From c72434aa085b37ae6949a038b8e00369c5342885 Mon Sep 17 00:00:00 2001 From: Viktor Szakats Date: Mon, 9 Sep 2019 18:51:16 +0000 Subject: [PATCH] add option to override non-trusted time in signature By default the non-trusted time embedded in the signature is the current time of the machine. This means that adding a signature prevents from creating reproducible/deterministic binaries. This patch resolves that by introducing the -st option where a custom time can be supplied and which will be used in the signature. By using a point in time bound to the package (e.g. release date or timestamp of a specific file in the source package - or just 0 to suppress the current time), it makes it possible to create signed binaries with reproducible/deterministic, IOW identical signatures, regardless of when the build was done. It also makes osslsigncode behaviour closer to signtool.exe, which by default creates deterministic signatures (by include no non-trusted time at all.) The patch has been used live for the last year to build curl-for-win binaries: https://github.com/curl/curl-for-win/blob/master/osslsigncode.patch It also resolves this osslsigncode bug: https://sourceforge.net/p/osslsigncode/bugs/8/#a59a --- osslsigncode.c | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-) diff --git a/osslsigncode.c b/osslsigncode.c index 433ed0e..68fe0ab 100644 --- a/osslsigncode.c +++ b/osslsigncode.c @@ -468,6 +468,18 @@ static size_t asn1_simple_hdr_len(const unsigned char *p, size_t len) return (p[1]&0x80) ? (2 + (p[1]&0x7f)) : 2; } +/* + * Add a custom timestamp to the PKCS7 structure to prevent OpenSSL adding + * the _current_ time. This allows to create a deterministic signature when + * no trusted timestamp server was specified, making osslsigncode behaviour + * similar to signtool.exe. + */ +static int pkcs7_add_custom_time(PKCS7_SIGNER_INFO *si, time_t customtimeutc) +{ + ASN1_TIME *t = ASN1_TIME_adj(NULL, customtimeutc, 0, 0); + return PKCS7_add_signed_attribute(si, NID_pkcs9_signingTime, V_ASN1_UTCTIME, t); +} + static void tohex(const unsigned char *v, char *b, int len) { int i; @@ -835,6 +847,7 @@ static void usage(const char *argv0) "\t\t[ -t [ -t ... ] [ -p ] [ -noverifypeer ] ]\n" "\t\t[ -ts [ -ts ... ] [ -p ] [ -noverifypeer ] ]\n" #endif + "\t\t[ -st ]\n" "\t\t[ -addUnauthenticatedBlob ]\n\n" "\t\t[ -nest ]\n\n" "\t\t[ -verbose ]\n\n" @@ -1249,7 +1262,7 @@ static PKCS7 *pkcs7_get_nested_signature(PKCS7 *p7, int *has_sig) * pkcs7_set_nested_signature adds the p7nest signature to p7 * as a nested signature (SPC_NESTED_SIGNATURE). */ -static int pkcs7_set_nested_signature(PKCS7 *p7, PKCS7 *p7nest) +static int pkcs7_set_nested_signature(PKCS7 *p7, PKCS7 *p7nest, int custom_ts, time_t customtimeutc) { u_char *p = NULL; int len = 0; @@ -1265,6 +1278,10 @@ static int pkcs7_set_nested_signature(PKCS7 *p7, PKCS7 *p7nest) OPENSSL_free(p); PKCS7_SIGNER_INFO *si = sk_PKCS7_SIGNER_INFO_value(p7->d.sign->signer_info, 0); + + if (custom_ts) + pkcs7_add_custom_time(si, customtimeutc); + if (PKCS7_add_attribute(si, OBJ_txt2nid(SPC_NESTED_SIGNATURE_OBJID), V_ASN1_SEQUENCE, astr) == 0) return 0; @@ -2348,6 +2365,7 @@ int main(int argc, char **argv) { PKCS7_SIGNER_INFO *si; ASN1_STRING *astr; const EVP_MD *md; + time_t customtimeutc = (time_t)0; const char *argv0 = argv[0]; static char buf[64*1024]; @@ -2510,6 +2528,9 @@ int main(int argc, char **argv) { } else if ((cmd == CMD_SIGN) && !strcmp(*argv, "-i")) { if (--argc < 1) usage(argv0); url = *(++argv); + } else if ((cmd == CMD_SIGN) && !strcmp(*argv, "-st")) { + if (--argc < 1) usage(argv0); + customtimeutc = (time_t)strtoul(*(++argv), NULL, 10); #ifdef ENABLE_CURL } else if ((cmd == CMD_SIGN || cmd == CMD_ADD) && !strcmp(*argv, "-t")) { if (--argc < 1) usage(argv0); @@ -3114,13 +3135,18 @@ int main(int argc, char **argv) { PKCS7_set_type(sig, NID_pkcs7_signed); si = NULL; - if (cert != NULL) + if (cert != NULL) { si = PKCS7_add_signature(sig, cert, pkey, md); + if (nturl == 0 && ntsurl == 0) + pkcs7_add_custom_time(si, customtimeutc); + } if (si == NULL) { for (i=0; i