MODSIGN: Fix 32-bit overflow in X.509 certificate validity date checking

The current choice of lifetime for the autogenerated X.509 of 100 years,
putting the validTo date in 2112, causes problems on 32-bit systems where a
32-bit time_t wraps in 2106.  64-bit x86_64 systems seem to be unaffected.

This can result in something like:

	Loading module verification certificates
	X.509: Cert 6e03943da0f3b015ba6ed7f5e0cac4fe48680994 has expired
	MODSIGN: Problem loading in-kernel X.509 certificate (-127)

Or:

	X.509: Cert 6e03943da0f3b015ba6ed7f5e0cac4fe48680994 is not yet valid
	MODSIGN: Problem loading in-kernel X.509 certificate (-129)

Instead of turning the dates into time_t values and comparing, turn the system
clock and the ASN.1 dates into tm structs and compare those piecemeal instead.

Reported-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 12 insertions, 13 deletions

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 8fcac9493b7a5..db07e8c9c8832 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -434,11 +434,10 @@ int x509_process_extension(void *context, size_t hdrlen,
 /*
  * Record a certificate time.
  */
-static int x509_note_time(time_t *_time,  size_t hdrlen,
+static int x509_note_time(struct tm *tm,  size_t hdrlen,
 			  unsigned char tag,
 			  const unsigned char *value, size_t vlen)
 {
-	unsigned YY, MM, DD, hh, mm, ss;
 	const unsigned char *p = value;
 
 #define dec2bin(X) ((X) - '0')
@@ -448,30 +447,30 @@ static int x509_note_time(time_t *_time,  size_t hdrlen,
 		/* UTCTime: YYMMDDHHMMSSZ */
 		if (vlen != 13)
 			goto unsupported_time;
-		YY = DD2bin(p);
-		if (YY > 50)
-			YY += 1900;
+		tm->tm_year = DD2bin(p);
+		if (tm->tm_year >= 50)
+			tm->tm_year += 1900;
 		else
-			YY += 2000;
+			tm->tm_year += 2000;
 	} else if (tag == ASN1_GENTIM) {
 		/* GenTime: YYYYMMDDHHMMSSZ */
 		if (vlen != 15)
 			goto unsupported_time;
-		YY = DD2bin(p) * 100 + DD2bin(p);
+		tm->tm_year = DD2bin(p) * 100 + DD2bin(p);
 	} else {
 		goto unsupported_time;
 	}
 
-	MM = DD2bin(p);
-	DD = DD2bin(p);
-	hh = DD2bin(p);
-	mm = DD2bin(p);
-	ss = DD2bin(p);
+	tm->tm_year -= 1900;
+	tm->tm_mon  = DD2bin(p) - 1;
+	tm->tm_mday = DD2bin(p);
+	tm->tm_hour = DD2bin(p);
+	tm->tm_min  = DD2bin(p);
+	tm->tm_sec  = DD2bin(p);
 
 	if (*p != 'Z')
 		goto unsupported_time;
 
-	*_time = mktime(YY, MM, DD, hh, mm, ss);
 	return 0;
 
 unsupported_time: