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51b23565c0
httpd/httpd-2.4.37-CVE-2024-38474+.patch
Luboš Uhliarik 51b23565c0 Resolves: RHEL-45812 - httpd:2.4/httpd: Substitution encoding issue 
in mod_rewrite (CVE-2024-38474)
Resolves: RHEL-45785 - httpd:2.4/httpd: Encoding problem in
  mod_proxy (CVE-2024-38473)
Resolves: RHEL-45777 - httpd:2.4/httpd: Improper escaping of output
  in mod_rewrite (CVE-2024-38475)
Resolves: RHEL-45758 - httpd:2.4/httpd: null pointer dereference
  in mod_proxy (CVE-2024-38477)
Resolves: RHEL-45743 - httpd:2.4/httpd: Potential SSRF
  in mod_rewrite (CVE-2024-39573)
2024-07-12 00:55:48 +02:00

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diff --git a/docs/manual/mod/mod_rewrite.html.en b/docs/manual/mod/mod_rewrite.html.en
index 2b8ed35..b7f1c31 100644
--- a/docs/manual/mod/mod_rewrite.html.en
+++ b/docs/manual/mod/mod_rewrite.html.en
@@ -1403,6 +1403,16 @@ cannot use <code>$N</code> in the substitution string!
<td>Force the <a class="glossarylink" href="../glossary.html#mime-type" title="see glossary">MIME-type</a> of the target file
to be the specified type. <em><a href="../rewrite/flags.html#flag_t">details ...</a></em></td>
</tr>
+<tr>
+ <td>UnsafeAllow3F</td>
+ <td>Allows substitutions from URL's that may be unsafe.
+ <em><a href="../rewrite/flags.html#flag_unsafe_allow_3f">details ...</a></em></td>
+ </tr>
+<tr>
+ <td>UnsafePrefixStat</td>
+ <td>Allows potentially unsafe substitutions from a leading variable or backreference to a filesystem path.
+ <em><a href="../rewrite/flags.html#flag_unsafe_prefix_stat">details ...</a></em></td>
+ </tr>
</table>
<div class="note"><h3>Home directory expansion</h3>
diff --git a/docs/manual/rewrite/flags.html.en b/docs/manual/rewrite/flags.html.en
index 734809a..30d549d 100644
--- a/docs/manual/rewrite/flags.html.en
+++ b/docs/manual/rewrite/flags.html.en
@@ -768,6 +768,30 @@ re-processing (including subsequent rounds of mod_rewrite processing).
The <code>L</code> flag can be useful in this context to end the
<em>current</em> round of mod_rewrite processing.</p>
+</div>
+
+<div class="section">
+<h2><a name="flag_unsafe_allow_3f" id="flag_unsafe_allow_3f">UnsafeAllow3F</a></h2>
+
+<p>
+Setting this flag is required to allow a rewrite to continue If the
+HTTP request being written has an encoded question mark, '%3f', and the
+rewritten result has a '?' in the substiution. This protects from a malicious
+URL taking advantage of a capture and re-substitution of the encoded
+question mark.</p>
+
+</div>
+<div class="section">
+<h2><a name="flag_unsafe_prefix_status" id="flag_unsafe_prefix_status">UnsafePrefixStat</a></h2>
+
+<p>
+Setting this flag is required in server-scoped substitutions
+start with a variable or backreference and resolve to a filesystem path.
+These substitutions are not prefixed with the document root.
+This protects from a malicious URL causing the expanded substitution to
+map to an unexpected filesystem location.
+</p>
+
</div></div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/rewrite/flags.html" title="English">&nbsp;en&nbsp;</a> |
diff --git a/modules/mappers/mod_rewrite.c b/modules/mappers/mod_rewrite.c
index b71c67c..797f093 100644
--- a/modules/mappers/mod_rewrite.c
+++ b/modules/mappers/mod_rewrite.c
@@ -172,6 +172,8 @@ static const char* really_last_key = "rewrite_really_last";
#define RULEFLAG_QSLAST (1<<19)
#define RULEFLAG_QSNONE (1<<20) /* programattic only */
#define RULEFLAG_ESCAPECTLS (1<<21)
+#define RULEFLAG_UNSAFE_PREFIX_STAT (1<<22)
+#define RULEFLAG_UNSAFE_ALLOW3F (1<<23)
/* return code of the rewrite rule
* the result may be escaped - or not
@@ -179,7 +181,7 @@ static const char* really_last_key = "rewrite_really_last";
#define ACTION_NORMAL (1<<0)
#define ACTION_NOESCAPE (1<<1)
#define ACTION_STATUS (1<<2)
-
+#define ACTION_STATUS_SET (1<<3)
#define MAPTYPE_TXT (1<<0)
#define MAPTYPE_DBM (1<<1)
@@ -203,6 +205,7 @@ static const char* really_last_key = "rewrite_really_last";
#define OPTION_IGNORE_INHERIT (1<<8)
#define OPTION_IGNORE_CONTEXT_INFO (1<<9)
#define OPTION_LEGACY_PREFIX_DOCROOT (1<<10)
+#define OPTION_UNSAFE_PREFIX_STAT (1<<12)
#ifndef RAND_MAX
#define RAND_MAX 32767
@@ -296,6 +299,14 @@ typedef enum {
CONDPAT_AP_EXPR
} pattern_type;
+typedef enum {
+ RULE_RC_NOMATCH = 0, /* the rule didn't match */
+ RULE_RC_MATCH = 1, /* a matching rule w/ substitution */
+ RULE_RC_NOSUB = 2, /* a matching rule w/ no substitution */
+ RULE_RC_STATUS_SET = 3 /* a matching rule that has set an HTTP error
+ to be returned in r->status */
+} rule_return_type;
+
typedef struct {
char *input; /* Input string of RewriteCond */
char *pattern; /* the RegExp pattern string */
@@ -927,10 +938,15 @@ static void fully_qualify_uri(request_rec *r)
return;
}
+static int startsWith(request_rec *r, const char *haystack, const char *needle) {
+ int rc = (ap_strstr_c(haystack, needle) == haystack);
+ rewritelog((r, 5, NULL, "prefix_stat startsWith(%s, %s) %d", haystack, needle, rc));
+ return rc;
+}
/*
- * stat() only the first segment of a path
+ * stat() only the first segment of a path, and only if it matches the output of the last matching rule
*/
-static int prefix_stat(const char *path, apr_pool_t *pool)
+static int prefix_stat(request_rec *r, const char *path, apr_pool_t *pool, rewriterule_entry *lastsub)
{
const char *curpath = path;
const char *root;
@@ -964,10 +980,36 @@ static int prefix_stat(const char *path, apr_pool_t *pool)
apr_finfo_t sb;
if (apr_stat(&sb, statpath, APR_FINFO_MIN, pool) == APR_SUCCESS) {
- return 1;
+ if (!lastsub) {
+ rewritelog((r, 3, NULL, "prefix_stat no lastsub subst prefix %s", statpath));
+ return 1;
+ }
+
+ rewritelog((r, 3, NULL, "prefix_stat compare statpath %s and lastsub output %s STATOK %d ",
+ statpath, lastsub->output, lastsub->flags & RULEFLAG_UNSAFE_PREFIX_STAT));
+ if (lastsub->flags & RULEFLAG_UNSAFE_PREFIX_STAT) {
+ return 1;
+ }
+ else {
+ const char *docroot = ap_document_root(r);
+ const char *context_docroot = ap_context_document_root(r);
+ /*
+ * As an example, path (r->filename) is /var/foo/bar/baz.html
+ * even if the flag is not set, we can accept a rule that
+ * began with a literal /var (stapath), or if the entire path
+ * starts with the docroot or context document root
+ */
+ if (startsWith(r, lastsub->output, statpath) ||
+ startsWith(r, path, docroot) ||
+ ((docroot != context_docroot) &&
+ startsWith(r, path, context_docroot))) {
+ return 1;
+ }
+ }
}
}
+ /* prefix will be added */
return 0;
}
@@ -3046,6 +3088,9 @@ static const char *cmd_rewriteoptions(cmd_parms *cmd,
else if (!strcasecmp(w, "legacyprefixdocroot")) {
options |= OPTION_LEGACY_PREFIX_DOCROOT;
}
+ else if (!strcasecmp(w, "UnsafePrefixStat")) {
+ options |= OPTION_UNSAFE_PREFIX_STAT;
+ }
else {
return apr_pstrcat(cmd->pool, "RewriteOptions: unknown option '",
w, "'", NULL);
@@ -3752,6 +3797,18 @@ static const char *cmd_rewriterule_setflag(apr_pool_t *p, void *_cfg,
++error;
}
break;
+ case 'u':
+ case 'U':
+ if (!strcasecmp(key, "nsafePrefixStat")){
+ cfg->flags |= (RULEFLAG_UNSAFE_PREFIX_STAT);
+ }
+ else if(!strcasecmp(key, "nsafeAllow3F")) {
+ cfg->flags |= RULEFLAG_UNSAFE_ALLOW3F;
+ }
+ else {
