FTP: zero terminate the entry path even on bad input

... a single double quote could leave the entry path buffer without a zero
terminating byte. CVE-2017-1000254

Test 1152 added to verify.

Reported-by: Max Dymond
Bug: https://curl.haxx.se/docs/adv_20171004.html

lib/ftp.c

@@ -2779,6 +2779,7 @@ static CURLcode ftp_statemach_act(struct connectdata *conn)
         const size_t buf_size = data->set.buffer_size;
         char *dir;
         char *store;
+        bool entry_extracted = FALSE;
 
         dir = malloc(nread + 1);
         if(!dir)
@@ -2810,7 +2811,7 @@ static CURLcode ftp_statemach_act(struct connectdata *conn)
               }
               else {
                 /* end of path */
-                *store = '\0'; /* zero terminate */
+                entry_extracted = TRUE;
                 break; /* get out of this loop */
               }
             }
@@ -2819,7 +2820,9 @@ static CURLcode ftp_statemach_act(struct connectdata *conn)
             store++;
             ptr++;
           }
-
+          *store = '\0'; /* zero terminate */
+        }
+        if(entry_extracted) {
           /* If the path name does not look like an absolute path (i.e.: it
              does not start with a '/'), we probably need some server-dependent
              adjustments. For example, this is the case when connecting to

tests/data/Makefile.inc

@@ -122,6 +122,7 @@ test1120 test1121 test1122 test1123 test1124 test1125 test1126 test1127 \
 test1128 test1129 test1130 test1131 test1132 test1133 test1134 test1135 \
 test1136 test1137 test1138 test1139 test1140 test1141 test1142 test1143 \
 test1144 test1145 test1146 test1147 test1148 test1149 test1150 test1151 \
+test1152 \
 \
 test1160 test1161 \
 test1200 test1201 test1202 test1203 test1204 test1205 test1206 test1207 \

tests/data/test1152

@@ -0,0 +1,61 @@
+<testcase>
+<info>
+<keywords>
+FTP
+PASV
+LIST
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<servercmd>
+REPLY PWD 257 "just one
+</servercmd>
+
+# When doing LIST, we get the default list output hard-coded in the test
+# FTP server
+<data mode="text">
+total 20
+drwxr-xr-x   8 98       98           512 Oct 22 13:06 .
+drwxr-xr-x   8 98       98           512 Oct 22 13:06 ..
+drwxr-xr-x   2 98       98           512 May  2  1996 curl-releases
+-r--r--r--   1 0        1             35 Jul 16  1996 README
+lrwxrwxrwx   1 0        1              7 Dec  9  1999 bin -> usr/bin
+dr-xr-xr-x   2 0        1            512 Oct  1  1997 dev
+drwxrwxrwx   2 98       98           512 May 29 16:04 download.html
+dr-xr-xr-x   2 0        1            512 Nov 30  1995 etc
+drwxrwxrwx   2 98       1            512 Oct 30 14:33 pub
+dr-xr-xr-x   5 0        1            512 Oct  1  1997 usr
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+ftp
+</server>
+ <name>
+FTP with uneven quote in PWD response
+ </name>
+ <command>
+ftp://%HOSTIP:%FTPPORT/test-1152/
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+USER anonymous
+PASS ftp@example.com
+PWD
+CWD test-1152
+EPSV
+TYPE A
+LIST
+QUIT
+</protocol>
+</verify>
+</testcase>