PKCS#7: Implement a parser [RFC 2315]

Implement a parser for a PKCS#7 signed-data message as described in part of
RFC 2315.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>

5 files changed, 606 insertions, 0 deletions

diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index 03a6eb95ab50..a7cec9dd6154 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -37,4 +37,13 @@ config X509_CERTIFICATE_PARSER
           data and provides the ability to instantiate a crypto key from a
           public key packet found inside the certificate.
 
+config PKCS7_MESSAGE_PARSER
+        tristate "PKCS#7 message parser"
+        depends on X509_CERTIFICATE_PARSER
+        select ASN1
+        select OID_REGISTRY
+        help
+          This option provides support for parsing PKCS#7 format messages for
+          signature data and provides the ability to verify the signature.
+
 endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index 0727204aab68..59d8cade5cfe 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -25,3 +25,16 @@ $(obj)/x509_rsakey-asn1.o: $(obj)/x509_rsakey-asn1.c $(obj)/x509_rsakey-asn1.h
 
 clean-files     += x509-asn1.c x509-asn1.h
 clean-files     += x509_rsakey-asn1.c x509_rsakey-asn1.h
+
+#
+# PKCS#7 message handling
+#
+obj-$(CONFIG_PKCS7_MESSAGE_PARSER) += pkcs7_message.o
+pkcs7_message-y := \
+        pkcs7-asn1.o \
+        pkcs7_parser.o
+
+$(obj)/pkcs7_parser.o: $(obj)/pkcs7-asn1.h
+$(obj)/pkcs7-asn1.o: $(obj)/pkcs7-asn1.c $(obj)/pkcs7-asn1.h
+
+clean-files     += pkcs7-asn1.c pkcs7-asn1.h
diff --git a/crypto/asymmetric_keys/pkcs7.asn1 b/crypto/asymmetric_keys/pkcs7.asn1
new file mode 100644
index 000000000000..a5a14ef28c86
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs7.asn1
@@ -0,0 +1,127 @@
+PKCS7ContentInfo ::= SEQUENCE {
+        contentType     ContentType,
+        content         [0] EXPLICIT SignedData OPTIONAL
+}
+
+ContentType ::= OBJECT IDENTIFIER ({ pkcs7_note_OID })
+
+SignedData ::= SEQUENCE {
+        version                 INTEGER,
+        digestAlgorithms        DigestAlgorithmIdentifiers,
+        contentInfo             ContentInfo,
+        certificates            CHOICE {
+                certSet         [0] IMPLICIT ExtendedCertificatesAndCertificates,
+                certSequence    [2] IMPLICIT Certificates
+        } OPTIONAL ({ pkcs7_note_certificate_list }),
+        crls CHOICE {
+                crlSet          [1] IMPLICIT CertificateRevocationLists,
+                crlSequence     [3] IMPLICIT CRLSequence
+        } OPTIONAL,
+        signerInfos             SignerInfos
+}
+
+ContentInfo ::= SEQUENCE {
+        contentType     ContentType,
+        content         [0] EXPLICIT Data OPTIONAL
+}
+
+Data ::= ANY ({ pkcs7_note_data })
+
+DigestAlgorithmIdentifiers ::= CHOICE {
+        daSet                   SET OF DigestAlgorithmIdentifier,
+        daSequence              SEQUENCE OF DigestAlgorithmIdentifier
+}
+
+DigestAlgorithmIdentifier ::= SEQUENCE {
+        algorithm   OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+        parameters  ANY OPTIONAL
+}
+
+--
+-- Certificates and certificate lists
+--
+ExtendedCertificatesAndCertificates ::= SET OF ExtendedCertificateOrCertificate
+
+ExtendedCertificateOrCertificate ::= CHOICE {
+  certificate           Certificate,                            -- X.509
+  extendedCertificate   [0] IMPLICIT ExtendedCertificate        -- PKCS#6
+}
+
+ExtendedCertificate ::= Certificate -- cheating
+
+Certificates ::= SEQUENCE OF Certificate
+
+CertificateRevocationLists ::= SET OF CertificateList
+
+CertificateList ::= SEQUENCE OF Certificate -- This may be defined incorrectly
+
+CRLSequence ::= SEQUENCE OF CertificateList
+
+Certificate ::= ANY ({ pkcs7_extract_cert }) -- X.509
+
+--
+-- Signer information
+--
+SignerInfos ::= CHOICE {
+        siSet           SET OF SignerInfo,
+        siSequence      SEQUENCE OF SignerInfo
+}
+
+SignerInfo ::= SEQUENCE {
+        version                 INTEGER,
+        issuerAndSerialNumber   IssuerAndSerialNumber,
+        digestAlgorithm         DigestAlgorithmIdentifier ({ pkcs7_sig_note_digest_algo }),
+        authenticatedAttributes CHOICE {
+                aaSet           [0] IMPLICIT SetOfAuthenticatedAttribute
+                                        ({ pkcs7_sig_note_set_of_authattrs }),
+                aaSequence      [2] EXPLICIT SEQUENCE OF AuthenticatedAttribute
+                        -- Explicit because easier to compute digest on
+                        -- sequence of attributes and then reuse encoded
