source: vendor/current/lib/util/asn1.c

/* 
   Unix SMB/CIFS implementation.
   simple ASN1 routines
   Copyright (C) Andrew Tridgell 2001
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/locale.h"
#include "lib/util/asn1.h"
#include "lib/util/debug.h"
#include "lib/util/samba_util.h"

struct nesting {
        off_t start;
        size_t taglen; /* for parsing */
        struct nesting *next;
};


struct asn1_data {
        uint8_t *data;
        size_t length;
        off_t ofs;
        struct nesting *nesting;
        bool has_error;
};

/* allocate an asn1 structure */
struct asn1_data *asn1_init(TALLOC_CTX *mem_ctx)
{
        struct asn1_data *ret = talloc_zero(mem_ctx, struct asn1_data);
        if (ret == NULL) {
                DEBUG(0,("asn1_init failed! out of memory\n"));
        }
        return ret;
}

/* free an asn1 structure */
void asn1_free(struct asn1_data *data)
{
        talloc_free(data);
}

bool asn1_has_error(const struct asn1_data *data)
{
        return data->has_error;
}

void asn1_set_error(struct asn1_data *data)
{
        data->has_error = true;
}

bool asn1_has_nesting(const struct asn1_data *data)
{
        return data->nesting != NULL;
}

off_t asn1_current_ofs(const struct asn1_data *data)
{
        return data->ofs;
}

/* write to the ASN1 buffer, advancing the buffer pointer */
bool asn1_write(struct asn1_data *data, const void *p, int len)
{
        if (data->has_error) return false;

        if ((len < 0) || (data->ofs + (size_t)len < data->ofs)) {
                data->has_error = true;
                return false;
        }

        if (data->length < data->ofs+len) {
                uint8_t *newp;
                newp = talloc_realloc(data, data->data, uint8_t, data->ofs+len);
                if (!newp) {
                        data->has_error = true;
                        return false;
                }
                data->data = newp;
                data->length = data->ofs+len;
        }
        memcpy(data->data + data->ofs, p, len);
        data->ofs += len;
        return true;
}

/* useful fn for writing a uint8_t */
bool asn1_write_uint8(struct asn1_data *data, uint8_t v)
{
        return asn1_write(data, &v, 1);
}

/* push a tag onto the asn1 data buffer. Used for nested structures */
bool asn1_push_tag(struct asn1_data *data, uint8_t tag)
{
        struct nesting *nesting;

        if (!asn1_write_uint8(data, tag)) {
                return false;
        }
        nesting = talloc(data, struct nesting);
        if (!nesting) {
                data->has_error = true;
                return false;
        }

        nesting->start = data->ofs;
        nesting->next = data->nesting;
        data->nesting = nesting;
        return asn1_write_uint8(data, 0xff);
}

/* pop a tag */
bool asn1_pop_tag(struct asn1_data *data)
{
        struct nesting *nesting;
        size_t len;

        if (data->has_error) {
                return false;
        }

        nesting = data->nesting;

        if (!nesting) {
                data->has_error = true;
                return false;
        }
        len = data->ofs - (nesting->start+1);
        /* yes, this is ugly. We don't know in advance how many bytes the length
           of a tag will take, so we assumed 1 byte. If we were wrong then we 
           need to correct our mistake */
        if (len > 0xFFFFFF) {
                data->data[nesting->start] = 0x84;
                if (!asn1_write_uint8(data, 0)) return false;
                if (!asn1_write_uint8(data, 0)) return false;
                if (!asn1_write_uint8(data, 0)) return false;
                if (!asn1_write_uint8(data, 0)) return false;
                memmove(data->data+nesting->start+5, data->data+nesting->start+1, len);
                data->data[nesting->start+1] = (len>>24) & 0xFF;
                data->data[nesting->start+2] = (len>>16) & 0xFF;
                data->data[nesting->start+3] = (len>>8) & 0xFF;
                data->data[nesting->start+4] = len&0xff;
        } else if (len > 0xFFFF) {
                data->data[nesting->start] = 0x83;
                if (!asn1_write_uint8(data, 0)) return false;
                if (!asn1_write_uint8(data, 0)) return false;
                if (!asn1_write_uint8(data, 0)) return false;
                memmove(data->data+nesting->start+4, data->data+nesting->start+1, len);
                data->data[nesting->start+1] = (len>>16) & 0xFF;
                data->data[nesting->start+2] = (len>>8) & 0xFF;
                data->data[nesting->start+3] = len&0xff;
        } else if (len > 255) {
                data->data[nesting->start] = 0x82;
                if (!asn1_write_uint8(data, 0)) return false;
                if (!asn1_write_uint8(data, 0)) return false;
                memmove(data->data+nesting->start+3, data->data+nesting->start+1, len);
                data->data[nesting->start+1] = len>>8;
                data->data[nesting->start+2] = len&0xff;
        } else if (len > 127) {
                data->data[nesting->start] = 0x81;
                if (!asn1_write_uint8(data, 0)) return false;
                memmove(data->data+nesting->start+2, data->data+nesting->start+1, len);
                data->data[nesting->start+1] = len;
        } else {
                data->data[nesting->start] = len;
        }

        data->nesting = nesting->next;
        talloc_free(nesting);
        return true;
}

/* "i" is the one's complement representation, as is the normal result of an
 * implicit signed->unsigned conversion */

static bool push_int_bigendian(struct asn1_data *data, unsigned int i, bool negative)
{
        uint8_t lowest = i & 0xFF;

        i = i >> 8;
        if (i != 0)
                if (!push_int_bigendian(data, i, negative))
                        return false;

        if (data->nesting->start+1 == data->ofs) {

                /* We did not write anything yet, looking at the highest
                 * valued byte */

                if (negative) {
                        /* Don't write leading 0xff's */
                        if (lowest == 0xFF)
                                return true;

                        if ((lowest & 0x80) == 0) {
                                /* The only exception for a leading 0xff is if
                                 * the highest bit is 0, which would indicate
                                 * a positive value */
                                if (!asn1_write_uint8(data, 0xff))
                                        return false;
                        }
                } else {
                        if (lowest & 0x80) {
                                /* The highest bit of a positive integer is 1,
                                 * this would indicate a negative number. Push
                                 * a 0 to indicate a positive one */
                                if (!asn1_write_uint8(data, 0))
                                        return false;
                        }
                }
        }

        return asn1_write_uint8(data, lowest);
}

/* write an Integer without the tag framing. Needed for example for the LDAP
 * Abandon Operation */

bool asn1_write_implicit_Integer(struct asn1_data *data, int i)
{
        if (data->has_error) {
                return false;
        }

        if (i == -1) {
                /* -1 is special as it consists of all-0xff bytes. In
                    push_int_bigendian this is the only case that is not
                    properly handled, as all 0xff bytes would be handled as
                    leading ones to be ignored. */
                return asn1_write_uint8(data, 0xff);
        } else {
                return push_int_bigendian(data, i, i<0);
        }
}


/* write an integer */
bool asn1_write_Integer(struct asn1_data *data, int i)
{
        if (!asn1_push_tag(data, ASN1_INTEGER)) return false;
        if (!asn1_write_implicit_Integer(data, i)) return false;
        return asn1_pop_tag(data);
}

/* write a BIT STRING */
bool asn1_write_BitString(struct asn1_data *data, const void *p, size_t length, uint8_t padding)
{
        if (!asn1_push_tag(data, ASN1_BIT_STRING)) return false;
        if (!asn1_write_uint8(data, padding)) return false;
        if (!asn1_write(data, p, length)) return false;
        return asn1_pop_tag(data);
}

bool ber_write_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB *blob, const char *OID)
{
        unsigned int v, v2;
        const char *p = (const char *)OID;
        char *newp;
        int i;

        if (!isdigit(*p)) return false;
        v = strtoul(p, &newp, 10);
        if (newp[0] != '.') return false;
        p = newp + 1;

        if (!isdigit(*p)) return false;
        v2 = strtoul(p, &newp, 10);
        if (newp[0] != '.') return false;
        p = newp + 1;

        /*the ber representation can't use more space than the string one */
        *blob = data_blob_talloc(mem_ctx, NULL, strlen(OID));
        if (!blob->data) return false;

        blob->data[0] = 40*v + v2;

        i = 1;
        while (*p) {
                if (!isdigit(*p)) return false;
                v = strtoul(p, &newp, 10);
                if (newp[0] == '.') {
                        p = newp + 1;
                        /* check for empty last component */
                        if (!*p) return false;
                } else if (newp[0] == '\0') {
                        p = newp;
                } else {
                        data_blob_free(blob);
                        return false;
                }
                if (v >= (1<<28)) blob->data[i++] = (0x80 | ((v>>28)&0x7f));
                if (v >= (1<<21)) blob->data[i++] = (0x80 | ((v>>21)&0x7f));
                if (v >= (1<<14)) blob->data[i++] = (0x80 | ((v>>14)&0x7f));
                if (v >= (1<<7)) blob->data[i++] = (0x80 | ((v>>7)&0x7f));
                blob->data[i++] = (v&0x7f);
        }

        blob->length = i;

        return true;
}

/**
 * Serialize partial OID string.
 * Partial OIDs are in the form:
 *   1:2.5.6:0x81
 *   1:2.5.6:0x8182
 */
bool ber_write_partial_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB *blob, const char *partial_oid)
{
        TALLOC_CTX *tmp_ctx = talloc_new(mem_ctx);
        char *oid = talloc_strdup(tmp_ctx, partial_oid);
        char *p;

        /* truncate partial part so ber_write_OID_String() works */
        p = strchr(oid, ':');
        if (p) {
                *p = '\0';
                p++;
        }

        if (!ber_write_OID_String(mem_ctx, blob, oid)) {
                talloc_free(tmp_ctx);
                return false;
        }

        /* Add partially encoded sub-identifier */
        if (p) {
                DATA_BLOB tmp_blob = strhex_to_data_blob(tmp_ctx, p);
                if (!data_blob_append(mem_ctx, blob, tmp_blob.data,
                                      tmp_blob.length)) {
                        talloc_free(tmp_ctx);
                        return false;
                }
        }

        talloc_free(tmp_ctx);

        return true;
}

/* write an object ID to a ASN1 buffer */
bool asn1_write_OID(struct asn1_data *data, const char *OID)
{
        DATA_BLOB blob;

        if (!asn1_push_tag(data, ASN1_OID)) return false;

        if (!ber_write_OID_String(NULL, &blob, OID)) {
                data->has_error = true;
                return false;
        }

        if (!asn1_write(data, blob.data, blob.length)) {
                data_blob_free(&blob);
                data->has_error = true;
                return false;
        }
        data_blob_free(&blob);
        return asn1_pop_tag(data);
}

/* write an octet string */
bool asn1_write_OctetString(struct asn1_data *data, const void *p, size_t length)
{
        if (!asn1_push_tag(data, ASN1_OCTET_STRING)) return false;
        if (!asn1_write(data, p, length)) return false;
        return asn1_pop_tag(data);
}

/* write a LDAP string */
bool asn1_write_LDAPString(struct asn1_data *data, const char *s)
{
        return asn1_write(data, s, strlen(s));
}

/* write a LDAP string from a DATA_BLOB */
bool asn1_write_DATA_BLOB_LDAPString(struct asn1_data *data, const DATA_BLOB *s)
{
        return asn1_write(data, s->data, s->length);
}

/* write a general string */
bool asn1_write_GeneralString(struct asn1_data *data, const char *s)
{
        if (!asn1_push_tag(data, ASN1_GENERAL_STRING)) return false;
        if (!asn1_write_LDAPString(data, s)) return false;
        return asn1_pop_tag(data);
}

bool asn1_write_ContextSimple(struct asn1_data *data, uint8_t num, DATA_BLOB *blob)
{
        if (!asn1_push_tag(data, ASN1_CONTEXT_SIMPLE(num))) return false;
        if (!asn1_write(data, blob->data, blob->length)) return false;
        return asn1_pop_tag(data);
}

/* write a BOOLEAN */
bool asn1_write_BOOLEAN(struct asn1_data *data, bool v)
{
        if (!asn1_push_tag(data, ASN1_BOOLEAN)) return false;
        if (!asn1_write_uint8(data, v ? 0xFF : 0)) return false;
        return asn1_pop_tag(data);
}

bool asn1_read_BOOLEAN(struct asn1_data *data, bool *v)
{
        uint8_t tmp = 0;
        if (!asn1_start_tag(data, ASN1_BOOLEAN)) return false;
        *v = false;
        if (!asn1_read_uint8(data, &tmp)) return false;
        if (tmp == 0xFF) {
                *v = true;
        }
        return asn1_end_tag(data);
}

/* write a BOOLEAN in a simple context */
bool asn1_write_BOOLEAN_context(struct asn1_data *data, bool v, int context)
{
        if (!asn1_push_tag(data, ASN1_CONTEXT_SIMPLE(context))) return false;
        if (!asn1_write_uint8(data, v ? 0xFF : 0)) return false;
        return asn1_pop_tag(data);
}

bool asn1_read_BOOLEAN_context(struct asn1_data *data, bool *v, int context)
{
        uint8_t tmp = 0;
        if (!asn1_start_tag(data, ASN1_CONTEXT_SIMPLE(context))) return false;
        *v = false;
        if (!asn1_read_uint8(data, &tmp)) return false;
        if (tmp == 0xFF) {
                *v = true;
        }
        return asn1_end_tag(data);
}

/* check a BOOLEAN */
bool asn1_check_BOOLEAN(struct asn1_data *data, bool v)
{
        uint8_t b = 0;

        if (!asn1_read_uint8(data, &b)) return false;
        if (b != ASN1_BOOLEAN) {
                data->has_error = true;
                return false;
        }
        if (!asn1_read_uint8(data, &b)) return false;
        if (b != v) {
                data->has_error = true;
                return false;
        }
        return !data->has_error;
}


/* load a struct asn1_data structure with a lump of data, ready to be parsed */
bool asn1_load(struct asn1_data *data, DATA_BLOB blob)
{
        ZERO_STRUCTP(data);
        data->data = (uint8_t *)talloc_memdup(data, blob.data, blob.length);
        if (!data->data) {
                data->has_error = true;
                return false;
        }
        data->length = blob.length;
        return true;
}

/* Peek into an ASN1 buffer, not advancing the pointer */
bool asn1_peek(struct asn1_data *data, void *p, int len)
{
        if (data->has_error)
                return false;

        if (len < 0 || data->ofs + len < data->ofs || data->ofs + len < len)
                return false;

        if (data->ofs + len > data->length) {
                /* we need to mark the buffer as consumed, so the caller knows
                   this was an out of data error, and not a decode error */
                data->ofs = data->length;
                return false;
        }

        memcpy(p, data->data + data->ofs, len);
        return true;
}

/* read from a ASN1 buffer, advancing the buffer pointer */
bool asn1_read(struct asn1_data *data, void *p, int len)
{
        if (!asn1_peek(data, p, len)) {
                data->has_error = true;
                return false;
        }

        data->ofs += len;
        return true;
}

/* read a uint8_t from a ASN1 buffer */
bool asn1_read_uint8(struct asn1_data *data, uint8_t *v)
{
        return asn1_read(data, v, 1);
}

bool asn1_peek_uint8(struct asn1_data *data, uint8_t *v)
{
        return asn1_peek(data, v, 1);
}

bool asn1_peek_tag(struct asn1_data *data, uint8_t tag)
{
        uint8_t b;

        if (asn1_tag_remaining(data) <= 0) {
                return false;
        }

        if (!asn1_peek_uint8(data, &b))
                return false;

        return (b == tag);
}

/*
 * just get the needed size the tag would consume
 */
static bool asn1_peek_tag_needed_size(struct asn1_data *data, uint8_t tag,
                                      size_t *size)
{
        off_t start_ofs = data->ofs;
        uint8_t b;
        size_t taglen = 0;

        if (data->has_error) {
                return false;
        }

        if (!asn1_read_uint8(data, &b)) {
                data->ofs = start_ofs;
                data->has_error = false;
                return false;
        }

        if (b != tag) {
                data->ofs = start_ofs;
                data->has_error = false;
                return false;
        }

        if (!asn1_read_uint8(data, &b)) {
                data->ofs = start_ofs;
                data->has_error = false;
                return false;
        }

        if (b & 0x80) {
                int n = b & 0x7f;
                if (!asn1_read_uint8(data, &b)) {
                        data->ofs = start_ofs;
                        data->has_error = false;
                        return false;
                }
                if (n > 4) {
                        /*
                         * We should not allow more than 4 bytes
                         * for the encoding of the tag length.
                         *
                         * Otherwise we'd overflow the taglen
                         * variable on 32 bit systems.
                         */
                        data->ofs = start_ofs;
                        data->has_error = false;
                        return false;
                }
                taglen = b;
                while (n > 1) {
                        if (!asn1_read_uint8(data, &b)) {
                                data->ofs = start_ofs;
                                data->has_error = false;
                                return false;
                        }
                        taglen = (taglen << 8) | b;
                        n--;
                }
        } else {
                taglen = b;
        }

        *size = (data->ofs - start_ofs) + taglen;

        data->ofs = start_ofs;
        data->has_error = false;
        return true;
}

/* start reading a nested asn1 structure */
bool asn1_start_tag(struct asn1_data *data, uint8_t tag)
{
        uint8_t b;
        struct nesting *nesting;
        
        if (!asn1_read_uint8(data, &b))
                return false;

        if (b != tag) {
                data->has_error = true;
                return false;
        }
        nesting = talloc(data, struct nesting);
        if (!nesting) {
                data->has_error = true;
                return false;
        }

        if (!asn1_read_uint8(data, &b)) {
                return false;
        }

        if (b & 0x80) {
                int n = b & 0x7f;
                if (!asn1_read_uint8(data, &b))
                        return false;
                nesting->taglen = b;
                while (n > 1) {
                        if (!asn1_read_uint8(data, &b)) 
                                return false;
                        nesting->taglen = (nesting->taglen << 8) | b;
                        n--;
                }
        } else {
                nesting->taglen = b;
        }
        nesting->start = data->ofs;
        nesting->next = data->nesting;
        data->nesting = nesting;
        if (asn1_tag_remaining(data) == -1) {
                return false;
        }
        return !data->has_error;
}

/* stop reading a tag */
bool asn1_end_tag(struct asn1_data *data)
{
        struct nesting *nesting;

        /* make sure we read it all */
        if (asn1_tag_remaining(data) != 0) {
                data->has_error = true;
                return false;
        }

        nesting = data->nesting;

        if (!nesting) {
                data->has_error = true;
                return false;
        }

        data->nesting = nesting->next;
        talloc_free(nesting);
        return true;
}

/* work out how many bytes are left in this nested tag */
int asn1_tag_remaining(struct asn1_data *data)
{
        int remaining;
        if (data->has_error) {
                return -1;
        }

        if (!data->nesting) {
                data->has_error = true;
                return -1;
        }
        remaining = data->nesting->taglen - (data->ofs - data->nesting->start);
        if (remaining > (data->length - data->ofs)) {
                data->has_error = true;
                return -1;
        }
        return remaining;
}

/**
 * Internal implementation for reading binary OIDs
 * Reading is done as far in the buffer as valid OID
 * till buffer ends or not valid sub-identifier is found.
 */
static bool _ber_read_OID_String_impl(TALLOC_CTX *mem_ctx, DATA_BLOB blob,
                                      char **OID, size_t *bytes_eaten)
{
        int i;
        uint8_t *b;
        unsigned int v;
        char *tmp_oid = NULL;

        if (blob.length < 2) return false;

        b = blob.data;

        tmp_oid = talloc_asprintf(mem_ctx, "%u",  b[0]/40);
        if (!tmp_oid) goto nomem;
        tmp_oid = talloc_asprintf_append_buffer(tmp_oid, ".%u",  b[0]%40);
        if (!tmp_oid) goto nomem;

        if (bytes_eaten != NULL) {
                *bytes_eaten = 0;
        }

        for(i = 1, v = 0; i < blob.length; i++) {
                v = (v<<7) | (b[i]&0x7f);
                if ( ! (b[i] & 0x80)) {
                        tmp_oid = talloc_asprintf_append_buffer(tmp_oid, ".%u",  v);
                        v = 0;
                        if (bytes_eaten)
                                *bytes_eaten = i+1;
                }
                if (!tmp_oid) goto nomem;
        }

        *OID = tmp_oid;
        return true;

nomem:
        return false;
}

/* read an object ID from a data blob */
bool ber_read_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB blob, char **OID)
{
        size_t bytes_eaten;

        if (!_ber_read_OID_String_impl(mem_ctx, blob, OID, &bytes_eaten))
                return false;

        return (bytes_eaten == blob.length);
}

/**
 * Deserialize partial OID string.
 * Partial OIDs are in the form:
 *   1:2.5.6:0x81
 *   1:2.5.6:0x8182
 */
bool ber_read_partial_OID_String(TALLOC_CTX *mem_ctx, DATA_BLOB blob,
                                 char **partial_oid)
{
        size_t bytes_left;
        size_t bytes_eaten;
        char *identifier = NULL;
        char *tmp_oid = NULL;

        if (!_ber_read_OID_String_impl(mem_ctx, blob, &tmp_oid, &bytes_eaten))
                return false;

        if (bytes_eaten < blob.length) {
                bytes_left = blob.length - bytes_eaten;
                identifier = hex_encode_talloc(mem_ctx, &blob.data[bytes_eaten], bytes_left);
                if (!identifier)        goto nomem;

                *partial_oid = talloc_asprintf_append_buffer(tmp_oid, ":0x%s", identifier);
                if (!*partial_oid)      goto nomem;
                TALLOC_FREE(identifier);
        } else {
                *partial_oid = tmp_oid;
        }

        return true;

nomem:
        TALLOC_FREE(identifier);
        TALLOC_FREE(tmp_oid);
        return false;
}

/* read an object ID from a ASN1 buffer */
bool asn1_read_OID(struct asn1_data *data, TALLOC_CTX *mem_ctx, char **OID)
{
        DATA_BLOB blob;
        int len;

        if (!asn1_start_tag(data, ASN1_OID)) return false;

        len = asn1_tag_remaining(data);
        if (len < 0) {
                data->has_error = true;
                return false;
        }

        blob = data_blob(NULL, len);
        if (!blob.data) {
                data->has_error = true;
                return false;
        }

        if (!asn1_read(data, blob.data, len)) return false;
        if (!asn1_end_tag(data)) {
                data_blob_free(&blob);
                return false;
        }

        if (!ber_read_OID_String(mem_ctx, blob, OID)) {
                data->has_error = true;
                data_blob_free(&blob);
                return false;
        }

        data_blob_free(&blob);
        return true;
}

/* check that the next object ID is correct */
bool asn1_check_OID(struct asn1_data *data, const char *OID)
{
        char *id;

        if (!asn1_read_OID(data, data, &id)) return false;

        if (strcmp(id, OID) != 0) {
                talloc_free(id);
                data->has_error = true;
                return false;
        }
        talloc_free(id);
        return true;
}

/* read a LDAPString from a ASN1 buffer */
bool asn1_read_LDAPString(struct asn1_data *data, TALLOC_CTX *mem_ctx, char **s)
{
        int len;
        len = asn1_tag_remaining(data);
        if (len < 0) {
                data->has_error = true;
                return false;
        }
        *s = talloc_array(mem_ctx, char, len+1);
        if (! *s) {
                data->has_error = true;
                return false;
        }
        (*s)[len] = 0;
        return asn1_read(data, *s, len);
}


/* read a GeneralString from a ASN1 buffer */
bool asn1_read_GeneralString(struct asn1_data *data, TALLOC_CTX *mem_ctx, char **s)
{
        if (!asn1_start_tag(data, ASN1_GENERAL_STRING)) return false;
        if (!asn1_read_LDAPString(data, mem_ctx, s)) return false;
        return asn1_end_tag(data);
}


/* read a octet string blob */
bool asn1_read_OctetString(struct asn1_data *data, TALLOC_CTX *mem_ctx, DATA_BLOB *blob)
{
        int len;
        ZERO_STRUCTP(blob);
        if (!asn1_start_tag(data, ASN1_OCTET_STRING)) return false;
        len = asn1_tag_remaining(data);
        if (len < 0) {
                data->has_error = true;
                return false;
        }
        *blob = data_blob_talloc(mem_ctx, NULL, len+1);
        if (!blob->data || blob->length < len) {
                data->has_error = true;
                return false;
        }
        if (!asn1_read(data, blob->data, len)) goto err;
        if (!asn1_end_tag(data)) goto err;
        blob->length--;
        blob->data[len] = 0;
        return true;

  err:

        data_blob_free(blob);
        *blob = data_blob_null;
        return false;
}

bool asn1_read_ContextSimple(struct asn1_data *data, uint8_t num, DATA_BLOB *blob)
{
        int len;
        ZERO_STRUCTP(blob);
        if (!asn1_start_tag(data, ASN1_CONTEXT_SIMPLE(num))) return false;
        len = asn1_tag_remaining(data);
        if (len < 0) {
                data->has_error = true;
                return false;
        }
        *blob = data_blob(NULL, len);
        if ((len != 0) && (!blob->data)) {
                data->has_error = true;
                return false;
        }
        if (!asn1_read(data, blob->data, len)) return false;
        return asn1_end_tag(data);
}

