1 files changed, 107 insertions, 0 deletions
diff --git a/ssh/censor2.c b/ssh/censor2.c
new file mode 100644
index 00000000..31ad8149
--- /dev/null
+++ b/ssh/censor2.c
@@ -0,0 +1,107 @@
+/*
+ * Packet-censoring code for SSH-2, used to identify sensitive fields
+ * like passwords so that the logging system can avoid writing them
+ * into log files.
+ */
+
+#include <assert.h>
+
+#include "putty.h"
+#include "ssh.h"
+
+int ssh2_censor_packet(
+    const PacketLogSettings *pls, int type, bool sender_is_client,
+    ptrlen pkt, logblank_t *blanks)
+{
+    int nblanks = 0;
+    ptrlen str;
+    BinarySource src[1];
+
+    BinarySource_BARE_INIT_PL(src, pkt);
+
+    if (pls->omit_data &&
+        (type == SSH2_MSG_CHANNEL_DATA ||
+         type == SSH2_MSG_CHANNEL_EXTENDED_DATA)) {
+        /* "Session data" packets - omit the data string. */
+        get_uint32(src);              /* skip channel id */
+        if (type == SSH2_MSG_CHANNEL_EXTENDED_DATA)
+            get_uint32(src);          /* skip extended data type */
+        str = get_string(src);
+        if (!get_err(src)) {
+            assert(nblanks < MAX_BLANKS);
+            blanks[nblanks].offset = src->pos - str.len;
+            blanks[nblanks].type = PKTLOG_OMIT;
+            blanks[nblanks].len = str.len;
+            nblanks++;
+        }
+    }
+
+    if (sender_is_client && pls->omit_passwords) {
+        if (type == SSH2_MSG_USERAUTH_REQUEST) {
+            /* If this is a password packet, blank the password(s). */
+            get_string(src);              /* username */
+            get_string(src);              /* service name */
+            str = get_string(src);        /* auth method */
+            if (ptrlen_eq_string(str, "password")) {
+                get_bool(src);
+                /* Blank the password field. */
+                str = get_string(src);
+                if (!get_err(src)) {
+                    assert(nblanks < MAX_BLANKS);
+                    blanks[nblanks].offset = src->pos - str.len;
+                    blanks[nblanks].type = PKTLOG_BLANK;
+                    blanks[nblanks].len = str.len;
+                    nblanks++;
+                    /* If there's another password field beyond it
+                     * (change of password), blank that too. */
+                    str = get_string(src);
+                    if (!get_err(src))
+                        blanks[nblanks-1].len =
+                            src->pos - blanks[nblanks].offset;
+                }
+            }
+        } else if (pls->actx == SSH2_PKTCTX_KBDINTER &&
+                   type == SSH2_MSG_USERAUTH_INFO_RESPONSE) {
+            /* If this is a keyboard-interactive response packet,
+             * blank the responses. */
+            get_uint32(src);
+            assert(nblanks < MAX_BLANKS);
+            blanks[nblanks].offset = src->pos;
+            blanks[nblanks].type = PKTLOG_BLANK;
+            do {
+                str = get_string(src);
+            } while (!get_err(src));
+            blanks[nblanks].len = src->pos - blanks[nblanks].offset;
+            nblanks++;
+        } else if (type == SSH2_MSG_CHANNEL_REQUEST) {
+            /*
+             * If this is an X forwarding request packet, blank the
+             * fake auth data.
+             *
+             * Note that while we blank the X authentication data
+             * here, we don't take any special action to blank the
+             * start of an X11 channel, so using MIT-MAGIC-COOKIE-1
+             * and actually opening an X connection without having
+             * session blanking enabled is likely to leak your cookie
+             * into the log.
+             */
+            get_uint32(src);
+            str = get_string(src);
+            if (ptrlen_eq_string(str, "x11-req")) {
+                get_bool(src);
+                get_bool(src);
+                get_string(src);
+                str = get_string(src);
+                if (!get_err(src)) {
+                    assert(nblanks < MAX_BLANKS);
+                    blanks[nblanks].offset = src->pos - str.len;
+                    blanks[nblanks].type = PKTLOG_BLANK;
+                    blanks[nblanks].len = str.len;
+                    nblanks++;
+                }
+            }
+        }
+    }
+
+    return nblanks;
+}