@ -2405,6 +2433,8 @@ static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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/* loop for specials */
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do {
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+ int expanded = 0;
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+
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/* prepare next entry */
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if (current->len) {
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current->next = (spc < SMALL_EXPANSION)
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@@ -2450,6 +2480,8 @@ static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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current->len = span;
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current->string = p;
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outlen += span;
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+
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+ expanded = 1;
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p = endp + 1;
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}
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@@ -2489,19 +2521,18 @@ static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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}
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/* reuse of key variable as result */
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- key = lookup_map(ctx->r, map, do_expand(key, ctx, entry));
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-
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+ key = lookup_map(ctx->r, map, do_expand(key, ctx, entry, NULL));
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if (!key && dflt && *dflt) {
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- key = do_expand(dflt, ctx, entry);
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+ key = do_expand(dflt, ctx, entry, NULL);
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}
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-
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- if (key) {
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+ if (key && *key) {
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span = strlen(key);
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current->len = span;
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current->string = key;
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outlen += span;
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}
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+ expanded = 1;
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p = endp + 1;
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}
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}
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@@ -2531,8 +2562,9 @@ static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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current->len = span;
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current->string = bri->source + bri->regmatch[n].rm_so;
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}
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-
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outlen += span;
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+
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+ expanded = 1;
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}
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p += 2;
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@@ -2545,8 +2577,41 @@ static char *do_expand(char *input, rewrite_ctx *ctx, rewriterule_entry *entry)
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++outlen;
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}
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+ if (unsafe_qmark && expanded && current->len
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+ && memchr(current->string, '?', current->len)) {
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+ /* this qmark is from an expansion thus unsafe */
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+ *unsafe_qmark = 1;
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+
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+ /* keep tracking only if interested in the last qmark */
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+ if (!entry || !(entry->flags & RULEFLAG_QSLAST)) {
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+ unsafe_qmark = NULL;
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+ }
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+ }
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+
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/* check the remainder */
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- if (*p && (span = strcspn(p, "\\$%")) > 0) {
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+ if (!unsafe_qmark) {
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+ span = strcspn(p, EXPAND_SPECIALS);
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+ }
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+ else {
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+ span = strcspn(p, EXPAND_SPECIALS "?");
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+ if (p[span] == '?') {
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+ /* this qmark is not from an expansion thus safe */
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+ *unsafe_qmark = 0;
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+
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+ /* keep tracking only if interested in the last qmark */
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+ if (entry && (entry->flags & RULEFLAG_QSLAST)) {
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+ do {
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+ span++;
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+ span += strcspn(p + span, EXPAND_SPECIALS "?");
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+ } while (p[span] == '?');
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+ }
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+ else {
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+ unsafe_qmark = NULL;
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+ span += strcspn(p + span, EXPAND_SPECIALS);
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+ }
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+ }
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+ }
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+ if (span > 0) {
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if (current->len) {
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current->next = (spc < SMALL_EXPANSION)
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? &(sresult[spc++])
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@@ -2591,7 +2656,7 @@ static void do_expand_env(data_item *env, rewrite_ctx *ctx)
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char *name, *val;
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while (env) {
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- name = do_expand(env->data, ctx, NULL);
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+ name = do_expand(env->data, ctx, NULL, NULL);
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if (*name == '!') {
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name++;
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apr_table_unset(ctx->r->subprocess_env, name);
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@@ -2725,7 +2790,7 @@ static void add_cookie(request_rec *r, char *s)
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static void do_expand_cookie(data_item *cookie, rewrite_ctx *ctx)
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{
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while (cookie) {
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- add_cookie(ctx->r, do_expand(cookie->data, ctx, NULL));
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+ add_cookie(ctx->r, do_expand(cookie->data, ctx, NULL, NULL));
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cookie = cookie->next;
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}
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@@ -4014,7 +4079,7 @@ static int apply_rewrite_cond(rewritecond_entry *p, rewrite_ctx *ctx)
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int basis;
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if (p->ptype != CONDPAT_AP_EXPR)
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- input = do_expand(p->input, ctx, NULL);
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+ input = do_expand(p->input, ctx, NULL, NULL);
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switch (p->ptype) {
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case CONDPAT_FILE_EXISTS:
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@@ -4178,7 +4243,7 @@ static APR_INLINE void force_type_handler(rewriterule_entry *p,
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char *expanded;
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if (p->forced_mimetype) {
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- expanded = do_expand(p->forced_mimetype, ctx, p);
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+ expanded = do_expand(p->forced_mimetype, ctx, p, NULL);
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if (*expanded) {
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ap_str_tolower(expanded);
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@@ -4192,7 +4257,7 @@ static APR_INLINE void force_type_handler(rewriterule_entry *p,
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}
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if (p->forced_handler) {
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- expanded = do_expand(p->forced_handler, ctx, p);
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+ expanded = do_expand(p->forced_handler, ctx, p, NULL);
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if (*expanded) {
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ap_str_tolower(expanded);
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@@ -4329,12 +4394,18 @@ static rule_return_type apply_rewrite_rule(rewriterule_entry *p,
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/* expand the result */
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if (!(p->flags & RULEFLAG_NOSUB)) {
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- newuri = do_expand(p->output, ctx, p);
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+ int unsafe_qmark = -1;
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+
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+ if (p->flags & RULEFLAG_UNSAFE_ALLOW3F) {
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+ newuri = do_expand(p->output, ctx, p, NULL);
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+ }
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+ else {
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+ newuri = do_expand(p->output, ctx, p, &unsafe_qmark);
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+ }
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rewritelog((r, 2, ctx->perdir, "rewrite '%s' -> '%s'", ctx->uri,
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newuri));
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- if (!(p->flags & RULEFLAG_UNSAFE_ALLOW3F) &&
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- ap_strcasestr(r->unparsed_uri, "%3f") &&
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- ap_strchr_c(newuri, '?')) {
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+
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+ if (unsafe_qmark > 0) {
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ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(10508)
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"Unsafe URL with %%3f URL rewritten without "
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"UnsafeAllow3F");
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