/* PKCS#7 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) "PKCS7: "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 "pkcs7_parser.h"
#include "pkcs7-asn1.h"

struct pkcs7_parse_context {
        struct pkcs7_message    *msg;           /* Message being constructed */
        struct pkcs7_signed_info *sinfo;        /* SignedInfo being constructed */
        struct pkcs7_signed_info **ppsinfo;
        struct x509_certificate *certs;         /* Certificate cache */
        struct x509_certificate **ppcerts;
        unsigned long   data;                   /* Start of data */
        enum OID        last_oid;               /* Last OID encountered */
        unsigned        x509_index;
        unsigned        sinfo_index;
        const void      *raw_serial;
        unsigned        raw_serial_size;
        unsigned        raw_issuer_size;
        const void      *raw_issuer;
        const void      *raw_skid;
        unsigned        raw_skid_size;
        bool            expect_skid;
};

/*
 * Free a signed information block.
 */
static void pkcs7_free_signed_info(struct pkcs7_signed_info *sinfo)
{
        if (sinfo) {
                public_key_signature_free(sinfo->sig);
                kfree(sinfo);
        }
}

/**
 * pkcs7_free_message - Free a PKCS#7 message
 * @pkcs7: The PKCS#7 message to free
 */
void pkcs7_free_message(struct pkcs7_message *pkcs7)
{
        struct x509_certificate *cert;
        struct pkcs7_signed_info *sinfo;

        if (pkcs7) {
                while (pkcs7->certs) {
                        cert = pkcs7->certs;
                        pkcs7->certs = cert->next;
                        x509_free_certificate(cert);
                }
                while (pkcs7->crl) {
                        cert = pkcs7->crl;
                        pkcs7->crl = cert->next;
                        x509_free_certificate(cert);
                }
                while (pkcs7->signed_infos) {
                        sinfo = pkcs7->signed_infos;
                        pkcs7->signed_infos = sinfo->next;
                        pkcs7_free_signed_info(sinfo);
                }
                kfree(pkcs7);
        }
}
EXPORT_SYMBOL_GPL(pkcs7_free_message);

/*
 * Check authenticatedAttributes are provided or not provided consistently.
 */
static int pkcs7_check_authattrs(struct pkcs7_message *msg)
{
        struct pkcs7_signed_info *sinfo;
        bool want = false;

        sinfo = msg->signed_infos;
        if (!sinfo)
                goto inconsistent;

        if (sinfo->authattrs) {
                want = true;
                msg->have_authattrs = true;
        }

        for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
                if (!!sinfo->authattrs != want)
                        goto inconsistent;
        return 0;

inconsistent:
        pr_warn("Inconsistently supplied authAttrs\n");
        return -EINVAL;
}

/**
 * pkcs7_parse_message - Parse a PKCS#7 message
 * @data: The raw binary ASN.1 encoded message to be parsed
 * @datalen: The size of the encoded message
 */
struct pkcs7_message *pkcs7_parse_message(const void *data, size_t datalen)
{
        struct pkcs7_parse_context *ctx;
        struct pkcs7_message *msg = ERR_PTR(-ENOMEM);
        int ret;

        ctx = kzalloc(sizeof(struct pkcs7_parse_context), GFP_KERNEL);
        if (!ctx)
                goto out_no_ctx;
        ctx->msg = kzalloc(sizeof(struct pkcs7_message), GFP_KERNEL);
        if (!ctx->msg)
                goto out_no_msg;
        ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
        if (!ctx->sinfo)
                goto out_no_sinfo;
        ctx->sinfo->sig = kzalloc(sizeof(struct public_key_signature),
                                  GFP_KERNEL);
        if (!ctx->sinfo->sig)
                goto out_no_sig;

        ctx->data = (unsigned long)data;
        ctx->ppcerts = &ctx->certs;
        ctx->ppsinfo = &ctx->msg->signed_infos;

        /* Attempt to decode the signature */
        ret = asn1_ber_decoder(&pkcs7_decoder, ctx, data, datalen);
        if (ret < 0) {
                msg = ERR_PTR(ret);
                goto out;
        }

        ret = pkcs7_check_authattrs(ctx->msg);
        if (ret < 0)
                goto out;

        msg = ctx->msg;
        ctx->msg = NULL;

out:
        while (ctx->certs) {
                struct x509_certificate *cert = ctx->certs;
                ctx->certs = cert->next;
                x509_free_certificate(cert);
        }
out_no_sig:
        pkcs7_free_signed_info(ctx->sinfo);
out_no_sinfo:
        pkcs7_free_message(ctx->msg);
out_no_msg:
        kfree(ctx);
out_no_ctx:
        return msg;
}
EXPORT_SYMBOL_GPL(pkcs7_parse_message);

/**
 * pkcs7_get_content_data - Get access to the PKCS#7 content
 * @pkcs7: The preparsed PKCS#7 message to access
 * @_data: Place to return a pointer to the data
 * @_data_len: Place to return the data length
 * @_headerlen: Size of ASN.1 header not included in _data
 *
 * Get access to the data content of the PKCS#7 message.  The size of the
 * header of the ASN.1 object that contains it is also provided and can be used
 * to adjust *_data and *_data_len to get the entire object.
 *
 * Returns -ENODATA if the data object was missing from the message.
 */
int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
                           const void **_data, size_t *_data_len,
                           size_t *_headerlen)
{
        if (!pkcs7->data)
                return -ENODATA;

        *_data = pkcs7->data;
        *_data_len = pkcs7->data_len;
        if (_headerlen)
                *_headerlen = pkcs7->data_hdrlen;
        return 0;
}
EXPORT_SYMBOL_GPL(pkcs7_get_content_data);

/*
 * Note an OID when we find one for later processing when we know how
 * to interpret it.
 */
int pkcs7_note_OID(void *context, size_t hdrlen,
                   unsigned char tag,
                   const void *value, size_t vlen)
{
        struct pkcs7_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));
                printk("PKCS7: Unknown OID: [%lu] %s\n",
                       (unsigned long)value - ctx->data, buffer);
        }
        return 0;
}

/*
 * Note the digest algorithm for the signature.
 */
int pkcs7_sig_note_digest_algo(void *context, size_t hdrlen,
                               unsigned char tag,
                               const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        switch (ctx->last_oid) {
        case OID_md4:
                ctx->sinfo->sig->hash_algo = "md4";
                break;
        case OID_md5:
                ctx->sinfo->sig->hash_algo = "md5";
                break;
        case OID_sha1:
                ctx->sinfo->sig->hash_algo = "sha1";
                break;
        case OID_sha256:
                ctx->sinfo->sig->hash_algo = "sha256";
                break;
        case OID_sha384:
                ctx->sinfo->sig->hash_algo = "sha384";
                break;
        case OID_sha512:
                ctx->sinfo->sig->hash_algo = "sha512";
                break;
        case OID_sha224:
                ctx->sinfo->sig->hash_algo = "sha224";
                break;
        default:
                printk("Unsupported digest algo: %u\n", ctx->last_oid);
                return -ENOPKG;
        }
        return 0;
}

/*
 * Note the public key algorithm for the signature.
 */
int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
                             unsigned char tag,
                             const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        switch (ctx->last_oid) {
        case OID_rsaEncryption:
                ctx->sinfo->sig->pkey_algo = "rsa";
                break;
        default:
                printk("Unsupported pkey algo: %u\n", ctx->last_oid);
                return -ENOPKG;
        }
        return 0;
}

/*
 * We only support signed data [RFC2315 sec 9].
 */
int pkcs7_check_content_type(void *context, size_t hdrlen,
                             unsigned char tag,
                             const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        if (ctx->last_oid != OID_signed_data) {
                pr_warn("Only support pkcs7_signedData type\n");
                return -EINVAL;
        }

        return 0;
}

/*
 * Note the SignedData version
 */
int pkcs7_note_signeddata_version(void *context, size_t hdrlen,
                                  unsigned char tag,
                                  const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        unsigned version;

        if (vlen != 1)
                goto unsupported;

        ctx->msg->version = version = *(const u8 *)value;
        switch (version) {
        case 1:
                /* PKCS#7 SignedData [RFC2315 sec 9.1]
                 * CMS ver 1 SignedData [RFC5652 sec 5.1]
                 */
                break;
        case 3:
                /* CMS ver 3 SignedData [RFC2315 sec 5.1] */
                break;
        default:
                goto unsupported;
        }

        return 0;

unsupported:
        pr_warn("Unsupported SignedData version\n");
        return -EINVAL;
}

/*
 * Note the SignerInfo version
 */
int pkcs7_note_signerinfo_version(void *context, size_t hdrlen,
                                  unsigned char tag,
                                  const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        unsigned version;

        if (vlen != 1)
                goto unsupported;

        version = *(const u8 *)value;
        switch (version) {
        case 1:
                /* PKCS#7 SignerInfo [RFC2315 sec 9.2]
                 * CMS ver 1 SignerInfo [RFC5652 sec 5.3]
                 */
                if (ctx->msg->version != 1)
                        goto version_mismatch;
                ctx->expect_skid = false;
                break;
        case 3:
                /* CMS ver 3 SignerInfo [RFC2315 sec 5.3] */
                if (ctx->msg->version == 1)
                        goto version_mismatch;
                ctx->expect_skid = true;
                break;
        default:
                goto unsupported;
        }

        return 0;

unsupported:
        pr_warn("Unsupported SignerInfo version\n");
        return -EINVAL;
version_mismatch:
        pr_warn("SignedData-SignerInfo version mismatch\n");
        return -EBADMSG;
}

/*
 * Extract a certificate and store it in the context.
 */
int pkcs7_extract_cert(void *context, size_t hdrlen,
                       unsigned char tag,
                       const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        struct x509_certificate *x509;

        if (tag != ((ASN1_UNIV << 6) | ASN1_CONS_BIT | ASN1_SEQ)) {
                pr_debug("Cert began with tag %02x at %lu\n",
                         tag, (unsigned long)ctx - ctx->data);
                return -EBADMSG;
        }

        /* We have to correct for the header so that the X.509 parser can start
         * from the beginning.  Note that since X.509 stipulates DER, there
         * probably shouldn't be an EOC trailer - but it is in PKCS#7 (which
         * stipulates BER).
         */
        value -= hdrlen;
        vlen += hdrlen;

        if (((u8*)value)[1] == 0x80)
                vlen += 2; /* Indefinite length - there should be an EOC */

        x509 = x509_cert_parse(value, vlen);
        if (IS_ERR(x509))
                return PTR_ERR(x509);

        x509->index = ++ctx->x509_index;
        pr_debug("Got cert %u for %s\n", x509->index, x509->subject);
        pr_debug("- fingerprint %*phN\n", x509->id->len, x509->id->data);

        *ctx->ppcerts = x509;
        ctx->ppcerts = &x509->next;
        return 0;
}

/*
 * Save the certificate list
 */
int pkcs7_note_certificate_list(void *context, size_t hdrlen,
                                unsigned char tag,
                                const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        pr_devel("Got cert list (%02x)\n", tag);

        *ctx->ppcerts = ctx->msg->certs;
        ctx->msg->certs = ctx->certs;
        ctx->certs = NULL;
        ctx->ppcerts = &ctx->certs;
        return 0;
}

/*
 * Note the content type.
 */
int pkcs7_note_content(void *context, size_t hdrlen,
                       unsigned char tag,
                       const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        if (ctx->last_oid != OID_data &&
            ctx->last_oid != OID_msIndirectData) {
                pr_warn("Unsupported data type %d\n", ctx->last_oid);
                return -EINVAL;
        }

        ctx->msg->data_type = ctx->last_oid;
        return 0;
}

/*
 * Extract the data from the message and store that and its content type OID in
 * the context.
 */
int pkcs7_note_data(void *context, size_t hdrlen,
                    unsigned char tag,
                    const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        pr_debug("Got data\n");

        ctx->msg->data = value;
        ctx->msg->data_len = vlen;
        ctx->msg->data_hdrlen = hdrlen;
        return 0;
}

/*
 * Parse authenticated attributes.
 */
int pkcs7_sig_note_authenticated_attr(void *context, size_t hdrlen,
                                      unsigned char tag,
                                      const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        struct pkcs7_signed_info *sinfo = ctx->sinfo;
        enum OID content_type;

        pr_devel("AuthAttr: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);

        switch (ctx->last_oid) {
        case OID_contentType:
                if (__test_and_set_bit(sinfo_has_content_type, &sinfo->aa_set))
                        goto repeated;
                content_type = look_up_OID(value, vlen);
                if (content_type != ctx->msg->data_type) {
                        pr_warn("Mismatch between global data type (%d) and sinfo %u (%d)\n",
                                ctx->msg->data_type, sinfo->index,
                                content_type);
                        return -EBADMSG;
                }
                return 0;

        case OID_signingTime:
                if (__test_and_set_bit(sinfo_has_signing_time, &sinfo->aa_set))
                        goto repeated;
                /* Should we check that the signing time is consistent
                 * with the signer's X.509 cert?
                 */
                return x509_decode_time(&sinfo->signing_time,
                                        hdrlen, tag, value, vlen);

        case OID_messageDigest:
                if (__test_and_set_bit(sinfo_has_message_digest, &sinfo->aa_set))
                        goto repeated;
                if (tag != ASN1_OTS)
                        return -EBADMSG;
                sinfo->msgdigest = value;
                sinfo->msgdigest_len = vlen;
                return 0;

        case OID_smimeCapabilites:
                if (__test_and_set_bit(sinfo_has_smime_caps, &sinfo->aa_set))
                        goto repeated;
                if (ctx->msg->data_type != OID_msIndirectData) {
                        pr_warn("S/MIME Caps only allowed with Authenticode\n");
                        return -EKEYREJECTED;
                }
                return 0;

