/* X.509 certificate parser
   *
   * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #define pr_fmt(fmt) "X.509: "fmt
  #include <linux/kernel.h>

  #include <linux/export.h>

  #include <linux/slab.h>
  #include <linux/err.h>
  #include <linux/oid_registry.h>

  #include <crypto/public_key.h>

  #include "x509_parser.h"
  #include "x509-asn1.h"

  #include "x509_akid-asn1.h"

  
  struct x509_parse_context {
  	struct x509_certificate	*cert;		/* Certificate being constructed */
  	unsigned long	data;			/* Start of data */
  	const void	*cert_start;		/* Start of cert content */
  	const void	*key;			/* Key data */
  	size_t		key_size;		/* Size of key data */
  	enum OID	last_oid;		/* Last OID encountered */
  	enum OID	algo_oid;		/* Algorithm OID */
  	unsigned char	nr_mpi;			/* Number of MPIs stored */
  	u8		o_size;			/* Size of organizationName (O) */
  	u8		cn_size;		/* Size of commonName (CN) */
  	u8		email_size;		/* Size of emailAddress */
  	u16		o_offset;		/* Offset of organizationName (O) */
  	u16		cn_offset;		/* Offset of commonName (CN) */
  	u16		email_offset;		/* Offset of emailAddress */

  	unsigned	raw_akid_size;
  	const void	*raw_akid;		/* Raw authorityKeyId in ASN.1 */
  	const void	*akid_raw_issuer;	/* Raw directoryName in authorityKeyId */
  	unsigned	akid_raw_issuer_size;

  };
  
  /*
   * Free an X.509 certificate
   */
  void x509_free_certificate(struct x509_certificate *cert)
  {
  	if (cert) {

  		public_key_free(cert->pub);

  		public_key_signature_free(cert->sig);

  		kfree(cert->issuer);
  		kfree(cert->subject);

  		kfree(cert->id);
  		kfree(cert->skid);

  		kfree(cert);
  	}
  }

  EXPORT_SYMBOL_GPL(x509_free_certificate);

  
  /*
   * Parse an X.509 certificate
   */
  struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  {
  	struct x509_certificate *cert;
  	struct x509_parse_context *ctx;

  	struct asymmetric_key_id *kid;

  	long ret;
  
  	ret = -ENOMEM;
  	cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  	if (!cert)
  		goto error_no_cert;
  	cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  	if (!cert->pub)
  		goto error_no_ctx;

  	cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
  	if (!cert->sig)
  		goto error_no_ctx;

  	ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  	if (!ctx)
  		goto error_no_ctx;
  
  	ctx->cert = cert;
  	ctx->data = (unsigned long)data;
  
  	/* Attempt to decode the certificate */
  	ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  	if (ret < 0)
  		goto error_decode;

  	/* Decode the AuthorityKeyIdentifier */
  	if (ctx->raw_akid) {
  		pr_devel("AKID: %u %*phN
  ",
  			 ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid);
  		ret = asn1_ber_decoder(&x509_akid_decoder, ctx,
  				       ctx->raw_akid, ctx->raw_akid_size);
  		if (ret < 0) {
  			pr_warn("Couldn't decode AuthKeyIdentifier
  ");
  			goto error_decode;
  		}
  	}

  	cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
  	if (!cert->pub->key)

  		goto error_decode;

  	cert->pub->keylen = ctx->key_size;

  	/* Grab the signature bits */
  	ret = x509_get_sig_params(cert);
  	if (ret < 0)
  		goto error_decode;

  	/* Generate cert issuer + serial number key ID */
  	kid = asymmetric_key_generate_id(cert->raw_serial,
  					 cert->raw_serial_size,
  					 cert->raw_issuer,
  					 cert->raw_issuer_size);
  	if (IS_ERR(kid)) {
  		ret = PTR_ERR(kid);
  		goto error_decode;
  	}
  	cert->id = kid;

  	/* Detect self-signed certificates */
  	ret = x509_check_for_self_signed(cert);
  	if (ret < 0)
  		goto error_decode;

  	kfree(ctx);
  	return cert;
  
  error_decode:

  	kfree(cert->pub->key);

  	kfree(ctx);
  error_no_ctx:
  	x509_free_certificate(cert);
  error_no_cert:
  	return ERR_PTR(ret);
  }

  EXPORT_SYMBOL_GPL(x509_cert_parse);

