librpc/ndr/uuid.c: improve speed and accuracy of GUID string parsing

GUID_from_data_blob() was relying on sscanf to parse strings, which was
slow and quite accepting of invalid GUIDs. Instead we directly read a
fixed number of hex bytes for each field.

This now passes the samba4.local.ndr.*.guid_from_string_invalid tests.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Douglas Bagnall <dbagnall@samba.org>
Autobuild-Date(master): Wed Dec 14 08:55:42 CET 2016 on sn-devel-144

1 files changed, 111 insertions, 21 deletions

diff --git a/librpc/ndr/uuid.c b/librpc/ndr/uuid.c
index a3f68d1d344..037dd909fce 100644
--- a/librpc/ndr/uuid.c
+++ b/librpc/ndr/uuid.c
@@ -52,6 +52,102 @@ _PUBLIC_ NTSTATUS GUID_from_ndr_blob(const DATA_BLOB *b, struct GUID *guid)
 	return ndr_map_error2ntstatus(ndr_err);
 }
 
+static NTSTATUS read_hex_bytes(const char *s, uint hexchars, uint64_t *dest)
+{
+	uint64_t x = 0;
+	uint i;
+	char c;
+
+	if ((hexchars & 1) || hexchars > 16) {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	for (i = 0; i < hexchars; i++) {
+		x <<= 4;
+		c = s[i];
+		if (c >= '0' && c <= '9') {
+			x += c - '0';
+		}
+		else if (c >= 'a' && c <= 'f') {
+			x += c - 'a' + 10;
+		}
+		else if (c >= 'A' && c <= 'F') {
+			x += c - 'A' + 10;
+		}
+		else {
+			/* BAD character (including '\0') */
+			return NT_STATUS_INVALID_PARAMETER;
+		}
+	}
+	*dest = x;
+	return NT_STATUS_OK;
+}
+
+
+static NTSTATUS parse_guid_string(const char *s,
+				  uint32_t *time_low,
+				  uint32_t *time_mid,
+				  uint32_t *time_hi_and_version,
+				  uint32_t *clock_seq,
+				  uint32_t *node)
+{
+	uint64_t tmp;
+	NTSTATUS status;
+	int i;
+	/* "e12b56b6-0a95-11d1-adbb-00c04fd8d5cd"
+                |     |    |    |    |
+                |     |    |    |    \ node[6]
+                |     |    |    \_____ clock_seq[2]
+                |     |    \__________ time_hi_and_version
+		|     \_______________ time_mid
+		\_____________________ time_low
+	*/
+	status = read_hex_bytes(s, 8, &tmp);
+	if (!NT_STATUS_IS_OK(status) || s[8] != '-') {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+	*time_low = tmp;
+	s += 9;
+
+	status = read_hex_bytes(s, 4, &tmp);
+	if (!NT_STATUS_IS_OK(status) || s[4] != '-') {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+	*time_mid = tmp;
+	s += 5;
+
+	status = read_hex_bytes(s, 4, &tmp);
+	if (!NT_STATUS_IS_OK(status) || s[4] != '-') {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+	*time_hi_and_version = tmp;
+	s += 5;
+
+	for (i = 0; i < 2; i++) {
+		status = read_hex_bytes(s, 2, &tmp);
+		if (!NT_STATUS_IS_OK(status)) {
+			return NT_STATUS_INVALID_PARAMETER;
+		}
+		clock_seq[i] = tmp;
+		s += 2;
+	}
+	if (s[0] != '-') {
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	s++;
+
+	for (i = 0; i < 6; i++) {
+		status = read_hex_bytes(s, 2, &tmp);
+		if (!NT_STATUS_IS_OK(status)) {
+			return NT_STATUS_INVALID_PARAMETER;
+		}
+		node[i] = tmp;
+		s += 2;
+	}
+
+	return NT_STATUS_OK;
+}
 
 /**
   build a GUID from a string
@@ -75,32 +171,26 @@ _PUBLIC_ NTSTATUS GUID_from_data_blob(const DATA_BLOB *s, struct GUID *guid)
 	switch(s->length) {
 	case 36:
 	{
-		char string[37];
-		memcpy(string, s->data, 36);
-		string[36] = 0;
-
-		if (11 == sscanf(string,
-				 "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
-				 &time_low, &time_mid, &time_hi_and_version, 
-				 &clock_seq[0], &clock_seq[1],
-				 &node[0], &node[1], &node[2], &node[3], &node[4], &node[5])) {
-			status = NT_STATUS_OK;
-		}
+		status = parse_guid_string((char *)s->data,
+					   &time_low,
+					   &time_mid,
+					   &time_hi_and_version,
+					   clock_seq,
+					   node);
 		break;
 	}
 	case 38:
 	{
-		char string[39];
-		memcpy(string, s->data, 38);
-		string[38] = 0;
-
-		if (11 == sscanf(string, 
-				 "{%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x}",
-				 &time_low, &time_mid, &time_hi_and_version, 
-				 &clock_seq[0], &clock_seq[1],
-				 &node[0], &node[1], &node[2], &node[3], &node[4], &node[5])) {
-			status = NT_STATUS_OK;
+		if (s->data[0] != '{' || s->data[37] != '}') {
+			break;
 		}
+
+		status = parse_guid_string((char *)s->data + 1,
+					   &time_low,
+					   &time_mid,
+					   &time_hi_and_version,
+					   clock_seq,
+					   node);
 		break;
 	}
 	case 32: