From: W.C.A. Wijngaards <wouter@nlnetlabs.nl>
Date: Wed, 23 Jun 2021 12:05:59 +0000 (+0200)
Subject: - Fix #503: DNS over HTTPS response truncated.
X-Git-Tag: release-1.13.2rc1~141
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9d681b627fd874588afe60335b46c53ad3aebf67;p=thirdparty%2Funbound.git

- Fix #503: DNS over HTTPS response truncated.
---

diff --git a/doc/Changelog b/doc/Changelog
index 645667296..9ac461e5a 100644
--- a/doc/Changelog
+++ b/doc/Changelog
@@ -1,3 +1,6 @@
+23 June 2021: Wouter
+	- Fix #503: DNS over HTTPS response truncated.
+
 21 June 2021: George
 	- Fix #495: Documentation or implementation of "verbosity" option.
 
diff --git a/services/listen_dnsport.c b/services/listen_dnsport.c
index ca40fac5c..52b0a2ee9 100644
--- a/services/listen_dnsport.c
+++ b/services/listen_dnsport.c
@@ -2678,18 +2678,45 @@ static int http2_buffer_uri_query(struct http2_session* h2_session,
 		return 0;
 	}
 
-	if(!(b64len = sldns_b64url_pton(
-		(char const *)start, length,
-		sldns_buffer_current(h2_stream->qbuffer),
-		expectb64len)) || b64len < 0) {
-		lock_basic_lock(&http2_query_buffer_count_lock);
-		http2_query_buffer_count -= expectb64len;
-		lock_basic_unlock(&http2_query_buffer_count_lock);
-		sldns_buffer_free(h2_stream->qbuffer);
-		h2_stream->qbuffer = NULL;
-		/* return without error, method can be an
-		 * unknown POST */
-		return 1;
+	if(sldns_b64_contains_nonurl((char const*)start, length)) {
+		char buf[65536+4];
+		verbose(VERB_ALGO, "HTTP2 stream contains wrong b64 encoding");
+		/* copy to the scratch buffer temporarily to terminate the
+		 * string with a zero */
+		if(length+1 > sizeof(buf)) {
+			/* too long */
+			lock_basic_lock(&http2_query_buffer_count_lock);
+			http2_query_buffer_count -= expectb64len;
+			lock_basic_unlock(&http2_query_buffer_count_lock);
+			sldns_buffer_free(h2_stream->qbuffer);
+			h2_stream->qbuffer = NULL;
+			return 1;
+		}
+		memmove(buf, start, length);
+		buf[length] = 0;
+		if(!(b64len = sldns_b64_pton(buf, sldns_buffer_current(
+			h2_stream->qbuffer), expectb64len)) || b64len < 0) {
+			lock_basic_lock(&http2_query_buffer_count_lock);
+			http2_query_buffer_count -= expectb64len;
+			lock_basic_unlock(&http2_query_buffer_count_lock);
+			sldns_buffer_free(h2_stream->qbuffer);
+			h2_stream->qbuffer = NULL;
+			return 1;
+		}
+	} else {
+		if(!(b64len = sldns_b64url_pton(
+			(char const *)start, length,
+			sldns_buffer_current(h2_stream->qbuffer),
+			expectb64len)) || b64len < 0) {
+			lock_basic_lock(&http2_query_buffer_count_lock);
+			http2_query_buffer_count -= expectb64len;
+			lock_basic_unlock(&http2_query_buffer_count_lock);
+			sldns_buffer_free(h2_stream->qbuffer);
+			h2_stream->qbuffer = NULL;
+			/* return without error, method can be an
+			 * unknown POST */
+			return 1;
+		}
 	}
 	sldns_buffer_skip(h2_stream->qbuffer, (size_t)b64len);
 	return 1;
diff --git a/sldns/parseutil.c b/sldns/parseutil.c
index 9f289d359..ba71df55d 100644
--- a/sldns/parseutil.c
+++ b/sldns/parseutil.c
@@ -790,3 +790,18 @@ int sldns_b64url_pton(char const *src, size_t srcsize, uint8_t *target,
 	}
 	return sldns_b64_pton_base(src, srcsize, target, targsize, 1);
 }
+
+int sldns_b64_contains_nonurl(char const *src, size_t srcsize)
+{
+	const char* s = src;
+	while(*s && srcsize) {
+		char d = *s++;
+		srcsize--;
+		/* the '+' and the '/' and padding '=' is not allowed in b64
+		 * url encoding */
+		if(d == '+' || d == '/' || d == '=') {
+			return 1;
+		}
+	}
+	return 0;
+}
diff --git a/sldns/parseutil.h b/sldns/parseutil.h
index 7eb23317f..74d7c7275 100644
--- a/sldns/parseutil.h
+++ b/sldns/parseutil.h
@@ -102,6 +102,7 @@ size_t sldns_b64_pton_calculate_size(size_t srcsize);
 int sldns_b64_pton(char const *src, uint8_t *target, size_t targsize);
 int sldns_b64url_pton(char const *src, size_t srcsize, uint8_t *target,
 	size_t targsize);
+int sldns_b64_contains_nonurl(char const *src, size_t srcsize);
 
 /**
  * calculates the size needed to store the result of b32_ntop