linux-kernel - [PATCH 10/8] modsign: Allow password to be specified for signing key

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Date:	Tue, 19 May 2015 15:45:58 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	dhowells@...hat.com
Cc:	rusty@...tcorp.com.au, mmarek@...e.cz, mjg59@...f.ucam.org,
	keyrings@...ux-nfs.org, dmitry.kasatkin@...il.com, mcgrof@...e.com,
	linux-kernel@...r.kernel.org, dhowells@...hat.com,
	seth.forshee@...onical.com, linux-security-module@...r.kernel.org
Subject: [PATCH 10/8] modsign: Allow password to be specified for signing key

We don't want this in the Kconfig since it might then get exposed in
/proc/config.gz. So make it a parameter to Kbuild instead. This also
means we don't have to jump through hoops to strip quotes from it, as
we would if it was a config option.

Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
---
 Documentation/kbuild/kbuild.txt  |  5 +++++
 Documentation/module-signing.txt |  3 +++
 scripts/sign-file.c              | 27 ++++++++++++++++++++++++++-
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt
index 6466704..0ff6a46 100644
--- a/Documentation/kbuild/kbuild.txt
+++ b/Documentation/kbuild/kbuild.txt
@@ -174,6 +174,11 @@ The output directory is often set using "O=..." on the commandline.
 
 The value can be overridden in which case the default value is ignored.
 
+KBUILD_SIGN_PIN
+--------------------------------------------------
+This variable allows a passphrase or PIN to be passed to the sign-file
+utility when signing kernel modules, if the private key requires such.
+
 KBUILD_MODPOST_WARN
 --------------------------------------------------
 KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
diff --git a/Documentation/module-signing.txt b/Documentation/module-signing.txt
index c72702e..faaa6ea 100644
--- a/Documentation/module-signing.txt
+++ b/Documentation/module-signing.txt
@@ -194,6 +194,9 @@ The hash algorithm used does not have to match the one configured, but if it
 doesn't, you should make sure that hash algorithm is either built into the
 kernel or can be loaded without requiring itself.
 
+If the private key requires a passphrase or PIN, it can be provided in the
+$KBUILD_SIGN_PIN environment variable.
+
 
 ============================
 SIGNED MODULES AND STRIPPING
diff --git a/scripts/sign-file.c b/scripts/sign-file.c
index 39aaabe..720b9bc 100755
--- a/scripts/sign-file.c
+++ b/scripts/sign-file.c
@@ -80,6 +80,27 @@ static void drain_openssl_errors(void)
 		}					\
 	} while(0)
 
+static const char *key_pass;
+
+static int pem_pw_cb(char *buf, int len, int w, void *v)
+{
+	int pwlen;
+
+	if (!key_pass)
+		return -1;
+
+	pwlen = strlen(key_pass);
+	if (pwlen >= len)
+		return -1;
+
+	strcpy(buf, key_pass);
+
+	/* If it's wrong, don't keep trying it. */
+	key_pass = NULL;
+
+	return pwlen;
+}
+
 int main(int argc, char **argv)
 {
 	struct module_signature sig_info = { .id_type = PKEY_ID_PKCS7 };
@@ -96,9 +117,12 @@ int main(int argc, char **argv)
 	BIO *b, *bd = NULL, *bm;
 	int opt, n;
 
+	OpenSSL_add_all_algorithms();
 	ERR_load_crypto_strings();
 	ERR_clear_error();
 
+	key_pass = getenv("KBUILD_SIGN_PIN");
+
 	do {
 		opt = getopt(argc, argv, "dp");
 		switch (opt) {
@@ -132,7 +156,8 @@ int main(int argc, char **argv)
 	 */
 	b = BIO_new_file(private_key_name, "rb");
 	ERR(!b, "%s", private_key_name);
-        private_key = PEM_read_bio_PrivateKey(b, NULL, NULL, NULL);
+	private_key = PEM_read_bio_PrivateKey(b, NULL, pem_pw_cb, NULL);
+	ERR(!private_key, "%s", private_key_name);
 	BIO_free(b);
 
 	b = BIO_new_file(x509_name, "rb");
-- 
2.4.0


-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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