[PATCH] fetch: Strip usernames from url's before storing them

[Andreas Ericsson <ae@op5.se>]

When pulling from a remote, the full URL including username
is by default added to the commit message. Since it adds
very little value but could be used by malicious people to
glean valid usernames (with matching hostnames), we're far
better off just stripping the username before storing the
remote URL locally.

Signed-off-by: Andreas Ericsson <ae@op5.se>
---
 builtin-fetch.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/builtin-fetch.c b/builtin-fetch.c
index 3c998ea..47fba00 100644
--- a/builtin-fetch.c
+++ b/builtin-fetch.c
@@ -289,7 +289,48 @@ static int update_local_ref(struct ref *ref,
 	}
 }
 
-static int store_updated_refs(const char *url, const char *remote_name,
+/*
+ * strip username information from the url
+ * This will allocate a new string, or return its argument
+ * if no stripping is necessary.
+ *
+ * The url's we want to catch are the following:
+ *   ssh://[user@]host.xz[:port]/path/to/repo.git/
+ *   [user@]host.xz:/path/to/repo.git/
+ *   http[s]://[user[:password]@]host.xz/path/to/repo.git
+ *
+ * Although git doesn't currently support giving the password
+ * to http url's on the command-line, it's easier to catch
+ * that case too than it is to cater for it specially.
+ */
+static char *anonymize_url(const char *url)
+{
+	char *anon_url;
+	const char *at_sign = strchr(url, '@');
+	size_t prefix_len = 0;
+
+	if (!at_sign)
+		return strdup(url);
+
+	if (!prefixcmp(url, "ssh://"))
+		prefix_len = strlen("ssh://");
+	else if (!prefixcmp(url, "http://"))
+		prefix_len = strlen("http://");
+	else if (!prefixcmp(url, "https://"))
+		prefix_len = strlen("https://");
+	else if (!strchr(at_sign + 1, ':'))
+		return strdup(url);
+
+	anon_url = xcalloc(1, 1 + prefix_len +
+			   ((unsigned long)at_sign - (unsigned long)url));
+	if (prefix_len)
+		memcpy(anon_url, url, prefix_len);
+	memcpy(anon_url + prefix_len, at_sign + 1, strlen(at_sign + 1));
+
+	return anon_url;
+}
+
+static int store_updated_refs(const char *raw_url, const char *remote_name,
 		struct ref *ref_map)
 {
 	FILE *fp;
@@ -298,11 +339,13 @@ static int store_updated_refs(const char *url, const char *remote_name,
 	char note[1024];
 	const char *what, *kind;
 	struct ref *rm;
-	char *filename = git_path("FETCH_HEAD");
+	char *url, *filename = git_path("FETCH_HEAD");
 
 	fp = fopen(filename, "a");
 	if (!fp)
 		return error("cannot open %s: %s\n", filename, strerror(errno));
+
+	url = anonymize_url(raw_url);
 	for (rm = ref_map; rm; rm = rm->next) {
 		struct ref *ref = NULL;
 
@@ -376,6 +419,7 @@ static int store_updated_refs(const char *url, const char *remote_name,
 				fprintf(stderr, " %s\n", note);
 		}
 	}
+	free(url);
 	fclose(fp);
 	if (rc & 2)
 		error("some local refs could not be updated; try running\n"
-- 
1.6.3.rc0.2.g7cd31