system/abuild: close keyhole vulnerability

1 files changed, 72 insertions, 0 deletions

diff --git a/system/abuild/keyhole.patch b/system/abuild/keyhole.patch
new file mode 100644
index 000000000..206bd6c2e
--- /dev/null
+++ b/system/abuild/keyhole.patch
@@ -0,0 +1,72 @@
+From 4f90ce92778d0ee302e288def75591b96a397c8b Mon Sep 17 00:00:00 2001
+From: Max Rees <maxcrees@me.com>
+Date: Thu, 13 Jun 2019 23:19:54 -0400
+Subject: [PATCH] abuild-sudo: don't allow --keys-dir
+
+Not allowing --allow-untrusted is obviously a good idea, but it can be
+trivially bypassed if --keys-dir is allowed:
+
+$ abuild-apk add foo-1-r0.apk
+ERROR: foo-1-r0.apk: UNTRUSTED signature
+$ abuild-apk --allow-untrusted add foo-1-r0.apk
+abuild-apk: --allow-untrusted: not allowed option
+$ cp -rp /etc/apk/keys /tmp/keys
+$ cp untrusted.pub /tmp/keys
+$ abuild-apk --keys-dir /tmp/keys add foo-1-r0.apk
+(1/1) Installing foo (1-r0)
+OK: 4319 MiB in 806 packages
+
+If both --allow-untrusted and --keys-dir are not allowed, then it should
+no longer be possible for an unprivileged member of the abuild group to
+add an untrusted package.
+
+$ abuild-apk --keys-dir /tmp/keys add foo-1-r0.apk
+abuild-apk: --keys-dir: not allowed option
+---
+ abuild-sudo.c | 18 +++++++++++++++---
+ 1 file changed, 15 insertions(+), 3 deletions(-)
+
+diff --git a/abuild-sudo.c b/abuild-sudo.c
+index 80ceb8d7dd..12d64f13fd 100644
+--- a/abuild-sudo.c
++++ b/abuild-sudo.c
+@@ -32,6 +32,12 @@ static const char* valid_cmds[] = {
+ 	NULL
+ };
+ 
++static const char* invalid_opts[] = {
++	"--allow-untrusted",
++	"--keys-dir",
++	NULL,
++};
++
+ const char *get_command_path(const char *cmd)
+ {
+ 	const char *p;
+@@ -46,6 +52,14 @@ const char *get_command_path(const char *cmd)
+ 	return NULL;
+ }
+ 
++void check_option(const char *opt)
++{
++	int i;
++	for (i = 0; invalid_opts[i] != NULL; i++)
++		if (strcmp(opt, invalid_opts[i]) == 0)
++			errx(1, "%s: not allowed option", opt);
++}
++
+ int is_in_group(gid_t group)
+ {
+ 	int ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
+@@ -105,10 +119,8 @@ int main(int argc, const char *argv[])
+ 	if (path == NULL)
+ 		errx(1, "%s: Not a valid subcommand", cmd);
+ 
+-	/* we dont allow --allow-untrusted option */
+ 	for (i = 1; i < argc; i++)
+-		if (strcmp(argv[i], "--allow-untrusted") == 0)
+-			errx(1, "%s: not allowed option", "--allow-untrusted");
++		check_option(argv[i]);
+ 
+ 	argv[0] = path;
+ 	/* set our uid to root so bbsuid --install works */