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/* $OpenBSD: cms.c,v 1.11 2021/10/26 10:52:49 claudio Exp $ */
/*
* Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <assert.h>
#include <err.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <openssl/cms.h>
#include "extern.h"
/*
* Parse and validate a self-signed CMS message, where the signing X509
* certificate has been hashed to dgst (optional).
* Conforms to RFC 6488.
* The eContentType of the message must be an oid object.
* Return the eContent as a string and set "rsz" to be its length.
*/
unsigned char *
cms_parse_validate(X509 **xp, const char *fn, const unsigned char *der,
size_t derlen, const ASN1_OBJECT *oid, size_t *rsz)
{
const ASN1_OBJECT *obj;
ASN1_OCTET_STRING **os = NULL;
CMS_ContentInfo *cms;
int rc = 0;
STACK_OF(X509) *certs = NULL;
unsigned char *res = NULL;
*rsz = 0;
*xp = NULL;
/* just fail for empty buffers, the warning was printed elsewhere */
if (der == NULL)
return NULL;
if ((cms = d2i_CMS_ContentInfo(NULL, &der, derlen)) == NULL) {
cryptowarnx("%s: RFC 6488: failed CMS parse", fn);
goto out;
}
/*
* The CMS is self-signed with a signing certifiate.
* Verify that the self-signage is correct.
*/
if (!CMS_verify(cms, NULL, NULL, NULL, NULL,
CMS_NO_SIGNER_CERT_VERIFY)) {
cryptowarnx("%s: RFC 6488: CMS not self-signed", fn);
goto out;
}
/* RFC 6488 section 2.1.3.1: check the object's eContentType. */
obj = CMS_get0_eContentType(cms);
if (obj == NULL) {
warnx("%s: RFC 6488 section 2.1.3.1: eContentType: "
"OID object is NULL", fn);
goto out;
}
if (OBJ_cmp(obj, oid) != 0) {
char buf[128], obuf[128];
OBJ_obj2txt(buf, sizeof(buf), obj, 1);
OBJ_obj2txt(obuf, sizeof(obuf), oid, 1);
warnx("%s: RFC 6488 section 2.1.3.1: eContentType: "
"unknown OID: %s, want %s", fn, buf, obuf);
goto out;
}
/*
* The self-signing certificate is further signed by the input
* signing authority according to RFC 6488, 2.1.4.
* We extract that certificate now for later verification.
*/
certs = CMS_get0_signers(cms);
if (certs == NULL || sk_X509_num(certs) != 1) {
warnx("%s: RFC 6488 section 2.1.4: eContent: "
"want 1 signer, have %d", fn, sk_X509_num(certs));
goto out;
}
*xp = X509_dup(sk_X509_value(certs, 0));
/* Verify that we have eContent to disseminate. */
if ((os = CMS_get0_content(cms)) == NULL || *os == NULL) {
warnx("%s: RFC 6488 section 2.1.4: "
"eContent: zero-length content", fn);
goto out;
}
/*
* Extract and duplicate the eContent.
* The CMS framework offers us no other way of easily managing
* this information; and since we're going to d2i it anyway,
* simply pass it as the desired underlying types.
*/
if ((res = malloc((*os)->length)) == NULL)
err(1, NULL);
memcpy(res, (*os)->data, (*os)->length);
*rsz = (*os)->length;
rc = 1;
out:
sk_X509_free(certs);
CMS_ContentInfo_free(cms);
if (rc == 0) {
X509_free(*xp);
*xp = NULL;
}
return res;
}
/*
* Wrapper around ASN1_get_object() that preserves the current start
* state and returns a more meaningful value.
* Return zero on failure, non-zero on success.
*/
int
ASN1_frame(const char *fn, size_t sz,
const unsigned char **cnt, long *cntsz, int *tag)
{
int ret, pcls;
ret = ASN1_get_object(cnt, cntsz, tag, &pcls, sz);
if ((ret & 0x80)) {
cryptowarnx("%s: ASN1_get_object", fn);
return 0;
}
return ASN1_object_size((ret & 0x01) ? 2 : 0, *cntsz, *tag);
}
/*
* Check the version field in eContent.
* Returns -1 on failure, zero on success.
*/
int
cms_econtent_version(const char *fn, const unsigned char **d, size_t dsz,
long *version)
{
ASN1_INTEGER *aint = NULL;
long plen;
int ptag, rc = -1;
if (!ASN1_frame(fn, dsz, d, &plen, &ptag))
goto out;
if (ptag != 0) {
warnx("%s: eContent version: expected explicit tag [0]", fn);
goto out;
}
aint = d2i_ASN1_INTEGER(NULL, d, plen);
if (aint == NULL) {
cryptowarnx("%s: eContent version: failed d2i_ASN1_INTEGER",
fn);
goto out;
}
*version = ASN1_INTEGER_get(aint);
if (*version < 0) {
warnx("%s: eContent version: expected positive integer, got:"
" %ld", fn, *version);
goto out;
}
rc = 0;
out:
ASN1_INTEGER_free(aint);
return rc;
}
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