1 files changed, 84 insertions, 0 deletions
diff --git a/utils/sessprep.c b/utils/sessprep.c
new file mode 100644
index 00000000..95e7b658
--- /dev/null
+++ b/utils/sessprep.c
@@ -0,0 +1,84 @@
+/*
+ * sessprep.c: centralise some preprocessing done on Conf objects
+ * before launching them.
+ */
+
+#include "putty.h"
+
+void prepare_session(Conf *conf)
+{
+    char *hostbuf = dupstr(conf_get_str(conf, CONF_host));
+    char *host = hostbuf;
+    char *p, *q;
+
+    /*
+     * Trim leading whitespace from the hostname.
+     */
+    host += strspn(host, " \t");
+
+    /*
+     * See if host is of the form user@host, and separate out the
+     * username if so.
+     */
+    if (host[0] != '\0') {
+        /*
+         * Use strrchr, in case the _username_ in turn is of the form
+         * user@host, which has been known.
+         */
+        char *atsign = strrchr(host, '@');
+        if (atsign) {
+            *atsign = '\0';
+            conf_set_str(conf, CONF_username, host);
+            host = atsign + 1;
+        }
+    }
+
+    /*
+     * Trim a colon suffix off the hostname if it's there, and discard
+     * the text after it.
+     *
+     * The exact reason why we _ignore_ this text, rather than
+     * treating it as a port number, is unfortunately lost in the
+     * mists of history: the commit which originally introduced this
+     * change on 2001-05-06 was clear on _what_ it was doing but
+     * didn't bother to explain _why_. But I [SGT, 2017-12-03] suspect
+     * it has to do with priority order: what should a saved session
+     * do if its CONF_host contains 'server.example.com:123' and its
+     * CONF_port contains 456? If CONF_port contained the _default_
+     * port number then it might be a good guess that the colon suffix
+     * on the host name was intended to override that, but you don't
+     * really want to get into making heuristic judgments on that
+     * basis.
+     *
+     * (Then again, you could just as easily make the same argument
+     * about whether a 'user@' prefix on the host name should override
+     * CONF_username, which this code _does_ do. I don't have a good
+     * answer, sadly. Both these pieces of behaviour have been around
+     * for years and it would probably cause subtle breakage in all
+     * sorts of long-forgotten scripting to go changing things around
+     * now.)
+     *
+     * In order to protect unbracketed IPv6 address literals against
+     * this treatment, we do not make this change at all if there's
+     * _more_ than one (un-IPv6-bracketed) colon.
+     */
+    p = host_strchr(host, ':');
+    if (p && p == host_strrchr(host, ':')) {
+        *p = '\0';
+    }
+
+    /*
+     * Remove any remaining whitespace.
+     */
+    p = hostbuf;
+    q = host;
+    while (*q) {
+        if (*q != ' ' && *q != '\t')
+            *p++ = *q;
+        q++;
+    }
+    *p = '\0';
+
+    conf_set_str(conf, CONF_host, hostbuf);
+    sfree(hostbuf);
+}