+ ++error;
+ }
+ break;
default:
++error;
break;
@@ -4102,7 +4159,8 @@ static APR_INLINE void force_type_handler(rewriterule_entry *p,
/*
* Apply a single RewriteRule
*/
-static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
+static rule_return_type apply_rewrite_rule(rewriterule_entry *p,
+ rewrite_ctx *ctx)
{
ap_regmatch_t regmatch[AP_MAX_REG_MATCH];
apr_array_header_t *rewriteconds;
@@ -4153,7 +4211,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
rc = !ap_regexec(p->regexp, ctx->uri, AP_MAX_REG_MATCH, regmatch, 0);
if (! (( rc && !(p->flags & RULEFLAG_NOTMATCH)) ||
(!rc && (p->flags & RULEFLAG_NOTMATCH)) ) ) {
- return 0;
+ return RULE_RC_NOMATCH;
}
/* It matched, wow! Now it's time to prepare the context structure for
@@ -4204,7 +4262,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
}
}
else if (!rc) {
- return 0;
+ return RULE_RC_NOMATCH;
}
/* If some HTTP header was involved in the condition, remember it
@@ -4224,6 +4282,15 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
newuri = do_expand(p->output, ctx, p);
rewritelog((r, 2, ctx->perdir, "rewrite '%s' -> '%s'", ctx->uri,
newuri));
+ if (!(p->flags & RULEFLAG_UNSAFE_ALLOW3F) &&
+ ap_strcasestr(r->unparsed_uri, "%3f") &&
+ ap_strchr_c(newuri, '?')) {
+ ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO()
+ "Unsafe URL with %%3f URL rewritten without "
+ "UnsafeAllow3F");
+ r->status = HTTP_FORBIDDEN;
+ return RULE_RC_STATUS_SET;
+ }
}
/* expand [E=var:val] and [CO=<cookie>] */
@@ -4241,7 +4308,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
r->status = p->forced_responsecode;
}
- return 2;
+ return RULE_RC_NOSUB;
}
/* Now adjust API's knowledge about r->filename and r->args */
@@ -4293,7 +4360,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
r->filename));
r->filename = apr_pstrcat(r->pool, "proxy:", r->filename, NULL);
- return 1;
+ return RULE_RC_MATCH;
}
/* If this rule is explicitly forced for HTTP redirection
@@ -4308,7 +4375,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
r->filename));
r->status = p->forced_responsecode;
- return 1;
+ return RULE_RC_MATCH;
}
/* Special Rewriting Feature: Self-Reduction
@@ -4330,7 +4397,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
"with %s", p->forced_responsecode, r->filename));
r->status = p->forced_responsecode;
- return 1;
+ return RULE_RC_MATCH;
}
/* Finally remember the forced mime-type */
@@ -4339,7 +4406,7 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
/* Puuhhhhhhhh... WHAT COMPLICATED STUFF ;_)
* But now we're done for this particular rule.
*/
- return 1;
+ return RULE_RC_MATCH;
}
/*
@@ -4347,13 +4414,13 @@ static int apply_rewrite_rule(rewriterule_entry *p, rewrite_ctx *ctx)
* i.e. a list of rewrite rules
*/
static int apply_rewrite_list(request_rec *r, apr_array_header_t *rewriterules,
- char *perdir)
+ char *perdir, rewriterule_entry **lastsub)
{
rewriterule_entry *entries;
rewriterule_entry *p;
int i;
int changed;
- int rc;
+ rule_return_type rc;
int s;
rewrite_ctx *ctx;
int round = 1;
@@ -4361,6 +4428,7 @@ static int apply_rewrite_list(request_rec *r, apr_array_header_t *rewriterules,
ctx = apr_palloc(r->pool, sizeof(*ctx));
ctx->perdir = perdir;
ctx->r = r;
+ *lastsub = NULL;
/*
* Iterate over all existing rules
@@ -4388,7 +4456,12 @@ static int apply_rewrite_list(request_rec *r, apr_array_header_t *rewriterules,
ctx->vary = NULL;
rc = apply_rewrite_rule(p, ctx);
- if (rc) {
+ if (rc != RULE_RC_NOMATCH) {
+
+ if (!(p->flags & RULEFLAG_NOSUB)) {
+ rewritelog((r, 2, perdir, "setting lastsub to rule with output %s", p->output));
+ *lastsub = p;
+ }
/* Catch looping rules with pathinfo growing unbounded */
if ( strlen( r->filename ) > 2*r->server->limit_req_line ) {
@@ -4408,6 +4481,12 @@ static int apply_rewrite_list(request_rec *r, apr_array_header_t *rewriterules,
apr_table_merge(r->headers_out, "Vary", ctx->vary);
}
+
+ /* Error while evaluating rule, r->status set */
+ if (RULE_RC_STATUS_SET == rc) {
+ return ACTION_STATUS_SET;
+ }
+
/*
* The rule sets the response code (implies match-only)
*/
@@ -4418,7 +4497,7 @@ static int apply_rewrite_list(request_rec *r, apr_array_header_t *rewriterules,
/*
* Indicate a change if this was not a match-only rule.