  
  /*
   * Note an OID when we find one for later processing when we know how
   * to interpret it.
   */
  int x509_note_OID(void *context, size_t hdrlen,
  	     unsigned char tag,
  	     const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	ctx->last_oid = look_up_OID(value, vlen);
  	if (ctx->last_oid == OID__NR) {
  		char buffer[50];
  		sprint_oid(value, vlen, buffer, sizeof(buffer));

  		pr_debug("Unknown OID: [%lu] %s
  ",

  			 (unsigned long)value - ctx->data, buffer);
  	}
  	return 0;
  }
  
  /*
   * Save the position of the TBS data so that we can check the signature over it
   * later.
   */
  int x509_note_tbs_certificate(void *context, size_t hdrlen,
  			      unsigned char tag,
  			      const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!
  ",
  		 hdrlen, tag, (unsigned long)value - ctx->data, vlen);
  
  	ctx->cert->tbs = value - hdrlen;
  	ctx->cert->tbs_size = vlen + hdrlen;
  	return 0;
  }
  
  /*
   * Record the public key algorithm
   */
  int x509_note_pkey_algo(void *context, size_t hdrlen,
  			unsigned char tag,
  			const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	pr_debug("PubKey Algo: %u
  ", ctx->last_oid);
  
  	switch (ctx->last_oid) {
  	case OID_md2WithRSAEncryption:
  	case OID_md3WithRSAEncryption:
  	default:
  		return -ENOPKG; /* Unsupported combination */
  
  	case OID_md4WithRSAEncryption:

  		ctx->cert->sig->hash_algo = "md4";
  		ctx->cert->sig->pkey_algo = "rsa";

  		break;
  
  	case OID_sha1WithRSAEncryption:

  		ctx->cert->sig->hash_algo = "sha1";
  		ctx->cert->sig->pkey_algo = "rsa";

  		break;
  
  	case OID_sha256WithRSAEncryption:

  		ctx->cert->sig->hash_algo = "sha256";
  		ctx->cert->sig->pkey_algo = "rsa";

  		break;
  
  	case OID_sha384WithRSAEncryption:

  		ctx->cert->sig->hash_algo = "sha384";
  		ctx->cert->sig->pkey_algo = "rsa";

  		break;
  
  	case OID_sha512WithRSAEncryption:

  		ctx->cert->sig->hash_algo = "sha512";
  		ctx->cert->sig->pkey_algo = "rsa";

  		break;
  
  	case OID_sha224WithRSAEncryption:

  		ctx->cert->sig->hash_algo = "sha224";
  		ctx->cert->sig->pkey_algo = "rsa";

  		break;
  	}
  
  	ctx->algo_oid = ctx->last_oid;
  	return 0;
  }
  
  /*
   * Note the whereabouts and type of the signature.
   */
  int x509_note_signature(void *context, size_t hdrlen,
  			unsigned char tag,
  			const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	pr_debug("Signature type: %u size %zu
  ", ctx->last_oid, vlen);
  
  	if (ctx->last_oid != ctx->algo_oid) {
  		pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs
  ",
  			ctx->algo_oid, ctx->last_oid);
  		return -EINVAL;
  	}

  	ctx->cert->raw_sig = value;
  	ctx->cert->raw_sig_size = vlen;

  	return 0;
  }
  
  /*

   * Note the certificate serial number
   */
  int x509_note_serial(void *context, size_t hdrlen,
  		     unsigned char tag,
  		     const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  	ctx->cert->raw_serial = value;
  	ctx->cert->raw_serial_size = vlen;
  	return 0;
  }
  
  /*

   * Note some of the name segments from which we'll fabricate a name.
   */
  int x509_extract_name_segment(void *context, size_t hdrlen,
  			      unsigned char tag,
  			      const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	switch (ctx->last_oid) {
  	case OID_commonName:
  		ctx->cn_size = vlen;
  		ctx->cn_offset = (unsigned long)value - ctx->data;
  		break;
  	case OID_organizationName:
  		ctx->o_size = vlen;
  		ctx->o_offset = (unsigned long)value - ctx->data;
  		break;
  	case OID_email_address:
  		ctx->email_size = vlen;
  		ctx->email_offset = (unsigned long)value - ctx->data;
  		break;
  	default:
  		break;
  	}
  
  	return 0;
  }
  
  /*
   * Fabricate and save the issuer and subject names
   */
  static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
  			       unsigned char tag,
  			       char **_name, size_t vlen)
  {
  	const void *name, *data = (const void *)ctx->data;
  	size_t namesize;
  	char *buffer;
  
  	if (*_name)
  		return -EINVAL;
  
  	/* Empty name string if no material */
  	if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
  		buffer = kmalloc(1, GFP_KERNEL);
  		if (!buffer)
  			return -ENOMEM;
  		buffer[0] = 0;
  		goto done;
  	}
  
  	if (ctx->cn_size && ctx->o_size) {
  		/* Consider combining O and CN, but use only the CN if it is
  		 * prefixed by the O, or a significant portion thereof.
  		 */
  		namesize = ctx->cn_size;
  		name = data + ctx->cn_offset;
  		if (ctx->cn_size >= ctx->o_size &&
  		    memcmp(data + ctx->cn_offset, data + ctx->o_offset,
  			   ctx->o_size) == 0)
  			goto single_component;
  		if (ctx->cn_size >= 7 &&
  		    ctx->o_size >= 7 &&
  		    memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
  			goto single_component;
  
  		buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
  				 GFP_KERNEL);
  		if (!buffer)
  			return -ENOMEM;
  
  		memcpy(buffer,
  		       data + ctx->o_offset, ctx->o_size);
  		buffer[ctx->o_size + 0] = ':';
  		buffer[ctx->o_size + 1] = ' ';
  		memcpy(buffer + ctx->o_size + 2,
  		       data + ctx->cn_offset, ctx->cn_size);
  		buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
  		goto done;
  
  	} else if (ctx->cn_size) {
  		namesize = ctx->cn_size;
  		name = data + ctx->cn_offset;
  	} else if (ctx->o_size) {
  		namesize = ctx->o_size;
  		name = data + ctx->o_offset;
  	} else {
  		namesize = ctx->email_size;
  		name = data + ctx->email_offset;
  	}
  
  single_component:
  	buffer = kmalloc(namesize + 1, GFP_KERNEL);
  	if (!buffer)
  		return -ENOMEM;
  	memcpy(buffer, name, namesize);
  	buffer[namesize] = 0;
  
  done:
  	*_name = buffer;
  	ctx->cn_size = 0;
  	ctx->o_size = 0;
  	ctx->email_size = 0;
  	return 0;
  }
  
  int x509_note_issuer(void *context, size_t hdrlen,
  		     unsigned char tag,
  		     const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;

  	ctx->cert->raw_issuer = value;
  	ctx->cert->raw_issuer_size = vlen;

  	return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
  }
  
  int x509_note_subject(void *context, size_t hdrlen,
  		      unsigned char tag,
  		      const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;

  	ctx->cert->raw_subject = value;
  	ctx->cert->raw_subject_size = vlen;

  	return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
  }
  
  /*
   * Extract the data for the public key algorithm
   */
  int x509_extract_key_data(void *context, size_t hdrlen,
  			  unsigned char tag,
  			  const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	if (ctx->last_oid != OID_rsaEncryption)
  		return -ENOPKG;

  	ctx->cert->pub->pkey_algo = "rsa";

  
  	/* Discard the BIT STRING metadata */

  	ctx->key = value + 1;
  	ctx->key_size = vlen - 1;
  	return 0;
  }

  /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
  #define SEQ_TAG_KEYID (ASN1_CONT << 6)

  /*
   * Process certificate extensions that are used to qualify the certificate.
   */
  int x509_process_extension(void *context, size_t hdrlen,
  			   unsigned char tag,
  			   const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;

  	struct asymmetric_key_id *kid;

  	const unsigned char *v = value;

  
  	pr_debug("Extension: %u
  ", ctx->last_oid);
  
  	if (ctx->last_oid == OID_subjectKeyIdentifier) {
  		/* Get hold of the key fingerprint */

  		if (ctx->cert->skid || vlen < 3)

  			return -EBADMSG;
  		if (v[0] != ASN1_OTS || v[1] != vlen - 2)
  			return -EBADMSG;
  		v += 2;
  		vlen -= 2;

  		ctx->cert->raw_skid_size = vlen;
  		ctx->cert->raw_skid = v;

  		kid = asymmetric_key_generate_id(v, vlen, "", 0);

  		if (IS_ERR(kid))
  			return PTR_ERR(kid);
  		ctx->cert->skid = kid;
  		pr_debug("subjkeyid %*phN
  ", kid->len, kid->data);

  		return 0;
  	}
  
  	if (ctx->last_oid == OID_authorityKeyIdentifier) {
  		/* Get hold of the CA key fingerprint */

  		ctx->raw_akid = v;
  		ctx->raw_akid_size = vlen;

  		return 0;
  	}
  
  	return 0;
  }

  /**
   * x509_decode_time - Decode an X.509 time ASN.1 object
   * @_t: The time to fill in
   * @hdrlen: The length of the object header
   * @tag: The object tag
   * @value: The object value
   * @vlen: The size of the object value
   *
   * Decode an ASN.1 universal time or generalised time field into a struct the
   * kernel can handle and check it for validity.  The time is decoded thus:
   *
   *	[RFC5280 §4.1.2.5]
   *	CAs conforming to this profile MUST always encode certificate validity
   *	dates through the year 2049 as UTCTime; certificate validity dates in
   *	2050 or later MUST be encoded as GeneralizedTime.  Conforming
   *	applications MUST be able to process validity dates that are encoded in
   *	either UTCTime or GeneralizedTime.