+                        -- sequence in aaSequence.
+        } OPTIONAL,
+        digestEncryptionAlgorithm
+                                DigestEncryptionAlgorithmIdentifier ({ pkcs7_sig_note_pkey_algo }),
+        encryptedDigest         EncryptedDigest,
+        unauthenticatedAttributes CHOICE {
+                uaSet           [1] IMPLICIT SET OF UnauthenticatedAttribute,
+                uaSequence      [3] IMPLICIT SEQUENCE OF UnauthenticatedAttribute
+        } OPTIONAL
+} ({ pkcs7_note_signed_info })
+
+IssuerAndSerialNumber ::= SEQUENCE {
+        issuer                  Name ({ pkcs7_sig_note_issuer }),
+        serialNumber            CertificateSerialNumber ({ pkcs7_sig_note_serial })
+}
+
+CertificateSerialNumber ::= INTEGER
+
+SetOfAuthenticatedAttribute ::= SET OF AuthenticatedAttribute
+
+AuthenticatedAttribute ::= SEQUENCE {
+        type                    OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+        values                  SET OF ANY ({ pkcs7_sig_note_authenticated_attr })
+}
+
+UnauthenticatedAttribute ::= SEQUENCE {
+        type                    OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+        values                  SET OF ANY
+}
+
+DigestEncryptionAlgorithmIdentifier ::= SEQUENCE {
+        algorithm               OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+        parameters              ANY OPTIONAL
+}
+
+EncryptedDigest ::= OCTET STRING ({ pkcs7_sig_note_signature })
+
+---
+--- X.500 Name
+---
+Name ::= SEQUENCE OF RelativeDistinguishedName
+
+RelativeDistinguishedName ::= SET OF AttributeValueAssertion
+
+AttributeValueAssertion ::= SEQUENCE {
+        attributeType           OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+        attributeValue          ANY
+}
diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
new file mode 100644
index 000000000000..42e56aa7d277
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs7_parser.c
@@ -0,0 +1,396 @@
+/* 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 "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;
+};
+
+/**
+ * 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;
+                        mpi_free(sinfo->sig.mpi[0]);
+                        kfree(sinfo->sig.digest);
+                        kfree(sinfo);
+                }
+                kfree(pkcs7);
+        }
+}
+EXPORT_SYMBOL_GPL(pkcs7_free_message);
+
+/**
+ * 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;
+        long ret;
+
+        ret = -ENOMEM;
+        msg = kzalloc(sizeof(struct pkcs7_message), GFP_KERNEL);
+        if (!msg)
+                goto error_no_sig;
+        ctx = kzalloc(sizeof(struct pkcs7_parse_context), GFP_KERNEL);
+        if (!ctx)
+                goto error_no_ctx;
+        ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
+        if (!ctx->sinfo)
+                goto error_no_sinfo;
+
+        ctx->msg = msg;
+        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)
+                goto error_decode;
+
+        while (ctx->certs) {
+                struct x509_certificate *cert = ctx->certs;
+                ctx->certs = cert->next;
+                x509_free_certificate(cert);
+        }
+        mpi_free(ctx->sinfo->sig.mpi[0]);
+        kfree(ctx->sinfo->sig.digest);
+        kfree(ctx->sinfo);
+        kfree(ctx);
+        return msg;
+
+error_decode:
+        mpi_free(ctx->sinfo->sig.mpi[0]);
+        kfree(ctx->sinfo->sig.digest);
+        kfree(ctx->sinfo);
+error_no_sinfo:
+        kfree(ctx);
+error_no_ctx:
+        pkcs7_free_message(msg);
+error_no_sig:
+        return ERR_PTR(ret);
+}
+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
+ * @want_wrapper: True if the ASN.1 object header should be included in the data
+ *
+ * Get access to the data content of the PKCS#7 message, including, optionally,
+ * the header of the ASN.1 object that contains it.  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,
+                           bool want_wrapper)
+{
+        size_t wrapper;
+
+        if (!pkcs7->data)
+                return -ENODATA;
+
+        wrapper = want_wrapper ? pkcs7->data_hdrlen : 0;
+        *_data = pkcs7->data - wrapper;
+        *_data_len = pkcs7->data_len + wrapper;
+        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.pkey_hash_algo = HASH_ALGO_MD4;
+                break;
+        case OID_md5:
+                ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_MD5;
+                break;
+        case OID_sha1:
+                ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_SHA1;
