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libopensc: generic parse of certificate extensions

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The code attempted to handle extensions assuming extensions were ordered. The
only extension it handled was crl's, but the handling was wrong and I didn't
find any actual use of the crl code. I've changed it to cache all the extensions
and then provided accessors functions to read a specific extension. I needed this
to read the key Usage, but the extension fetching code can work with any extension
(though the caller will need to parse the result. I also added code that parses DN
and returns a specifically requested DN component. I needed this to get the Common
Name for the certificate Subject. This gives the token a 'unique' name rather than
some generic name (like CAC-I or CAC-II). Both of these can be used to enhance the
piv support as well.

rebased by VTA
Closes #852
This commit is contained in:
Jakub Jelen 2016-08-15 13:38:29 +02:00 committed by Viktor Tarasov
parent ce82e56411
commit e4f5f84512
3 changed files with 213 additions and 16 deletions
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2
src/libopensc/opensc.h
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@ -1265,7 +1265,7 @@ int sc_format_oid(struct sc_object_id *oid, const char *in);
* Compares two sc_object_id objects
* @param oid1 the first sc_object_id object
* @param oid2 the second sc_object_id object
* @return 1 if the oids are equal and a non-zero value otherwise
* @return 1 if the oids are equal and a zero value otherwise
*/
int sc_compare_oid(const struct sc_object_id *oid1, const struct sc_object_id *oid2);
/**

209
src/libopensc/pkcs15-cert.c
View File

@ -47,16 +47,8 @@ parse_x509_cert(sc_context_t *ctx, struct sc_pkcs15_der *der, struct sc_pkcs15_c
{ "version", SC_ASN1_INTEGER, SC_ASN1_TAG_INTEGER, 0, &cert->version, NULL },
{ NULL, 0, 0, 0, NULL, NULL }
};
struct sc_asn1_entry asn1_x509v3[] = {
{ "certificatePolicies", SC_ASN1_OCTET_STRING, SC_ASN1_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, NULL, NULL },
{ "subjectKeyIdentifier", SC_ASN1_OCTET_STRING, SC_ASN1_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, NULL, NULL },
{ "crlDistributionPoints", SC_ASN1_OCTET_STRING, SC_ASN1_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL | SC_ASN1_ALLOC, &cert->crl, &cert->crl_len },
{ "authorityKeyIdentifier", SC_ASN1_OCTET_STRING, SC_ASN1_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, NULL, NULL },
{ "keyUsage", SC_ASN1_BOOLEAN, SC_ASN1_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, NULL, NULL },
{ NULL, 0, 0, 0, NULL, NULL }
};
struct sc_asn1_entry asn1_extensions[] = {
{ "x509v3", SC_ASN1_STRUCT, SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, asn1_x509v3, NULL },
{ "x509v3", SC_ASN1_OCTET_STRING, SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL| SC_ASN1_ALLOC, &cert->extensions, &cert->extensions_len },
{ NULL, 0, 0, 0, NULL, NULL }
};
struct sc_asn1_entry asn1_tbscert[] = {
@ -141,6 +133,197 @@ parse_x509_cert(sc_context_t *ctx, struct sc_pkcs15_der *der, struct sc_pkcs15_c
}
/* Get a component of Distinguished Name (e.i. subject or issuer) USING the oid tag.
* dn can be either cert->subject or cert->issuer.
* dn_len would be cert->subject_len or cert->issuer_len.
*
* Common types:
* CN: struct sc_object_id type = {{85, 4, 3, -1}};
* Country: struct sc_object_id type = {{85, 4, 6, -1}};
* L: struct sc_object_id type = {{85, 4, 7, -1}};
* S: struct sc_object_id type = {{85, 4, 8, -1}};
* O: struct sc_object_id type = {{85, 4, 10, -1}};
* OU: struct sc_object_id type = {{85, 4, 11, -1}};
*
* if *name is NULL, sc_pkcs15_get_name_from_dn will allocate space for name.
*/
int
sc_pkcs15_get_name_from_dn(struct sc_context *ctx, const u8 *dn, size_t dn_len,
const struct sc_object_id *type, u8 **name, size_t *name_len)
{
const u8 *rdn = NULL;
const u8 *next_ava = NULL;
size_t rdn_len = 0;
size_t next_ava_len = 0;
int rv;
rdn = sc_asn1_skip_tag(ctx, &dn, &dn_len, SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, &rdn_len);
if (rdn == NULL)
LOG_TEST_RET(ctx, SC_ERROR_INVALID_ASN1_OBJECT, "ASN.1 decoding of Distiguished Name");
for (next_ava = rdn, next_ava_len = rdn_len; next_ava_len; ) {
const u8 *ava, *dummy, *oidp;
struct sc_object_id oid;
size_t ava_len, dummy_len, oid_len;
/* unwrap the set and point to the next ava */
ava = sc_asn1_skip_tag(ctx, &next_ava, &next_ava_len, SC_ASN1_TAG_SET | SC_ASN1_CONS, &ava_len);
if (ava == NULL)
LOG_TEST_RET(ctx, SC_ERROR_INVALID_ASN1_OBJECT, "ASN.1 decoding of AVA");
/* It would be nice to use sc_asn1_decode here to parse the entire AVA, but we are missing 1 critical
* function in the templates: the ability to accept any tag for value. This prevents us from just
* grabbing the value as is out of the template. AVA's can have tags of PRINTABLE_STRING,
* TELETEXSTRING, T61STRING or UTF8_STRING with PRINTABLE_STRING and UTF8_STRING being the most common.
* The other feature that would be nice is returning a pointer to our requested data using the space
* of the parent (basically what this code is doing here), rather than allocating and copying.
*/
/* unwrap the sequence */
dummy = ava; dummy_len = ava_len;
ava = sc_asn1_skip_tag(ctx, &dummy, &dummy_len, SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, &ava_len);
if (ava == NULL)
LOG_TEST_RET(ctx, SC_ERROR_INVALID_ASN1_OBJECT, "ASN.1 decoding of AVA");
/* unwrap the oid */
oidp = sc_asn1_skip_tag(ctx, &ava, &ava_len, SC_ASN1_TAG_OBJECT, &oid_len);
if (ava == NULL)
LOG_TEST_RET(ctx, SC_ERROR_INVALID_ASN1_OBJECT, "ASN.1 decoding of AVA OID");
/* Convert to OID */
rv = sc_asn1_decode_object_id(oidp, oid_len, &oid);
if (rv != SC_SUCCESS)
LOG_TEST_RET(ctx, SC_ERROR_INVALID_ASN1_OBJECT, "ASN.1 decoding of AVA OID");
if (sc_compare_oid(&oid, type) == 0)
continue;
/* Yes, then return the name */
dummy = sc_asn1_skip_tag(ctx, &ava, &ava_len, ava[0] & SC_ASN1_TAG_PRIMITIVE, &dummy_len);
if (*name == NULL) {
*name = malloc(dummy_len);
if (*name == NULL)
LOG_FUNC_RETURN(ctx, SC_ERROR_OUT_OF_MEMORY);
*name_len = dummy_len;
}
*name_len = MIN(dummy_len, *name_len);
memcpy(*name, dummy, *name_len);
LOG_FUNC_RETURN(ctx, SC_SUCCESS);
}
LOG_FUNC_RETURN(ctx, SC_ERROR_ASN1_OBJECT_NOT_FOUND);
}
/* Get a specific extension from the cert.
* The extension is identified by it's oid value.
* NOTE: extensions can occur in any number or any order, which is why we
* can't parse them with a single pass of the asn1 decoder.
* If is_critical is supplied, then it is set to 1 if the extention is critical
* and 0 if it is not.
* The data in the extension is extension specific.
* The following are common extension values:
* Subject Key ID: struct sc_object_id type = {{85, 29, 14, -1}};
* Key Usage: struct sc_object_id type = {{85, 29, 15, -1}};
* Subject Alt Name: struct sc_object_id type = {{85, 29, 17, -1}};
* Basic Constraints: struct sc_object_id type = {{85, 29, 19, -1}};
* CRL Distribution Points: struct sc_object_id type = {{85, 29, 31, -1}};
* Certificate Policies: struct sc_object_id type = {{85, 29, 32, -1}};
* Extended Key Usage: struct sc_object_id type = {{85, 29, 37, -1}};
*
* if *ext_val is NULL, sc_pkcs15_get_extension will allocate space for ext_val.
*/
int
sc_pkcs15_get_extension(struct sc_context *ctx, struct sc_pkcs15_cert *cert,
const struct sc_object_id *type, u8 **ext_val,
size_t *ext_val_len, int *is_critical)
{
const u8 *ext = NULL;
const u8 *next_ext = NULL;
size_t ext_len = 0;
size_t next_ext_len = 0;
struct sc_object_id oid;
u8 *val;
size_t val_len;
int critical;
int r;
struct sc_asn1_entry asn1_cert_ext[] = {
{ "x509v3 entry OID", SC_ASN1_OBJECT, SC_ASN1_TAG_OBJECT, 0, &oid, 0 },
{ "criticalFlag", SC_ASN1_BOOLEAN, SC_ASN1_TAG_BOOLEAN, SC_ASN1_OPTIONAL, &critical, NULL },
{ "extensionValue",SC_ASN1_OCTET_STRING, SC_ASN1_TAG_OCTET_STRING, SC_ASN1_ALLOC, &val, &val_len },
{ NULL, 0, 0, 0, NULL, NULL }
};
for (next_ext = cert->extensions, next_ext_len = cert->extensions_len; next_ext_len; ) {
/* unwrap the set and point to the next ava */
ext = sc_asn1_skip_tag(ctx, &next_ext, &next_ext_len,
SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, &ext_len);
if (ext == NULL)
LOG_TEST_RET(ctx, SC_ERROR_INVALID_ASN1_OBJECT, "ASN.1 decoding of AVA");
/*
* use the sc_asn1_decoder for clarity. NOTE it would be more efficient to do this by hand
* so we avoid the man malloc/frees here, but one hopes that one day the asn1_decode will allow
* a 'static pointer' flag that returns a const pointer to the actual asn1 space so we only need
* to make a final copy of the extension value before we return */
critical = 0;
r = sc_asn1_decode(ctx, asn1_cert_ext, ext, ext_len, NULL, NULL);
if (r < 0)
LOG_FUNC_RETURN(ctx, r);
/* is it the RN we are looking for */
if(sc_compare_oid(&oid, type) != 0) {
if (*ext_val == NULL) {
*ext_val= val;
val = NULL;
*ext_val_len = val_len;
}
else {
*ext_val_len = MIN(*ext_val_len, val_len);
memcpy(*ext_val, val, *ext_val_len);
}
if (is_critical)
*is_critical = critical;
r = val_len;
free(val);
LOG_FUNC_RETURN(ctx, r);
}
free(val);
}
LOG_FUNC_RETURN(ctx, SC_ERROR_ASN1_OBJECT_NOT_FOUND);
}
/*
* Get an extension whose value is a bit string. These include keyUsage and extendedKeyUsage.
* See above for the other parameters.
*/
int
sc_pkcs15_get_bitstring_extension(struct sc_context *ctx,
struct sc_pkcs15_cert *cert, const struct sc_object_id *type,
unsigned long long *value, int *is_critical)
{
int r;
u8 *bit_string = NULL;
size_t bit_string_len=0, val_len = sizeof(*value);
struct sc_asn1_entry asn1_bit_string[] = {
{ "bitString", SC_ASN1_BIT_STRING, SC_ASN1_TAG_BIT_STRING, 0, value, &val_len },
{ NULL, 0, 0, 0, NULL, NULL }
};
r = sc_pkcs15_get_extension(ctx, cert, type, &bit_string, &bit_string_len, is_critical);
LOG_TEST_RET(ctx, r, "Get extension error");
r = sc_asn1_decode(ctx, asn1_bit_string, bit_string, bit_string_len, NULL, NULL);
LOG_TEST_RET(ctx, r, "Decoding extension bit string");
LOG_FUNC_RETURN(ctx, SC_SUCCESS);
}
int
sc_pkcs15_pubkey_from_cert(struct sc_context *ctx,
struct sc_pkcs15_der *cert_blob, struct sc_pkcs15_pubkey **out)
@ -210,9 +393,9 @@ static const struct sc_asn1_entry c_asn1_cred_ident[] = {
{ NULL, 0, 0, 0, NULL, NULL }
};
static const struct sc_asn1_entry c_asn1_com_cert_attr[] = {
{ "iD", SC_ASN1_PKCS15_ID, SC_ASN1_TAG_OCTET_STRING, 0, NULL, NULL },
{ "authority", SC_ASN1_BOOLEAN, SC_ASN1_TAG_BOOLEAN, SC_ASN1_OPTIONAL, NULL, NULL },
{ "identifier", SC_ASN1_STRUCT, SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, NULL, NULL },
{ "iD", SC_ASN1_PKCS15_ID, SC_ASN1_TAG_OCTET_STRING, 0, NULL, NULL },
{ "authority", SC_ASN1_BOOLEAN, SC_ASN1_TAG_BOOLEAN, SC_ASN1_OPTIONAL, NULL, NULL },
{ "identifier", SC_ASN1_STRUCT, SC_ASN1_TAG_SEQUENCE | SC_ASN1_CONS, SC_ASN1_OPTIONAL, NULL, NULL },
/* FIXME: Add rest of the optional fields */
{ NULL, 0, 0, 0, NULL, NULL }
};
@ -350,7 +533,7 @@ sc_pkcs15_free_certificate(struct sc_pkcs15_cert *cert)
free(cert->issuer);
free(cert->serial);
free(cert->data.value);
free(cert->crl);
free(cert->extensions);
free(cert);
}