*/
- if (rc != 2) {
+ if (rc != RULE_RC_NOSUB) {
changed = ((p->flags & RULEFLAG_NOESCAPE)
? ACTION_NOESCAPE : ACTION_NORMAL);
}
@@ -4607,6 +4686,7 @@ static int hook_uri2file(request_rec *r)
int rulestatus;
void *skipdata;
const char *oargs;
+ rewriterule_entry *lastsub = NULL;
/*
* retrieve the config structures
@@ -4718,7 +4798,7 @@ static int hook_uri2file(request_rec *r)
/*
* now apply the rules ...
*/
- rulestatus = apply_rewrite_list(r, conf->rewriterules, NULL);
+ rulestatus = apply_rewrite_list(r, conf->rewriterules, NULL, &lastsub);
apr_table_setn(r->notes, "mod_rewrite_rewritten",
apr_psprintf(r->pool,"%d",rulestatus));
}
@@ -4756,6 +4836,9 @@ static int hook_uri2file(request_rec *r)
r->status = HTTP_OK;
return n;
}
+ else if (ACTION_STATUS_SET == rulestatus) {
+ return r->status;
+ }
if (to_proxyreq) {
/* it should be go on as an internal proxy request */
@@ -4875,23 +4958,29 @@ static int hook_uri2file(request_rec *r)
return HTTP_BAD_REQUEST;
}
- /* if there is no valid prefix, we call
- * the translator from the core and
- * prefix the filename with document_root
+ /* We have r->filename as a path in a server-context rewrite without
+ * the PT flag. The historical behavior is to treat it as a verbatim
+ * filesystem path iff the first component of the path exists and is
+ * readable by httpd. Otherwise, it is interpreted as DocumentRoot
+ * relative.
*
* NOTICE:
* We cannot leave out the prefix_stat because
- * - when we always prefix with document_root
- * then no absolute path can be created, e.g. via
- * emulating a ScriptAlias directive, etc.
- * - when we always NOT prefix with document_root
+ * - If we always prefix with document_root
+ * then no absolute path can could ever be used in
+ * a substitution. e.g. emulating an Alias.
+ * - If we never prefix with document_root
* then the files under document_root have to
* be references directly and document_root
* gets never used and will be a dummy parameter -
- * this is also bad
+ * this is also bad.
+ * - Later addition: This part is questionable.
+ * If we had never prefixed, users would just
+ * need %{DOCUMENT_ROOT} in substitutions or the
+ * [PT] flag.
*
* BUT:
- * Under real Unix systems this is no problem,
+ * Under real Unix systems this is no perf problem,
* because we only do stat() on the first directory
* and this gets cached by the kernel for along time!
*/
@@ -4900,7 +4989,9 @@ static int hook_uri2file(request_rec *r)
uri_reduced = apr_table_get(r->notes, "mod_rewrite_uri_reduced");
}
- if (!prefix_stat(r->filename, r->pool) || uri_reduced != NULL) {
+ if (!prefix_stat(r, r->filename, r->pool,
+ conf->options & OPTION_UNSAFE_PREFIX_STAT ? NULL : lastsub)
+ || uri_reduced != NULL) {
int res;
char *tmp = r->uri;
@@ -4945,6 +5036,7 @@ static int hook_fixup(request_rec *r)
char *ofilename, *oargs;
int is_proxyreq;
void *skipdata;
+ rewriterule_entry *lastsub;
dconf = (rewrite_perdir_conf *)ap_get_module_config(r->per_dir_config,
&rewrite_module);
@@ -5029,7 +5121,7 @@ static int hook_fixup(request_rec *r)
/*
* now apply the rules ...
*/
- rulestatus = apply_rewrite_list(r, dconf->rewriterules, dconf->directory);
+ rulestatus = apply_rewrite_list(r, dconf->rewriterules, dconf->directory, &lastsub);
if (rulestatus) {
unsigned skip_absolute = is_absolute_uri(r->filename, NULL);
int to_proxyreq = 0;
@@ -5058,6 +5150,9 @@ static int hook_fixup(request_rec *r)
r->status = HTTP_OK;
return n;
}
+ else if (ACTION_STATUS_SET == rulestatus) {
+ return r->status;
+ }
if (to_proxyreq) {
/* it should go on as an internal proxy request */
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