   */

  int x509_decode_time(time64_t *_t,  size_t hdrlen,
  		     unsigned char tag,
  		     const unsigned char *value, size_t vlen)

  {

  	static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,

  						       31, 31, 30, 31, 30, 31 };

  	const unsigned char *p = value;

  	unsigned year, mon, day, hour, min, sec, mon_len;

  #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })

  #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
  
  	if (tag == ASN1_UNITIM) {
  		/* UTCTime: YYMMDDHHMMSSZ */
  		if (vlen != 13)
  			goto unsupported_time;

  		year = DD2bin(p);
  		if (year >= 50)
  			year += 1900;

  		else

  			year += 2000;

  	} else if (tag == ASN1_GENTIM) {
  		/* GenTime: YYYYMMDDHHMMSSZ */
  		if (vlen != 15)
  			goto unsupported_time;

  		year = DD2bin(p) * 100 + DD2bin(p);
  		if (year >= 1950 && year <= 2049)
  			goto invalid_time;

  	} else {
  		goto unsupported_time;
  	}

  	mon  = DD2bin(p);
  	day = DD2bin(p);
  	hour = DD2bin(p);
  	min  = DD2bin(p);
  	sec  = DD2bin(p);

  
  	if (*p != 'Z')
  		goto unsupported_time;

  	if (year < 1970 ||
  	    mon < 1 || mon > 12)
  		goto invalid_time;
  
  	mon_len = month_lengths[mon - 1];

  	if (mon == 2) {
  		if (year % 4 == 0) {
  			mon_len = 29;
  			if (year % 100 == 0) {

  				mon_len = 28;
  				if (year % 400 == 0)
  					mon_len = 29;

  			}
  		}
  	}

  	if (day < 1 || day > mon_len ||

  	    hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */

  	    min > 59 ||

  	    sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */

  		goto invalid_time;

  	*_t = mktime64(year, mon, day, hour, min, sec);

  	return 0;
  
  unsupported_time:

  	pr_debug("Got unsupported time [tag %02x]: '%*phN'
  ",
  		 tag, (int)vlen, value);
  	return -EBADMSG;
  invalid_time:
  	pr_debug("Got invalid time [tag %02x]: '%*phN'
  ",
  		 tag, (int)vlen, value);

  	return -EBADMSG;
  }

  EXPORT_SYMBOL_GPL(x509_decode_time);

  
  int x509_note_not_before(void *context, size_t hdrlen,
  			 unsigned char tag,
  			 const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;

  	return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);

  }
  
  int x509_note_not_after(void *context, size_t hdrlen,
  			unsigned char tag,
  			const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;

  	return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);

  }

  
  /*
   * Note a key identifier-based AuthorityKeyIdentifier
   */
  int x509_akid_note_kid(void *context, size_t hdrlen,
  		       unsigned char tag,
  		       const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  	struct asymmetric_key_id *kid;
  
  	pr_debug("AKID: keyid: %*phN
  ", (int)vlen, value);

  	if (ctx->cert->sig->auth_ids[1])

  		return 0;

  	kid = asymmetric_key_generate_id(value, vlen, "", 0);

  	if (IS_ERR(kid))
  		return PTR_ERR(kid);
  	pr_debug("authkeyid %*phN
  ", kid->len, kid->data);

  	ctx->cert->sig->auth_ids[1] = kid;

  	return 0;
  }
  
  /*
   * Note a directoryName in an AuthorityKeyIdentifier
   */
  int x509_akid_note_name(void *context, size_t hdrlen,
  			unsigned char tag,
  			const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  
  	pr_debug("AKID: name: %*phN
  ", (int)vlen, value);
  
  	ctx->akid_raw_issuer = value;
  	ctx->akid_raw_issuer_size = vlen;
  	return 0;
  }
  
  /*
   * Note a serial number in an AuthorityKeyIdentifier
   */
  int x509_akid_note_serial(void *context, size_t hdrlen,
  			  unsigned char tag,
  			  const void *value, size_t vlen)
  {
  	struct x509_parse_context *ctx = context;
  	struct asymmetric_key_id *kid;
  
  	pr_debug("AKID: serial: %*phN
  ", (int)vlen, value);

  	if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])

  		return 0;
  
  	kid = asymmetric_key_generate_id(value,
  					 vlen,
  					 ctx->akid_raw_issuer,
  					 ctx->akid_raw_issuer_size);
  	if (IS_ERR(kid))
  		return PTR_ERR(kid);
  
  	pr_debug("authkeyid %*phN
  ", kid->len, kid->data);

  	ctx->cert->sig->auth_ids[0] = kid;

  	return 0;
  }