18
src/libopensc/pkcs15.h
View File

@ -276,8 +276,8 @@ struct sc_pkcs15_cert {
size_t issuer_len;
u8 *subject;
size_t subject_len;
u8 *crl;
size_t crl_len;
u8 *extensions;
size_t extensions_len;
struct sc_pkcs15_pubkey * key;
@ -713,6 +713,20 @@ void sc_pkcs15_free_certificate(struct sc_pkcs15_cert *cert);
int sc_pkcs15_find_cert_by_id(struct sc_pkcs15_card *card,
const struct sc_pkcs15_id *id,
struct sc_pkcs15_object **out);
int sc_pkcs15_get_name_from_dn(struct sc_context *ctx,
const u8 *dn, size_t dn_len,
const struct sc_object_id *type,
u8 **name, size_t *name_len);
int sc_pkcs15_get_extension(struct sc_context *ctx,
struct sc_pkcs15_cert *cert,
const struct sc_object_id *type,
u8 **ext_val, size_t *ext_val_len,
int *is_critical);
int sc_pkcs15_get_bitstring_extension(struct sc_context *ctx,
struct sc_pkcs15_cert *cert,
const struct sc_object_id *type,
unsigned long long *value,
int *is_critical);
/* sc_pkcs15_create_cdf: Creates a new certificate DF on a card pointed
* by <card>. Information about the file, such as the file ID, is read
* from <file>. <certs> has to be NULL-terminated. */