From c65f656d75091db3087a752dbc956159392fc8f2 Mon Sep 17 00:00:00 2001
From: William Dauchy <w.dauchy@criteo.com>
Date: Tue, 26 Nov 2019 12:56:26 +0100
Subject: [PATCH] BUG/MINOR: contrib/prometheus-exporter: decode parameter and
 value only

we were decoding all substring and then parsing; this could lead to
consider & and = in decoding result as delimiters where it should not.
this patch reverses the order by first parsing and then decoding each key
and value separately.

we also stop parsing after number sign (#).

This patch should be backported to 2.1 and 2.0

Signed-off-by: William Dauchy <w.dauchy@criteo.com>
---
 .../prometheus-exporter/service-prometheus.c  | 88 +++++++++++--------
 1 file changed, 52 insertions(+), 36 deletions(-)

diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index 45a4b7aab6..0f178eb64e 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -2220,7 +2220,8 @@ static int promex_parse_uri(struct appctx *appctx, struct stream_interface *si)
 	struct channel *res = si_ic(si);
 	struct htx *req_htx, *res_htx;
 	struct htx_sl *sl;
-	const char *p, *end;
+	char *p, *key, *value;
+	const char *end;
 	struct buffer *err;
 	int default_scopes = PROMEX_FL_SCOPE_ALL;
 	int len;
@@ -2234,57 +2235,72 @@ static int promex_parse_uri(struct appctx *appctx, struct stream_interface *si)
 	if (!p)
 		goto end;
 	end = HTX_SL_REQ_UPTR(sl) + HTX_SL_REQ_ULEN(sl);
-	len = end-p;
 
-	/* Decode the query-string */
+	/* copy the query-string */
+	len = end - p;
 	chunk_reset(&trash);
 	memcpy(trash.area, p, len);
 	trash.area[len] = 0;
-	len = url_decode(trash.area);
-	if (len == -1)
-		goto error;
 	p = trash.area;
-	end = p + len;
+	end = trash.area + len;
 
 	/* Parse the query-string */
-	while (p < end) {
-		if (*p == '&')
-			++p;
-		else if (*p == 's' && (end-p) >= 6 && !memcmp(p, "scope=", 6)) {
-			default_scopes = 0; /* at least a scope defined, unset default scopes */
-			p += 6;             /* now p point on the parameter value */
-			len = 0;            /* len is the value length */
-			while ((p+len) < end && *(p+len) != '&')
-				++len;
+	while (p < end && *p && *p != '#') {
+		value = NULL;
 
-			if (len == 0)
+		/* decode parameter name */
+		key = p;
+		while (p < end && *p != '=' && *p != '&' && *p != '#')
+			++p;
+		/* found a value */
+		if (*p == '=') {
+			*(p++) = 0;
+			value = p;
+		}
+		else if (*p == '&')
+			*(p++) = 0;
+		else if (*p == '#')
+			*p = 0;
+		len = url_decode(key);
+		if (len == -1)
+			goto error;
+
+		/* decode value */
+		if (value) {
+			while (p < end && *p != '=' && *p != '&' && *p != '#')
+				++p;
+			if (*p == '=')
+				goto error;
+			if (*p == '&')
+				*(p++) = 0;
+			else if (*p == '#')
+				*p = 0;
+			len = url_decode(value);
+			if (len == -1)
+				goto error;
+		}
+
+		if (!strcmp(key, "scope")) {
+			default_scopes = 0; /* at least a scope defined, unset default scopes */
+			if (!value)
+				goto error;
+			else if (*value == 0)
 				appctx->ctx.stats.flags &= ~PROMEX_FL_SCOPE_ALL;
-			else if (len == 1 && *p == '*')
+			else if (*value == '*')
 				appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_ALL;
-			else if (len == 6) {
-				if (!memcmp(p, "global", len))
-					appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_GLOBAL;
-				else if (!memcmp(p, "server", len))
-					appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_SERVER;
-			}
-			else if (len == 7 && !memcmp(p, "backend", len))
+			else if (!strcmp(value, "global"))
+				appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_GLOBAL;
+			else if (!strcmp(value, "server"))
+				appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_SERVER;
+			else if (!strcmp(value, "backend"))
 				appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_BACK;
-			else if (len == 8 && !memcmp(p, "frontend", len))
+			else if (!strcmp(value, "frontend"))
 				appctx->ctx.stats.flags |= PROMEX_FL_SCOPE_FRONT;
 			else
 				goto error;
-
-			p += len;
 		}
-		else if (*p == 'n' && (end-p) >= 8 && !memcmp(p, "no-maint", 8)) {
+		else if (!strcmp(key, "no-maint"))
 			appctx->ctx.stats.flags |= PROMEX_FL_NO_MAINT_SRV;
-			p += 8;
-		}
-		else {
-			/* ignore all other params for now */
-			while (p < end && *p != '&')
-				p++;
-		}
 	}
 
   end: