crypto/pkcs7/pkcs7_x509.c - boringssl - Git at Google

 /* Copyright (c) 2017, Google Inc.
  *
  * Permission to use, copy, modify, and/or 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 <openssl/pkcs7.h>

 #include <assert.h>
 #include <limits.h>

 #include <openssl/bytestring.h>
 #include <openssl/err.h>
 #include <openssl/mem.h>
 #include <openssl/obj.h>
 #include <openssl/pem.h>
 #include <openssl/pool.h>
 #include <openssl/stack.h>
 #include <openssl/x509.h>

 #include "internal.h"
 #include "../internal.h"


 int PKCS7_get_certificates(STACK_OF(X509) *out_certs, CBS *cbs) {
   int ret = 0;
   const size_t initial_certs_len = sk_X509_num(out_certs);
   STACK_OF(CRYPTO_BUFFER) *raw = sk_CRYPTO_BUFFER_new_null();
   if (raw == NULL ||
       !PKCS7_get_raw_certificates(raw, cbs, NULL)) {
     goto err;
   }

   for (size_t i = 0; i < sk_CRYPTO_BUFFER_num(raw); i++) {
     CRYPTO_BUFFER *buf = sk_CRYPTO_BUFFER_value(raw, i);
     X509 *x509 = X509_parse_from_buffer(buf);
     if (x509 == NULL ||
         !sk_X509_push(out_certs, x509)) {
       X509_free(x509);
       goto err;
     }
   }

   ret = 1;

 err:
   sk_CRYPTO_BUFFER_pop_free(raw, CRYPTO_BUFFER_free);
   if (!ret) {
     while (sk_X509_num(out_certs) != initial_certs_len) {
       X509 *x509 = sk_X509_pop(out_certs);
       X509_free(x509);
     }
   }

   return ret;
 }

 int PKCS7_get_CRLs(STACK_OF(X509_CRL) *out_crls, CBS *cbs) {
   CBS signed_data, crls;
   uint8_t *der_bytes = NULL;
   int ret = 0, has_crls;
   const size_t initial_crls_len = sk_X509_CRL_num(out_crls);

   // See https://tools.ietf.org/html/rfc2315#section-9.1
   if (!pkcs7_parse_header(&der_bytes, &signed_data, cbs) ||
       // Even if only CRLs are included, there may be an empty certificates
       // block. OpenSSL does this, for example.
       !CBS_get_optional_asn1(
           &signed_data, NULL, NULL,
           CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0) ||
       !CBS_get_optional_asn1(
           &signed_data, &crls, &has_crls,
           CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 1)) {
     goto err;
   }

   if (!has_crls) {
     CBS_init(&crls, NULL, 0);
   }

   while (CBS_len(&crls) > 0) {
     CBS crl_data;
     X509_CRL *crl;
     const uint8_t *inp;

     if (!CBS_get_asn1_element(&crls, &crl_data, CBS_ASN1_SEQUENCE)) {
       goto err;
     }

     if (CBS_len(&crl_data) > LONG_MAX) {
       goto err;
     }
     inp = CBS_data(&crl_data);
     crl = d2i_X509_CRL(NULL, &inp, (long)CBS_len(&crl_data));
     if (!crl) {
       goto err;
     }

     assert(inp == CBS_data(&crl_data) + CBS_len(&crl_data));

     if (sk_X509_CRL_push(out_crls, crl) == 0) {
       X509_CRL_free(crl);
       goto err;
     }
   }

   ret = 1;

 err:
   OPENSSL_free(der_bytes);

   if (!ret) {
     while (sk_X509_CRL_num(out_crls) != initial_crls_len) {
       X509_CRL_free(sk_X509_CRL_pop(out_crls));
     }
   }

   return ret;
 }

 int PKCS7_get_PEM_certificates(STACK_OF(X509) *out_certs, BIO *pem_bio) {
   uint8_t *data;
   long len;
   int ret;

   // Even though we pass PEM_STRING_PKCS7 as the expected PEM type here, PEM
   // internally will actually allow several other values too, including
   // "CERTIFICATE".
   if (!PEM_bytes_read_bio(&data, &len, NULL /* PEM type output */,
                           PEM_STRING_PKCS7, pem_bio,
                           NULL /* password callback */,
                           NULL /* password callback argument */)) {
     return 0;
   }

   CBS cbs;
   CBS_init(&cbs, data, len);
   ret = PKCS7_get_certificates(out_certs, &cbs);
   OPENSSL_free(data);
   return ret;
 }

 int PKCS7_get_PEM_CRLs(STACK_OF(X509_CRL) *out_crls, BIO *pem_bio) {
   uint8_t *data;
   long len;
   int ret;

   // Even though we pass PEM_STRING_PKCS7 as the expected PEM type here, PEM
   // internally will actually allow several other values too, including
   // "CERTIFICATE".
   if (!PEM_bytes_read_bio(&data, &len, NULL /* PEM type output */,
                           PEM_STRING_PKCS7, pem_bio,
                           NULL /* password callback */,
                           NULL /* password callback argument */)) {
     return 0;
   }

   CBS cbs;
   CBS_init(&cbs, data, len);
   ret = PKCS7_get_CRLs(out_crls, &cbs);
   OPENSSL_free(data);
   return ret;
 }

 static int pkcs7_bundle_certificates_cb(CBB *out, const void *arg) {
   const STACK_OF(X509) *certs = arg;
   size_t i;
   CBB certificates;

   // See https://tools.ietf.org/html/rfc2315#section-9.1
   if (!CBB_add_asn1(out, &certificates,
                     CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0)) {
     return 0;
   }

   for (i = 0; i < sk_X509_num(certs); i++) {
     X509 *x509 = sk_X509_value(certs, i);
     uint8_t *buf;
     int len = i2d_X509(x509, NULL);

     if (len < 0 ||
         !CBB_add_space(&certificates, &buf, len) ||
         i2d_X509(x509, &buf) < 0) {
       return 0;
     }
   }

   // |certificates| is a implicitly-tagged SET OF.
   return CBB_flush_asn1_set_of(&certificates) && CBB_flush(out);
 }

 int PKCS7_bundle_certificates(CBB *out, const STACK_OF(X509) *certs) {
   return pkcs7_add_signed_data(out, /*digest_algos_cb=*/NULL,
                                pkcs7_bundle_certificates_cb,
                                /*signer_infos_cb=*/NULL, certs);
 }

 static int pkcs7_bundle_crls_cb(CBB *out, const void *arg) {
   const STACK_OF(X509_CRL) *crls = arg;
   size_t i;
   CBB crl_data;

   // See https://tools.ietf.org/html/rfc2315#section-9.1
   if (!CBB_add_asn1(out, &crl_data,
                     CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 1)) {
     return 0;
   }

   for (i = 0; i < sk_X509_CRL_num(crls); i++) {
     X509_CRL *crl = sk_X509_CRL_value(crls, i);
     uint8_t *buf;
     int len = i2d_X509_CRL(crl, NULL);

     if (len < 0 ||
         !CBB_add_space(&crl_data, &buf, len) ||
         i2d_X509_CRL(crl, &buf) < 0) {
       return 0;
     }
   }

   // |crl_data| is a implicitly-tagged SET OF.
   return CBB_flush_asn1_set_of(&crl_data) && CBB_flush(out);
 }

 int PKCS7_bundle_CRLs(CBB *out, const STACK_OF(X509_CRL) *crls) {
   return pkcs7_add_signed_data(out, /*digest_algos_cb=*/NULL,
                                pkcs7_bundle_crls_cb,
                                /*signer_infos_cb=*/NULL, crls);
 }

 static PKCS7 *pkcs7_new(CBS *cbs) {
   PKCS7 *ret = OPENSSL_zalloc(sizeof(PKCS7));
   if (ret == NULL) {
     return NULL;
   }
   ret->type = OBJ_nid2obj(NID_pkcs7_signed);
   ret->d.sign = OPENSSL_malloc(sizeof(PKCS7_SIGNED));
   if (ret->d.sign == NULL) {
     goto err;
   }
   ret->d.sign->cert = sk_X509_new_null();
   ret->d.sign->crl = sk_X509_CRL_new_null();
   CBS copy = *cbs, copy2 = *cbs;
   if (ret->d.sign->cert == NULL || ret->d.sign->crl == NULL ||
       !PKCS7_get_certificates(ret->d.sign->cert, &copy) ||
       !PKCS7_get_CRLs(ret->d.sign->crl, cbs)) {
     goto err;
   }

   if (sk_X509_num(ret->d.sign->cert) == 0) {
     sk_X509_free(ret->d.sign->cert);
     ret->d.sign->cert = NULL;
   }

   if (sk_X509_CRL_num(ret->d.sign->crl) == 0) {
     sk_X509_CRL_free(ret->d.sign->crl);
     ret->d.sign->crl = NULL;
   }

   ret->ber_len = CBS_len(&copy2) - CBS_len(cbs);
   ret->ber_bytes = OPENSSL_memdup(CBS_data(&copy2), ret->ber_len);
   if (ret->ber_bytes == NULL) {
     goto err;
   }

   return ret;

 err:
   PKCS7_free(ret);
   return NULL;
 }

 PKCS7 *d2i_PKCS7(PKCS7 **out, const uint8_t **inp,
                  size_t len) {
   CBS cbs;
   CBS_init(&cbs, *inp, len);
   PKCS7 *ret = pkcs7_new(&cbs);
   if (ret == NULL) {
     return NULL;
   }
   *inp = CBS_data(&cbs);
   if (out != NULL) {
     PKCS7_free(*out);
     *out = ret;
   }
   return ret;
 }

 PKCS7 *d2i_PKCS7_bio(BIO *bio, PKCS7 **out) {
   // Use a generous bound, to allow for PKCS#7 files containing large root sets.
   static const size_t kMaxSize = 4 * 1024 * 1024;
   uint8_t *data;
   size_t len;
   if (!BIO_read_asn1(bio, &data, &len, kMaxSize)) {
     return NULL;
   }

   CBS cbs;
   CBS_init(&cbs, data, len);
   PKCS7 *ret = pkcs7_new(&cbs);
   OPENSSL_free(data);
   if (out != NULL && ret != NULL) {
     PKCS7_free(*out);
     *out = ret;
   }
   return ret;
 }

 int i2d_PKCS7(const PKCS7 *p7, uint8_t **out) {
   if (p7->ber_len > INT_MAX) {
     OPENSSL_PUT_ERROR(PKCS8, ERR_R_OVERFLOW);
     return -1;
   }

   if (out == NULL) {
     return (int)p7->ber_len;
   }

   if (*out == NULL) {
     *out = OPENSSL_memdup(p7->ber_bytes, p7->ber_len);
     if (*out == NULL) {
       return -1;
     }
   } else {
     OPENSSL_memcpy(*out, p7->ber_bytes, p7->ber_len);
     *out += p7->ber_len;
   }
   return (int)p7->ber_len;
 }

 int i2d_PKCS7_bio(BIO *bio, const PKCS7 *p7) {
   return BIO_write_all(bio, p7->ber_bytes, p7->ber_len);
 }

 void PKCS7_free(PKCS7 *p7) {
   if (p7 == NULL) {
     return;
   }

   OPENSSL_free(p7->ber_bytes);
   ASN1_OBJECT_free(p7->type);
   // We only supported signed data.
   if (p7->d.sign != NULL) {
     sk_X509_pop_free(p7->d.sign->cert, X509_free);
     sk_X509_CRL_pop_free(p7->d.sign->crl, X509_CRL_free);
     OPENSSL_free(p7->d.sign);
   }
   OPENSSL_free(p7);
 }

 // We only support signed data, so these getters are no-ops.
 int PKCS7_type_is_data(const PKCS7 *p7) { return 0; }
 int PKCS7_type_is_digest(const PKCS7 *p7) { return 0; }
 int PKCS7_type_is_encrypted(const PKCS7 *p7) { return 0; }
 int PKCS7_type_is_enveloped(const PKCS7 *p7) { return 0; }
 int PKCS7_type_is_signed(const PKCS7 *p7) { return 1; }
 int PKCS7_type_is_signedAndEnveloped(const PKCS7 *p7) { return 0; }

 // write_sha256_ai writes an AlgorithmIdentifier for SHA-256 to
 // |digest_algos_set|.
 static int write_sha256_ai(CBB *digest_algos_set, const void *arg) {
   CBB seq;
   return CBB_add_asn1(digest_algos_set, &seq, CBS_ASN1_SEQUENCE) &&
          OBJ_nid2cbb(&seq, NID_sha256) &&  //
          // https://datatracker.ietf.org/doc/html/rfc5754#section-2
          // "Implementations MUST generate SHA2 AlgorithmIdentifiers with absent
          //  parameters."
          CBB_flush(digest_algos_set);
 }

 // sign_sha256 writes at most |max_out_sig| bytes of the signature of |data| by
 // |pkey| to |out_sig| and sets |*out_sig_len| to the number of bytes written.
 // It returns one on success or zero on error.
 static int sign_sha256(uint8_t *out_sig, size_t *out_sig_len,
                        size_t max_out_sig, EVP_PKEY *pkey, BIO *data) {
   static const size_t kBufSize = 4096;
   uint8_t *buffer = OPENSSL_malloc(kBufSize);
   if (!buffer) {
     return 0;
   }

   EVP_MD_CTX ctx;
   EVP_MD_CTX_init(&ctx);

   int ret = 0;
   if (!EVP_DigestSignInit(&ctx, NULL, EVP_sha256(), NULL, pkey)) {
     goto out;
   }

   for (;;) {
     const int n = BIO_read(data, buffer, kBufSize);
     if (n == 0) {
       break;
     } else if (n < 0 || !EVP_DigestSignUpdate(&ctx, buffer, n)) {
       goto out;
     }
   }

   *out_sig_len = max_out_sig;
   if (!EVP_DigestSignFinal(&ctx, out_sig, out_sig_len)) {
     goto out;
   }

   ret = 1;

 out:
   EVP_MD_CTX_cleanup(&ctx);
   OPENSSL_free(buffer);
   return ret;
 }

 struct signer_info_data {
   const X509 *sign_cert;
   uint8_t *signature;
   size_t signature_len;
 };

 // write_signer_info writes the SignerInfo structure from
 // https://datatracker.ietf.org/doc/html/rfc2315#section-9.2 to |out|. It
 // returns one on success or zero on error.
 static int write_signer_info(CBB *out, const void *arg) {
   const struct signer_info_data *const si_data = arg;

   int ret = 0;
   uint8_t *subject_bytes = NULL;
   uint8_t *serial_bytes = NULL;

   const int subject_len =
       i2d_X509_NAME(X509_get_subject_name(si_data->sign_cert), &subject_bytes);
   const int serial_len = i2d_ASN1_INTEGER(
       (ASN1_INTEGER *)X509_get0_serialNumber(si_data->sign_cert),
       &serial_bytes);

   CBB seq, issuer_and_serial, signing_algo, null, signature;
   if (subject_len < 0 ||
       serial_len < 0 ||
       !CBB_add_asn1(out, &seq, CBS_ASN1_SEQUENCE) ||
       // version
       !CBB_add_asn1_uint64(&seq, 1) ||
       !CBB_add_asn1(&seq, &issuer_and_serial, CBS_ASN1_SEQUENCE) ||
       !CBB_add_bytes(&issuer_and_serial, subject_bytes, subject_len) ||
       !CBB_add_bytes(&issuer_and_serial, serial_bytes, serial_len) ||
       !write_sha256_ai(&seq, NULL) ||
       !CBB_add_asn1(&seq, &signing_algo, CBS_ASN1_SEQUENCE) ||
       !OBJ_nid2cbb(&signing_algo, NID_rsaEncryption) ||
       !CBB_add_asn1(&signing_algo, &null, CBS_ASN1_NULL) ||
       !CBB_add_asn1(&seq, &signature, CBS_ASN1_OCTETSTRING) ||
       !CBB_add_bytes(&signature, si_data->signature, si_data->signature_len) ||
       !CBB_flush(out)) {
     goto out;
   }

   ret = 1;

 out:
   OPENSSL_free(subject_bytes);
   OPENSSL_free(serial_bytes);
   return ret;
 }

 PKCS7 *PKCS7_sign(X509 *sign_cert, EVP_PKEY *pkey, STACK_OF(X509) *certs,
                   BIO *data, int flags) {
   CBB cbb;
   if (!CBB_init(&cbb, 2048)) {
     return NULL;
   }

   uint8_t *der = NULL;
   size_t len;
   PKCS7 *ret = NULL;

   if (sign_cert == NULL && pkey == NULL && flags == PKCS7_DETACHED) {
     // Caller just wants to bundle certificates.
     if (!PKCS7_bundle_certificates(&cbb, certs)) {
       goto out;
     }
   } else if (sign_cert != NULL && pkey != NULL && certs == NULL &&
              data != NULL &&
              flags == (PKCS7_NOATTR | PKCS7_BINARY | PKCS7_NOCERTS |
                        PKCS7_DETACHED) &&
              EVP_PKEY_id(pkey) == NID_rsaEncryption) {
     // sign-file.c from the Linux kernel.
     const size_t signature_max_len = EVP_PKEY_size(pkey);
     struct signer_info_data si_data = {
       .sign_cert = sign_cert,
       .signature = OPENSSL_malloc(signature_max_len),
     };

     if (!si_data.signature ||
         !sign_sha256(si_data.signature, &si_data.signature_len,
                      signature_max_len, pkey, data) ||
         !pkcs7_add_signed_data(&cbb, write_sha256_ai, /*cert_crl_cb=*/NULL,
                                write_signer_info, &si_data)) {
       OPENSSL_free(si_data.signature);
       goto out;
     }
     OPENSSL_free(si_data.signature);
   } else {
     OPENSSL_PUT_ERROR(PKCS7, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
     goto out;
   }

   if (!CBB_finish(&cbb, &der, &len)) {
     goto out;
   }

   CBS cbs;
   CBS_init(&cbs, der, len);
   ret = pkcs7_new(&cbs);

 out:
   CBB_cleanup(&cbb);
   OPENSSL_free(der);
   return ret;
 }
	/* Copyright (c) 2017, Google Inc.
	*
	* Permission to use, copy, modify, and/or 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 <openssl/pkcs7.h>

	#include <assert.h>
	#include <limits.h>

	#include <openssl/bytestring.h>
	#include <openssl/err.h>
	#include <openssl/mem.h>
	#include <openssl/obj.h>
	#include <openssl/pem.h>
	#include <openssl/pool.h>
	#include <openssl/stack.h>
	#include <openssl/x509.h>

	#include "internal.h"
	#include "../internal.h"


	int PKCS7_get_certificates(STACK_OF(X509) out_certs, CBS cbs) {
	int ret = 0;
	const size_t initial_certs_len = sk_X509_num(out_certs);
	STACK_OF(CRYPTO_BUFFER) *raw = sk_CRYPTO_BUFFER_new_null();
	if (raw == NULL \|\|
	!PKCS7_get_raw_certificates(raw, cbs, NULL)) {
	goto err;
	}

	for (size_t i = 0; i < sk_CRYPTO_BUFFER_num(raw); i++) {
	CRYPTO_BUFFER *buf = sk_CRYPTO_BUFFER_value(raw, i);
	X509 *x509 = X509_parse_from_buffer(buf);
	if (x509 == NULL \|\|
	!sk_X509_push(out_certs, x509)) {
	X509_free(x509);
	goto err;
	}
	}

	ret = 1;

	err:
	sk_CRYPTO_BUFFER_pop_free(raw, CRYPTO_BUFFER_free);
	if (!ret) {
	while (sk_X509_num(out_certs) != initial_certs_len) {
	X509 *x509 = sk_X509_pop(out_certs);
	X509_free(x509);
	}
	}

	return ret;
	}

	int PKCS7_get_CRLs(STACK_OF(X509_CRL) out_crls, CBS cbs) {
	CBS signed_data, crls;
	uint8_t *der_bytes = NULL;
	int ret = 0, has_crls;
	const size_t initial_crls_len = sk_X509_CRL_num(out_crls);

	// See https://tools.ietf.org/html/rfc2315#section-9.1
	if (!pkcs7_parse_header(&der_bytes, &signed_data, cbs) \|\|
	// Even if only CRLs are included, there may be an empty certificates
	// block. OpenSSL does this, for example.
	!CBS_get_optional_asn1(
	&signed_data, NULL, NULL,
	CBS_ASN1_CONTEXT_SPECIFIC \| CBS_ASN1_CONSTRUCTED \| 0) \|\|
	!CBS_get_optional_asn1(
	&signed_data, &crls, &has_crls,
	CBS_ASN1_CONTEXT_SPECIFIC \| CBS_ASN1_CONSTRUCTED \| 1)) {
	goto err;
	}

	if (!has_crls) {
	CBS_init(&crls, NULL, 0);
	}

	while (CBS_len(&crls) > 0) {
	CBS crl_data;
	X509_CRL *crl;
	const uint8_t *inp;

	if (!CBS_get_asn1_element(&crls, &crl_data, CBS_ASN1_SEQUENCE)) {
	goto err;
	}

	if (CBS_len(&crl_data) > LONG_MAX) {
	goto err;
	}
	inp = CBS_data(&crl_data);
	crl = d2i_X509_CRL(NULL, &inp, (long)CBS_len(&crl_data));
	if (!crl) {
	goto err;
	}

	assert(inp == CBS_data(&crl_data) + CBS_len(&crl_data));

	if (sk_X509_CRL_push(out_crls, crl) == 0) {
	X509_CRL_free(crl);
	goto err;
	}
	}

	ret = 1;

	err:
	OPENSSL_free(der_bytes);

	if (!ret) {
	while (sk_X509_CRL_num(out_crls) != initial_crls_len) {
	X509_CRL_free(sk_X509_CRL_pop(out_crls));
	}
	}

	return ret;
	}

	int PKCS7_get_PEM_certificates(STACK_OF(X509) out_certs, BIO pem_bio) {
	uint8_t *data;
	long len;
	int ret;

	// Even though we pass PEM_STRING_PKCS7 as the expected PEM type here, PEM
	// internally will actually allow several other values too, including
	// "CERTIFICATE".
	if (!PEM_bytes_read_bio(&data, &len, NULL /* PEM type output */,
	PEM_STRING_PKCS7, pem_bio,
	NULL /* password callback */,
	NULL /* password callback argument */)) {
	return 0;
	}

	CBS cbs;
	CBS_init(&cbs, data, len);
	ret = PKCS7_get_certificates(out_certs, &cbs);
	OPENSSL_free(data);
	return ret;
	}

	int PKCS7_get_PEM_CRLs(STACK_OF(X509_CRL) out_crls, BIO pem_bio) {
	uint8_t *data;
	long len;
	int ret;

	// Even though we pass PEM_STRING_PKCS7 as the expected PEM type here, PEM
	// internally will actually allow several other values too, including
	// "CERTIFICATE".
	if (!PEM_bytes_read_bio(&data, &len, NULL /* PEM type output */,
	PEM_STRING_PKCS7, pem_bio,
	NULL /* password callback */,
	NULL /* password callback argument */)) {
	return 0;
	}

	CBS cbs;
	CBS_init(&cbs, data, len);
	ret = PKCS7_get_CRLs(out_crls, &cbs);
	OPENSSL_free(data);
	return ret;
	}

	static int pkcs7_bundle_certificates_cb(CBB out, const void arg) {
	const STACK_OF(X509) *certs = arg;
	size_t i;
	CBB certificates;

	// See https://tools.ietf.org/html/rfc2315#section-9.1
	if (!CBB_add_asn1(out, &certificates,
	CBS_ASN1_CONTEXT_SPECIFIC \| CBS_ASN1_CONSTRUCTED \| 0)) {
	return 0;
	}

	for (i = 0; i < sk_X509_num(certs); i++) {
	X509 *x509 = sk_X509_value(certs, i);
	uint8_t *buf;
	int len = i2d_X509(x509, NULL);

	if (len < 0 \|\|
	!CBB_add_space(&certificates, &buf, len) \|\|
	i2d_X509(x509, &buf) < 0) {
	return 0;
	}
	}

	// \|certificates\| is a implicitly-tagged SET OF.
	return CBB_flush_asn1_set_of(&certificates) && CBB_flush(out);
	}

	int PKCS7_bundle_certificates(CBB out, const STACK_OF(X509) certs) {
	return pkcs7_add_signed_data(out, /digest_algos_cb=/NULL,
	pkcs7_bundle_certificates_cb,
	/signer_infos_cb=/NULL, certs);
	}

	static int pkcs7_bundle_crls_cb(CBB out, const void arg) {
	const STACK_OF(X509_CRL) *crls = arg;
	size_t i;
	CBB crl_data;

	// See https://tools.ietf.org/html/rfc2315#section-9.1
	if (!CBB_add_asn1(out, &crl_data,
	CBS_ASN1_CONTEXT_SPECIFIC \| CBS_ASN1_CONSTRUCTED \| 1)) {
	return 0;
	}

	for (i = 0; i < sk_X509_CRL_num(crls); i++) {
	X509_CRL *crl = sk_X509_CRL_value(crls, i);
	uint8_t *buf;
	int len = i2d_X509_CRL(crl, NULL);

	if (len < 0 \|\|
	!CBB_add_space(&crl_data, &buf, len) \|\|
	i2d_X509_CRL(crl, &buf) < 0) {
	return 0;
	}
	}

	// \|crl_data\| is a implicitly-tagged SET OF.
	return CBB_flush_asn1_set_of(&crl_data) && CBB_flush(out);
	}

	int PKCS7_bundle_CRLs(CBB out, const STACK_OF(X509_CRL) crls) {
	return pkcs7_add_signed_data(out, /digest_algos_cb=/NULL,
	pkcs7_bundle_crls_cb,
	/signer_infos_cb=/NULL, crls);
	}

	static PKCS7 pkcs7_new(CBS cbs) {
	PKCS7 *ret = OPENSSL_zalloc(sizeof(PKCS7));
	if (ret == NULL) {
	return NULL;
	}
	ret->type = OBJ_nid2obj(NID_pkcs7_signed);
	ret->d.sign = OPENSSL_malloc(sizeof(PKCS7_SIGNED));
	if (ret->d.sign == NULL) {
	goto err;
	}
	ret->d.sign->cert = sk_X509_new_null();
	ret->d.sign->crl = sk_X509_CRL_new_null();
	CBS copy = cbs, copy2 = cbs;
	if (ret->d.sign->cert == NULL \|\| ret->d.sign->crl == NULL \|\|
	!PKCS7_get_certificates(ret->d.sign->cert, &copy) \|\|
	!PKCS7_get_CRLs(ret->d.sign->crl, cbs)) {
	goto err;
	}

	if (sk_X509_num(ret->d.sign->cert) == 0) {
	sk_X509_free(ret->d.sign->cert);
	ret->d.sign->cert = NULL;
	}

	if (sk_X509_CRL_num(ret->d.sign->crl) == 0) {
	sk_X509_CRL_free(ret->d.sign->crl);
	ret->d.sign->crl = NULL;
	}

	ret->ber_len = CBS_len(&copy2) - CBS_len(cbs);
	ret->ber_bytes = OPENSSL_memdup(CBS_data(&copy2), ret->ber_len);
	if (ret->ber_bytes == NULL) {
	goto err;
	}

	return ret;

	err:
	PKCS7_free(ret);
	return NULL;
	}

	PKCS7 d2i_PKCS7(PKCS7 out, const uint8_t *inp,
	size_t len) {
	CBS cbs;
	CBS_init(&cbs, *inp, len);
	PKCS7 *ret = pkcs7_new(&cbs);
	if (ret == NULL) {
	return NULL;
	}
	*inp = CBS_data(&cbs);
	if (out != NULL) {
	PKCS7_free(*out);
	*out = ret;
	}
	return ret;
	}

	PKCS7 d2i_PKCS7_bio(BIO bio, PKCS7 **out) {
	// Use a generous bound, to allow for PKCS#7 files containing large root sets.
	static const size_t kMaxSize = 4 * 1024 * 1024;
	uint8_t *data;
	size_t len;
	if (!BIO_read_asn1(bio, &data, &len, kMaxSize)) {
	return NULL;
	}

	CBS cbs;
	CBS_init(&cbs, data, len);
	PKCS7 *ret = pkcs7_new(&cbs);
	OPENSSL_free(data);
	if (out != NULL && ret != NULL) {
	PKCS7_free(*out);
	*out = ret;
	}
	return ret;
	}

	int i2d_PKCS7(const PKCS7 p7, uint8_t *out) {
	if (p7->ber_len > INT_MAX) {
	OPENSSL_PUT_ERROR(PKCS8, ERR_R_OVERFLOW);
	return -1;
	}

	if (out == NULL) {
	return (int)p7->ber_len;
	}

	if (*out == NULL) {
	*out = OPENSSL_memdup(p7->ber_bytes, p7->ber_len);
	if (*out == NULL) {
	return -1;
	}
	} else {
	OPENSSL_memcpy(*out, p7->ber_bytes, p7->ber_len);
	*out += p7->ber_len;
	}
	return (int)p7->ber_len;
	}

	int i2d_PKCS7_bio(BIO bio, const PKCS7 p7) {
	return BIO_write_all(bio, p7->ber_bytes, p7->ber_len);
	}

	void PKCS7_free(PKCS7 *p7) {
	if (p7 == NULL) {
	return;
	}

	OPENSSL_free(p7->ber_bytes);
	ASN1_OBJECT_free(p7->type);
	// We only supported signed data.
	if (p7->d.sign != NULL) {
	sk_X509_pop_free(p7->d.sign->cert, X509_free);
	sk_X509_CRL_pop_free(p7->d.sign->crl, X509_CRL_free);
	OPENSSL_free(p7->d.sign);
	}
	OPENSSL_free(p7);
	}

	// We only support signed data, so these getters are no-ops.
	int PKCS7_type_is_data(const PKCS7 *p7) { return 0; }
	int PKCS7_type_is_digest(const PKCS7 *p7) { return 0; }
	int PKCS7_type_is_encrypted(const PKCS7 *p7) { return 0; }
	int PKCS7_type_is_enveloped(const PKCS7 *p7) { return 0; }
	int PKCS7_type_is_signed(const PKCS7 *p7) { return 1; }
	int PKCS7_type_is_signedAndEnveloped(const PKCS7 *p7) { return 0; }

	// write_sha256_ai writes an AlgorithmIdentifier for SHA-256 to
	// \|digest_algos_set\|.
	static int write_sha256_ai(CBB digest_algos_set, const void arg) {
	CBB seq;
	return CBB_add_asn1(digest_algos_set, &seq, CBS_ASN1_SEQUENCE) &&
	OBJ_nid2cbb(&seq, NID_sha256) && //
	// https://datatracker.ietf.org/doc/html/rfc5754#section-2
	// "Implementations MUST generate SHA2 AlgorithmIdentifiers with absent
	// parameters."
	CBB_flush(digest_algos_set);
	}

	// sign_sha256 writes at most \|max_out_sig\| bytes of the signature of \|data\| by
	// \|pkey\| to \|out_sig\| and sets \|*out_sig_len\| to the number of bytes written.
	// It returns one on success or zero on error.
	static int sign_sha256(uint8_t out_sig, size_t out_sig_len,
	size_t max_out_sig, EVP_PKEY pkey, BIO data) {
	static const size_t kBufSize = 4096;
	uint8_t *buffer = OPENSSL_malloc(kBufSize);
	if (!buffer) {
	return 0;
	}

	EVP_MD_CTX ctx;
	EVP_MD_CTX_init(&ctx);

	int ret = 0;
	if (!EVP_DigestSignInit(&ctx, NULL, EVP_sha256(), NULL, pkey)) {
	goto out;
	}

	for (;;) {
	const int n = BIO_read(data, buffer, kBufSize);
	if (n == 0) {
	break;
	} else if (n < 0 \|\| !EVP_DigestSignUpdate(&ctx, buffer, n)) {
	goto out;
	}
	}

	*out_sig_len = max_out_sig;
	if (!EVP_DigestSignFinal(&ctx, out_sig, out_sig_len)) {
	goto out;
	}

	ret = 1;

	out:
	EVP_MD_CTX_cleanup(&ctx);
	OPENSSL_free(buffer);
	return ret;
	}

	struct signer_info_data {
	const X509 *sign_cert;
	uint8_t *signature;
	size_t signature_len;
	};

	// write_signer_info writes the SignerInfo structure from
	// https://datatracker.ietf.org/doc/html/rfc2315#section-9.2 to \|out\|. It
	// returns one on success or zero on error.
	static int write_signer_info(CBB out, const void arg) {
	const struct signer_info_data *const si_data = arg;

	int ret = 0;
	uint8_t *subject_bytes = NULL;
	uint8_t *serial_bytes = NULL;

	const int subject_len =
	i2d_X509_NAME(X509_get_subject_name(si_data->sign_cert), &subject_bytes);
	const int serial_len = i2d_ASN1_INTEGER(
	(ASN1_INTEGER *)X509_get0_serialNumber(si_data->sign_cert),
	&serial_bytes);

	CBB seq, issuer_and_serial, signing_algo, null, signature;
	if (subject_len < 0 \|\|
	serial_len < 0 \|\|
	!CBB_add_asn1(out, &seq, CBS_ASN1_SEQUENCE) \|\|
	// version
	!CBB_add_asn1_uint64(&seq, 1) \|\|
	!CBB_add_asn1(&seq, &issuer_and_serial, CBS_ASN1_SEQUENCE) \|\|
	!CBB_add_bytes(&issuer_and_serial, subject_bytes, subject_len) \|\|
	!CBB_add_bytes(&issuer_and_serial, serial_bytes, serial_len) \|\|
	!write_sha256_ai(&seq, NULL) \|\|
	!CBB_add_asn1(&seq, &signing_algo, CBS_ASN1_SEQUENCE) \|\|
	!OBJ_nid2cbb(&signing_algo, NID_rsaEncryption) \|\|
	!CBB_add_asn1(&signing_algo, &null, CBS_ASN1_NULL) \|\|
	!CBB_add_asn1(&seq, &signature, CBS_ASN1_OCTETSTRING) \|\|
	!CBB_add_bytes(&signature, si_data->signature, si_data->signature_len) \|\|
	!CBB_flush(out)) {
	goto out;
	}

	ret = 1;

	out:
	OPENSSL_free(subject_bytes);
	OPENSSL_free(serial_bytes);
	return ret;
	}

	PKCS7 PKCS7_sign(X509 sign_cert, EVP_PKEY pkey, STACK_OF(X509) certs,
	BIO *data, int flags) {
	CBB cbb;
	if (!CBB_init(&cbb, 2048)) {
	return NULL;
	}

	uint8_t *der = NULL;
	size_t len;
	PKCS7 *ret = NULL;

	if (sign_cert == NULL && pkey == NULL && flags == PKCS7_DETACHED) {
	// Caller just wants to bundle certificates.
	if (!PKCS7_bundle_certificates(&cbb, certs)) {
	goto out;
	}
	} else if (sign_cert != NULL && pkey != NULL && certs == NULL &&
	data != NULL &&
	flags == (PKCS7_NOATTR \| PKCS7_BINARY \| PKCS7_NOCERTS \|
	PKCS7_DETACHED) &&
	EVP_PKEY_id(pkey) == NID_rsaEncryption) {
	// sign-file.c from the Linux kernel.
	const size_t signature_max_len = EVP_PKEY_size(pkey);
	struct signer_info_data si_data = {
	.sign_cert = sign_cert,
	.signature = OPENSSL_malloc(signature_max_len),
	};

	if (!si_data.signature \|\|
	!sign_sha256(si_data.signature, &si_data.signature_len,
	signature_max_len, pkey, data) \|\|
	!pkcs7_add_signed_data(&cbb, write_sha256_ai, /cert_crl_cb=/NULL,
	write_signer_info, &si_data)) {
	OPENSSL_free(si_data.signature);
	goto out;
	}
	OPENSSL_free(si_data.signature);
	} else {
	OPENSSL_PUT_ERROR(PKCS7, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
	goto out;
	}

	if (!CBB_finish(&cbb, &der, &len)) {
	goto out;
	}

	CBS cbs;
	CBS_init(&cbs, der, len);
	ret = pkcs7_new(&cbs);

	out:
	CBB_cleanup(&cbb);
	OPENSSL_free(der);
	return ret;
	}