+                break;
+        case OID_sha256:
+                ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_SHA256;
+                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 = PKEY_ALGO_RSA;
+                break;
+        default:
+                printk("Unsupported pkey algo: %u\n", ctx->last_oid);
+                return -ENOPKG;
+        }
+        return 0;
+}
+
+/*
+ * 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);
+
+        pr_debug("Got cert for %s\n", x509->subject);
+        pr_debug("- fingerprint %s\n", x509->fingerprint);
+
+        x509->index = ++ctx->x509_index;
+        *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;
+}
+
+/*
+ * 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;
+        ctx->msg->data_type = ctx->last_oid;
+        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;
+
+        pr_devel("AuthAttr: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
+
+        switch (ctx->last_oid) {
+        case OID_messageDigest:
+                if (tag != ASN1_OTS)
+                        return -EBADMSG;
+                ctx->sinfo->msgdigest = value;
+                ctx->sinfo->msgdigest_len = vlen;
+                return 0;
+        default:
+                return 0;
+        }
+}
+
+/*
+ * Note the set of auth attributes for digestion purposes [RFC2315 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;
+
+        /* We need to switch the 'CONT 0' to a 'SET OF' when we digest */
+        ctx->sinfo->authattrs = value - (hdrlen - 1);
+        ctx->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->sinfo->raw_serial = value;
+        ctx->sinfo->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->sinfo->raw_issuer = value;
+        ctx->sinfo->raw_issuer_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;
+        MPI mpi;
+
+        BUG_ON(ctx->sinfo->sig.pkey_algo != PKEY_ALGO_RSA);
+
+        mpi = mpi_read_raw_data(value, vlen);
+        if (!mpi)
+                return -ENOMEM;
+
+        ctx->sinfo->sig.mpi[0] = mpi;
+        ctx->sinfo->sig.nr_mpi = 1;
+        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;
+
+        ctx->sinfo->index = ++ctx->sinfo_index;
+        *ctx->ppsinfo = ctx->sinfo;
+        ctx->ppsinfo = &ctx->sinfo->next;
+        ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
+        if (!ctx->sinfo)
+                return -ENOMEM;
+        return 0;
+}
diff --git a/crypto/asymmetric_keys/pkcs7_parser.h b/crypto/asymmetric_keys/pkcs7_parser.h
new file mode 100644
index 000000000000..d25f4d15370f
--- /dev/null
+++ b/crypto/asymmetric_keys/pkcs7_parser.h
@@ -0,0 +1,61 @@
+/* PKCS#7 crypto data parser internal definitions
+ *
+ * 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.
+ */
+
+#include <linux/oid_registry.h>
+#include <crypto/pkcs7.h>
+#include "x509_parser.h"
+
+#define kenter(FMT, ...) \
+        pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+        pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
+
+struct pkcs7_signed_info {
+        struct pkcs7_signed_info *next;
+        struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
+        unsigned index;
+        bool trusted;
+
+        /* Message digest - the digest of the Content Data (or NULL) */
+        const void      *msgdigest;
+        unsigned        msgdigest_len;
+
+        /* Authenticated Attribute data (or NULL) */
+        unsigned        authattrs_len;
+        const void      *authattrs;
+
+        /* Issuing cert serial number and issuer's name */
+        const void      *raw_serial;
+        unsigned        raw_serial_size;
+        unsigned        raw_issuer_size;
+        const void      *raw_issuer;
+
+        /* Message signature.
+         *
+         * This contains the generated digest of _either_ the Content Data or
+         * the Authenticated Attributes [RFC2315 9.3].  If the latter, one of
+         * the attributes contains the digest of the the Content Data within
+         * it.
+         */
+        struct public_key_signature sig;
+};
+
+struct pkcs7_message {
+        struct x509_certificate *certs; /* Certificate list */
+        struct x509_certificate *crl;   /* Revocation list */
+        struct pkcs7_signed_info *signed_infos;
+
+        /* Content Data (or NULL) */
+        enum OID        data_type;      /* Type of Data */
+        size_t          data_len;       /* Length of Data */
+        size_t          data_hdrlen;    /* Length of Data ASN.1 header */
+        const void      *data;          /* Content Data (or 0) */
+};