                /* Microsoft SpOpusInfo seems to be contain cont[0] 16-bit BE
                 * char URLs and cont[1] 8-bit char URLs.
                 *
                 * Microsoft StatementType seems to contain a list of OIDs that
                 * are also used as extendedKeyUsage types in X.509 certs.
                 */
        case OID_msSpOpusInfo:
                if (__test_and_set_bit(sinfo_has_ms_opus_info, &sinfo->aa_set))
                        goto repeated;
                goto authenticode_check;
        case OID_msStatementType:
                if (__test_and_set_bit(sinfo_has_ms_statement_type, &sinfo->aa_set))
                        goto repeated;
        authenticode_check:
                if (ctx->msg->data_type != OID_msIndirectData) {
                        pr_warn("Authenticode AuthAttrs only allowed with Authenticode\n");
                        return -EKEYREJECTED;
                }
                /* I'm not sure how to validate these */
                return 0;
        default:
                return 0;
        }

repeated:
        /* We permit max one item per AuthenticatedAttribute and no repeats */
        pr_warn("Repeated/multivalue AuthAttrs not permitted\n");
        return -EKEYREJECTED;
}

/*
 * Note the set of auth attributes for digestion purposes [RFC2315 sec 9.3]
 */
int pkcs7_sig_note_set_of_authattrs(void *context, size_t hdrlen,
                                    unsigned char tag,
                                    const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        struct pkcs7_signed_info *sinfo = ctx->sinfo;

        if (!test_bit(sinfo_has_content_type, &sinfo->aa_set) ||
            !test_bit(sinfo_has_message_digest, &sinfo->aa_set)) {
                pr_warn("Missing required AuthAttr\n");
                return -EBADMSG;
        }

        if (ctx->msg->data_type != OID_msIndirectData &&
            test_bit(sinfo_has_ms_opus_info, &sinfo->aa_set)) {
                pr_warn("Unexpected Authenticode AuthAttr\n");
                return -EBADMSG;
        }

        /* We need to switch the 'CONT 0' to a 'SET OF' when we digest */
        sinfo->authattrs = value - (hdrlen - 1);
        sinfo->authattrs_len = vlen + (hdrlen - 1);
        return 0;
}

/*
 * Note the issuing certificate serial number
 */
int pkcs7_sig_note_serial(void *context, size_t hdrlen,
                          unsigned char tag,
                          const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        ctx->raw_serial = value;
        ctx->raw_serial_size = vlen;
        return 0;
}

/*
 * Note the issuer's name
 */
int pkcs7_sig_note_issuer(void *context, size_t hdrlen,
                          unsigned char tag,
                          const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        ctx->raw_issuer = value;
        ctx->raw_issuer_size = vlen;
        return 0;
}

/*
 * Note the issuing cert's subjectKeyIdentifier
 */
int pkcs7_sig_note_skid(void *context, size_t hdrlen,
                        unsigned char tag,
                        const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        pr_devel("SKID: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);

        ctx->raw_skid = value;
        ctx->raw_skid_size = vlen;
        return 0;
}

/*
 * Note the signature data
 */
int pkcs7_sig_note_signature(void *context, size_t hdrlen,
                             unsigned char tag,
                             const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;

        ctx->sinfo->sig->s = kmemdup(value, vlen, GFP_KERNEL);
        if (!ctx->sinfo->sig->s)
                return -ENOMEM;

        ctx->sinfo->sig->s_size = vlen;
        return 0;
}

/*
 * Note a signature information block
 */
int pkcs7_note_signed_info(void *context, size_t hdrlen,
                           unsigned char tag,
                           const void *value, size_t vlen)
{
        struct pkcs7_parse_context *ctx = context;
        struct pkcs7_signed_info *sinfo = ctx->sinfo;
        struct asymmetric_key_id *kid;

        if (ctx->msg->data_type == OID_msIndirectData && !sinfo->authattrs) {
                pr_warn("Authenticode requires AuthAttrs\n");
                return -EBADMSG;
        }

        /* Generate cert issuer + serial number key ID */
        if (!ctx->expect_skid) {
                kid = asymmetric_key_generate_id(ctx->raw_serial,
                                                 ctx->raw_serial_size,
                                                 ctx->raw_issuer,
                                                 ctx->raw_issuer_size);
        } else {
                kid = asymmetric_key_generate_id(ctx->raw_skid,
                                                 ctx->raw_skid_size,
                                                 "", 0);
        }
        if (IS_ERR(kid))
                return PTR_ERR(kid);

        pr_devel("SINFO KID: %u [%*phN]\n", kid->len, kid->len, kid->data);

        sinfo->sig->auth_ids[0] = kid;
        sinfo->index = ++ctx->sinfo_index;
        *ctx->ppsinfo = sinfo;
        ctx->ppsinfo = &sinfo->next;
        ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
        if (!ctx->sinfo)
                return -ENOMEM;
        ctx->sinfo->sig = kzalloc(sizeof(struct public_key_signature),
                                  GFP_KERNEL);
        if (!ctx->sinfo->sig)
                return -ENOMEM;
        return 0;
}