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// Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <openssl/x509.h>
#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <string.h>
#include <openssl/asn1.h>
#include <openssl/bytestring.h>
#include <openssl/err.h>
#include <openssl/obj.h>
#include "../conf/internal.h"
#include "../internal.h"
#include "internal.h"
// Although this file is in crypto/x509 for layering purposes, it emits
// errors from the ASN.1 module for OpenSSL compatibility.
// ASN1_GEN_MAX_DEPTH is the maximum number of nested TLVs allowed.
#define ASN1_GEN_MAX_DEPTH 50
// ASN1_GEN_MAX_OUTPUT is the maximum output, in bytes, allowed. This limit is
// necessary because the SEQUENCE and SET section reference mechanism allows the
// output length to grow super-linearly with the input length.
#define ASN1_GEN_MAX_OUTPUT (64 * 1024)
// ASN1_GEN_FORMAT_* are the values for the format modifiers.
#define ASN1_GEN_FORMAT_ASCII 1
#define ASN1_GEN_FORMAT_UTF8 2
#define ASN1_GEN_FORMAT_HEX 3
#define ASN1_GEN_FORMAT_BITLIST 4
// generate_v3 converts |str| into an ASN.1 structure and writes the result to
// |cbb|. It returns one on success and zero on error. |depth| bounds recursion,
// and |format| specifies the current format modifier.
//
// If |tag| is non-zero, the structure is implicitly tagged with |tag|. |tag|
// must not have the constructed bit set.
static int generate_v3(CBB *cbb, const char *str, const X509V3_CTX *cnf,
CBS_ASN1_TAG tag, int format, int depth);
static int bitstr_cb(const char *elem, size_t len, void *bitstr);
ASN1_TYPE *ASN1_generate_v3(const char *str, const X509V3_CTX *cnf) {
bssl::ScopedCBB cbb;
if (!CBB_init(cbb.get(), 0) || //
!generate_v3(cbb.get(), str, cnf, /*tag=*/0, ASN1_GEN_FORMAT_ASCII,
/*depth=*/0)) {
return nullptr;
}
// While not strictly necessary to avoid a DoS (we rely on any super-linear
// checks being performed internally), cap the overall output to
// |ASN1_GEN_MAX_OUTPUT| so the externally-visible behavior is consistent.
if (CBB_len(cbb.get()) > ASN1_GEN_MAX_OUTPUT) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_TOO_LONG);
return nullptr;
}
const uint8_t *der = CBB_data(cbb.get());
return d2i_ASN1_TYPE(nullptr, &der, CBB_len(cbb.get()));
}
static int cbs_str_equal(const CBS *cbs, const char *str) {
return CBS_len(cbs) == strlen(str) &&
OPENSSL_memcmp(CBS_data(cbs), str, strlen(str)) == 0;
}
// parse_tag decodes a tag specifier in |cbs|. It returns the tag on success or
// zero on error.
static CBS_ASN1_TAG parse_tag(const CBS *cbs) {
CBS copy = *cbs;
uint64_t num;
if (!CBS_get_u64_decimal(&copy, &num) || num > CBS_ASN1_TAG_NUMBER_MASK) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_INVALID_NUMBER);
return 0;
}
CBS_ASN1_TAG tag_class = CBS_ASN1_CONTEXT_SPECIFIC;
// The tag may be suffixed by a class.
uint8_t c;
if (CBS_get_u8(&copy, &c)) {
switch (c) {
case 'U':
tag_class = CBS_ASN1_UNIVERSAL;
break;
case 'A':
tag_class = CBS_ASN1_APPLICATION;
break;
case 'P':
tag_class = CBS_ASN1_PRIVATE;
break;
case 'C':
tag_class = CBS_ASN1_CONTEXT_SPECIFIC;
break;
default: {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_INVALID_MODIFIER);
return 0;
}
}
if (CBS_len(&copy) != 0) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_INVALID_MODIFIER);
return 0;
}
}
// Tag [UNIVERSAL 0] is reserved for indefinite-length end-of-contents. We
// also use zero in this file to indicator no explicit tagging.
if (tag_class == CBS_ASN1_UNIVERSAL && num == 0) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_INVALID_NUMBER);
return 0;
}
return tag_class | (CBS_ASN1_TAG)num;
}
static int generate_wrapped(CBB *cbb, const char *str, const X509V3_CTX *cnf,
CBS_ASN1_TAG tag, int padding, int format,
int depth) {
CBB child;
return CBB_add_asn1(cbb, &child, tag) &&
(!padding || CBB_add_u8(&child, 0)) &&
generate_v3(&child, str, cnf, /*tag=*/0, format, depth + 1) &&
CBB_flush(cbb);
}
static int generate_v3(CBB *cbb, const char *str, const X509V3_CTX *cnf,
CBS_ASN1_TAG tag, int format, int depth) {
assert((tag & CBS_ASN1_CONSTRUCTED) == 0);
if (depth > ASN1_GEN_MAX_DEPTH) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_NESTED_TAGGING);
return 0;
}
// Process modifiers. This function uses a mix of NUL-terminated strings and
// |CBS|. Several functions only work with NUL-terminated strings, so we need
// to keep track of when a slice spans the whole buffer.
for (;;) {
// Skip whitespace.
while (*str != '\0' && OPENSSL_isspace((unsigned char)*str)) {
str++;
}
// Modifiers end at commas.
const char *comma = strchr(str, ',');
if (comma == NULL) {
break;
}
// Remove trailing whitespace.
CBS modifier;
CBS_init(&modifier, (const uint8_t *)str, comma - str);
for (;;) {
uint8_t v;
CBS copy = modifier;
if (!CBS_get_last_u8(&copy, &v) || !OPENSSL_isspace(v)) {
break;
}
modifier = copy;
}
// Advance the string past the modifier, but save the original value. We
// will need to rewind if this is not a recognized modifier.
const char *str_old = str;
str = comma + 1;
// Each modifier is either NAME:VALUE or NAME.
CBS name;
int has_value = CBS_get_until_first(&modifier, &name, ':');
if (has_value) {
CBS_skip(&modifier, 1); // Skip the colon.
} else {
name = modifier;
CBS_init(&modifier, NULL, 0);
}
if (cbs_str_equal(&name, "FORMAT") || cbs_str_equal(&name, "FORM")) {
if (cbs_str_equal(&modifier, "ASCII")) {
format = ASN1_GEN_FORMAT_ASCII;
} else if (cbs_str_equal(&modifier, "UTF8")) {
format = ASN1_GEN_FORMAT_UTF8;
} else if (cbs_str_equal(&modifier, "HEX")) {
format = ASN1_GEN_FORMAT_HEX;
} else if (cbs_str_equal(&modifier, "BITLIST")) {
format = ASN1_GEN_FORMAT_BITLIST;
} else {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_UNKNOWN_FORMAT);
return 0;
}
} else if (cbs_str_equal(&name, "IMP") ||
cbs_str_equal(&name, "IMPLICIT")) {
if (tag != 0) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_NESTED_TAGGING);
return 0;
}
tag = parse_tag(&modifier);
if (tag == 0) {
return 0;
}
} else if (cbs_str_equal(&name, "EXP") ||
cbs_str_equal(&name, "EXPLICIT")) {
// It would actually be supportable, but OpenSSL does not allow wrapping
// an explicit tag in an implicit tag.
if (tag != 0) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_NESTED_TAGGING);
return 0;
}
tag = parse_tag(&modifier);
return tag != 0 &&
generate_wrapped(cbb, str, cnf, tag | CBS_ASN1_CONSTRUCTED,
/*padding=*/0, format, depth);
} else if (cbs_str_equal(&name, "OCTWRAP")) {
tag = tag == 0 ? CBS_ASN1_OCTETSTRING : tag;
return generate_wrapped(cbb, str, cnf, tag, /*padding=*/0, format, depth);
} else if (cbs_str_equal(&name, "BITWRAP")) {
tag = tag == 0 ? CBS_ASN1_BITSTRING : tag;
return generate_wrapped(cbb, str, cnf, tag, /*padding=*/1, format, depth);
} else if (cbs_str_equal(&name, "SEQWRAP")) {
tag = tag == 0 ? CBS_ASN1_SEQUENCE : (tag | CBS_ASN1_CONSTRUCTED);
tag |= CBS_ASN1_CONSTRUCTED;
return generate_wrapped(cbb, str, cnf, tag, /*padding=*/0, format, depth);
} else if (cbs_str_equal(&name, "SETWRAP")) {
tag = tag == 0 ? CBS_ASN1_SET : (tag | CBS_ASN1_CONSTRUCTED);
return generate_wrapped(cbb, str, cnf, tag, /*padding=*/0, format, depth);
} else {
// If this was not a recognized modifier, rewind |str| to before splitting
// on the comma. The type itself consumes all remaining input.
str = str_old;
break;
}
}
// The final element is, like modifiers, NAME:VALUE or NAME, but VALUE spans
// the length of the string, including any commas.
const char *colon = strchr(str, ':');
CBS name;
const char *value;
int has_value = colon != NULL;
if (has_value) {
CBS_init(&name, (const uint8_t *)str, colon - str);
value = colon + 1;
} else {
CBS_init(&name, (const uint8_t *)str, strlen(str));
value = ""; // Most types treat missing and empty value equivalently.
}
static const struct {
const char *name;
CBS_ASN1_TAG type;
} kTypes[] = {
{"BOOL", CBS_ASN1_BOOLEAN},
{"BOOLEAN", CBS_ASN1_BOOLEAN},
{"NULL", CBS_ASN1_NULL},
{"INT", CBS_ASN1_INTEGER},
{"INTEGER", CBS_ASN1_INTEGER},
{"ENUM", CBS_ASN1_ENUMERATED},
{"ENUMERATED", CBS_ASN1_ENUMERATED},
{"OID", CBS_ASN1_OBJECT},
{"OBJECT", CBS_ASN1_OBJECT},
{"UTCTIME", CBS_ASN1_UTCTIME},
{"UTC", CBS_ASN1_UTCTIME},
{"GENERALIZEDTIME", CBS_ASN1_GENERALIZEDTIME},
{"GENTIME", CBS_ASN1_GENERALIZEDTIME},
{"OCT", CBS_ASN1_OCTETSTRING},
{"OCTETSTRING", CBS_ASN1_OCTETSTRING},
{"BITSTR", CBS_ASN1_BITSTRING},
{"BITSTRING", CBS_ASN1_BITSTRING},
{"UNIVERSALSTRING", CBS_ASN1_UNIVERSALSTRING},
{"UNIV", CBS_ASN1_UNIVERSALSTRING},
{"IA5", CBS_ASN1_IA5STRING},
{"IA5STRING", CBS_ASN1_IA5STRING},
{"UTF8", CBS_ASN1_UTF8STRING},
{"UTF8String", CBS_ASN1_UTF8STRING},
{"BMP", CBS_ASN1_BMPSTRING},
{"BMPSTRING", CBS_ASN1_BMPSTRING},
{"PRINTABLESTRING", CBS_ASN1_PRINTABLESTRING},
{"PRINTABLE", CBS_ASN1_PRINTABLESTRING},
{"T61", CBS_ASN1_T61STRING},
{"T61STRING", CBS_ASN1_T61STRING},
{"TELETEXSTRING", CBS_ASN1_T61STRING},
{"SEQUENCE", CBS_ASN1_SEQUENCE},
{"SEQ", CBS_ASN1_SEQUENCE},
{"SET", CBS_ASN1_SET},
};
CBS_ASN1_TAG type = 0;
for (size_t i = 0; i < OPENSSL_ARRAY_SIZE(kTypes); i++) {
if (cbs_str_equal(&name, kTypes[i].name)) {
type = kTypes[i].type;
break;
}
}
if (type == 0) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_UNKNOWN_TAG);
return 0;
}
// If there is an implicit tag, use the constructed bit from the base type.
tag = tag == 0 ? type : (tag | (type & CBS_ASN1_CONSTRUCTED));
CBB child;
if (!CBB_add_asn1(cbb, &child, tag)) {
return 0;
}
switch (type) {
case CBS_ASN1_NULL:
if (*value != '\0') {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_NULL_VALUE);
return 0;
}
return CBB_flush(cbb);
case CBS_ASN1_BOOLEAN: {
if (format != ASN1_GEN_FORMAT_ASCII) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_NOT_ASCII_FORMAT);
return 0;
}
ASN1_BOOLEAN boolean;
if (!X509V3_bool_from_string(value, &boolean)) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_BOOLEAN);
return 0;
}
return CBB_add_u8(&child, boolean ? 0xff : 0x00) && CBB_flush(cbb);
}
case CBS_ASN1_INTEGER:
case CBS_ASN1_ENUMERATED: {
if (format != ASN1_GEN_FORMAT_ASCII) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_INTEGER_NOT_ASCII_FORMAT);
return 0;
}
ASN1_INTEGER *obj = s2i_ASN1_INTEGER(NULL, value);
if (obj == NULL) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_INTEGER);
return 0;
}
int len = i2c_ASN1_INTEGER(obj, NULL);
uint8_t *out;
int ok = len > 0 && //
CBB_add_space(&child, &out, len) &&
i2c_ASN1_INTEGER(obj, &out) == len && CBB_flush(cbb);
ASN1_INTEGER_free(obj);
return ok;
}
case CBS_ASN1_OBJECT: {
if (format != ASN1_GEN_FORMAT_ASCII) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_OBJECT_NOT_ASCII_FORMAT);
return 0;
}
ASN1_OBJECT *obj = OBJ_txt2obj(value, /*dont_search_names=*/0);
if (obj == NULL || obj->length == 0) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_OBJECT);
return 0;
}
int ok = CBB_add_bytes(&child, obj->data, obj->length) && CBB_flush(cbb);
ASN1_OBJECT_free(obj);
return ok;
}
case CBS_ASN1_UTCTIME:
case CBS_ASN1_GENERALIZEDTIME: {
if (format != ASN1_GEN_FORMAT_ASCII) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_TIME_NOT_ASCII_FORMAT);
return 0;
}
CBS value_cbs;
CBS_init(&value_cbs, (const uint8_t *)value, strlen(value));
int ok = type == CBS_ASN1_UTCTIME
? CBS_parse_utc_time(&value_cbs, NULL,
/*allow_timezone_offset=*/0)
: CBS_parse_generalized_time(&value_cbs, NULL,
/*allow_timezone_offset=*/0);
if (!ok) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_TIME_VALUE);
return 0;
}
return CBB_add_bytes(&child, (const uint8_t *)value, strlen(value)) &&
CBB_flush(cbb);
}
case CBS_ASN1_UNIVERSALSTRING:
case CBS_ASN1_IA5STRING:
case CBS_ASN1_UTF8STRING:
case CBS_ASN1_BMPSTRING:
case CBS_ASN1_PRINTABLESTRING:
case CBS_ASN1_T61STRING: {
int encoding;
if (format == ASN1_GEN_FORMAT_ASCII) {
encoding = MBSTRING_ASC;
} else if (format == ASN1_GEN_FORMAT_UTF8) {
encoding = MBSTRING_UTF8;
} else {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_FORMAT);
return 0;
}
// |maxsize| is measured in code points, rather than bytes, but pass it in
// as a loose cap so fuzzers can exit from excessively long inputs
// earlier. This limit is not load-bearing because |ASN1_mbstring_ncopy|'s
// output is already linear in the input.
ASN1_STRING *obj = NULL;
if (ASN1_mbstring_ncopy(&obj, (const uint8_t *)value, -1, encoding,
ASN1_tag2bit(type), /*minsize=*/0,
/*maxsize=*/ASN1_GEN_MAX_OUTPUT) <= 0) {
return 0;
}
int ok = CBB_add_bytes(&child, obj->data, obj->length) && CBB_flush(cbb);
ASN1_STRING_free(obj);
return ok;
}
case CBS_ASN1_BITSTRING:
if (format == ASN1_GEN_FORMAT_BITLIST) {
ASN1_BIT_STRING *obj = ASN1_BIT_STRING_new();
if (obj == NULL) {
return 0;
}
if (!CONF_parse_list(value, ',', 1, bitstr_cb, obj)) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_LIST_ERROR);
ASN1_BIT_STRING_free(obj);
return 0;
}
int len = i2c_ASN1_BIT_STRING(obj, NULL);
uint8_t *out;
int ok = len > 0 && //
CBB_add_space(&child, &out, len) &&
i2c_ASN1_BIT_STRING(obj, &out) == len && //
CBB_flush(cbb);
ASN1_BIT_STRING_free(obj);
return ok;
}
// The other formats are the same as OCTET STRING, but with the leading
// zero bytes.
if (!CBB_add_u8(&child, 0)) {
return 0;
}
[[fallthrough]];
case CBS_ASN1_OCTETSTRING:
if (format == ASN1_GEN_FORMAT_ASCII) {
return CBB_add_bytes(&child, (const uint8_t *)value, strlen(value)) &&
CBB_flush(cbb);
}
if (format == ASN1_GEN_FORMAT_HEX) {
size_t len;
uint8_t *data = x509v3_hex_to_bytes(value, &len);
if (data == NULL) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_HEX);
return 0;
}
int ok = CBB_add_bytes(&child, data, len) && CBB_flush(cbb);
OPENSSL_free(data);
return ok;
}
OPENSSL_PUT_ERROR(ASN1, ASN1_R_ILLEGAL_BITSTRING_FORMAT);
return 0;
case CBS_ASN1_SEQUENCE:
case CBS_ASN1_SET:
if (has_value) {
if (cnf == NULL) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_SEQUENCE_OR_SET_NEEDS_CONFIG);
return 0;
}
const STACK_OF(CONF_VALUE) *section = X509V3_get_section(cnf, value);
if (section == NULL) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_SEQUENCE_OR_SET_NEEDS_CONFIG);
return 0;
}
for (size_t i = 0; i < sk_CONF_VALUE_num(section); i++) {
const CONF_VALUE *conf = sk_CONF_VALUE_value(section, i);
if (!generate_v3(&child, conf->value, cnf, /*tag=*/0,
ASN1_GEN_FORMAT_ASCII, depth + 1)) {
return 0;
}
// This recursive call, by referencing |section|, is the one place
// where |generate_v3|'s output can be super-linear in the input.
// Check bounds here.
if (CBB_len(&child) > ASN1_GEN_MAX_OUTPUT) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_TOO_LONG);
return 0;
}
}
}
if (type == CBS_ASN1_SET) {
// The SET type here is a SET OF and must be sorted.
return CBB_flush_asn1_set_of(&child) && CBB_flush(cbb);
}
return CBB_flush(cbb);
default:
OPENSSL_PUT_ERROR(ASN1, ERR_R_INTERNAL_ERROR);
return 0;
}
}
static int bitstr_cb(const char *elem, size_t len, void *bitstr) {
CBS cbs;
CBS_init(&cbs, (const uint8_t *)elem, len);
uint64_t bitnum;
if (!CBS_get_u64_decimal(&cbs, &bitnum) || CBS_len(&cbs) != 0 ||
// Cap the highest allowed bit so this mechanism cannot be used to create
// extremely large allocations with short inputs. The highest named bit in
// RFC 5280 is 8, so 256 should give comfortable margin but still only
// allow a 32-byte allocation.
//
// We do not consider this function to be safe with untrusted inputs (even
// without bugs, it is prone to string injection vulnerabilities), so DoS
// is not truly a concern, but the limit is necessary to keep fuzzing
// effective.
bitnum > 256) {
OPENSSL_PUT_ERROR(ASN1, ASN1_R_INVALID_NUMBER);
return 0;
}
if (!ASN1_BIT_STRING_set_bit(reinterpret_cast<ASN1_BIT_STRING *>(bitstr),
(int)bitnum, 1)) {
return 0;
}
return 1;
}