/* read an integer without tag*/
bool asn1_read_implicit_Integer(struct asn1_data *data, int *i)
{
        uint8_t b;
        bool first_byte = true;
        *i = 0;

        while (!data->has_error && asn1_tag_remaining(data)>0) {
                if (!asn1_read_uint8(data, &b)) return false;
                if (first_byte) {
                        if (b & 0x80) {
                                /* Number is negative.
                                   Set i to -1 for sign extend. */
                                *i = -1;
                        }
                        first_byte = false;
                }
                *i = (*i << 8) + b;
        }
        return !data->has_error;        
        
}

/* read an integer */
bool asn1_read_Integer(struct asn1_data *data, int *i)
{
        *i = 0;

        if (!asn1_start_tag(data, ASN1_INTEGER)) return false;
        if (!asn1_read_implicit_Integer(data, i)) return false;
        return asn1_end_tag(data);      
}

/* read a BIT STRING */
bool asn1_read_BitString(struct asn1_data *data, TALLOC_CTX *mem_ctx, DATA_BLOB *blob, uint8_t *padding)
{
        int len;
        ZERO_STRUCTP(blob);
        if (!asn1_start_tag(data, ASN1_BIT_STRING)) return false;
        len = asn1_tag_remaining(data);
        if (len < 0) {
                data->has_error = true;
                return false;
        }
        if (!asn1_read_uint8(data, padding)) return false;

        *blob = data_blob_talloc(mem_ctx, NULL, len+1);
        if (!blob->data || blob->length < len) {
                data->has_error = true;
                return false;
        }
        if (asn1_read(data, blob->data, len - 1)) {
                blob->length--;
                blob->data[len] = 0;
                asn1_end_tag(data);
        }

        if (data->has_error) {
                data_blob_free(blob);
                *blob = data_blob_null;
                *padding = 0;
                return false;
        }
        return true;
}

/* read an integer */
bool asn1_read_enumerated(struct asn1_data *data, int *v)
{
        *v = 0;
        
        if (!asn1_start_tag(data, ASN1_ENUMERATED)) return false;
        while (!data->has_error && asn1_tag_remaining(data)>0) {
                uint8_t b;
                if (!asn1_read_uint8(data, &b)) {
                        return false;
                }
                *v = (*v << 8) + b;
        }
        return asn1_end_tag(data);      
}

/* check a enumerated value is correct */
bool asn1_check_enumerated(struct asn1_data *data, int v)
{
        uint8_t b;
        if (!asn1_start_tag(data, ASN1_ENUMERATED)) return false;
        if (!asn1_read_uint8(data, &b)) return false;
        if (!asn1_end_tag(data)) return false;

        if (v != b)
                data->has_error = false;

        return !data->has_error;
}

/* write an enumerated value to the stream */
bool asn1_write_enumerated(struct asn1_data *data, uint8_t v)
{
        if (!asn1_push_tag(data, ASN1_ENUMERATED)) return false;
        if (!asn1_write_uint8(data, v)) return false;
        return asn1_pop_tag(data);
}

/*
  Get us the data just written without copying
*/
bool asn1_blob(const struct asn1_data *asn1, DATA_BLOB *blob)
{
        if (asn1->has_error) {
                return false;
        }
        if (asn1->nesting != NULL) {
                return false;
        }
        blob->data = asn1->data;
        blob->length = asn1->length;
        return true;
}

bool asn1_extract_blob(struct asn1_data *asn1, TALLOC_CTX *mem_ctx,
                       DATA_BLOB *pblob)
{
        DATA_BLOB blob;

        if (!asn1_blob(asn1, &blob)) {
                return false;
        }

        *pblob = (DATA_BLOB) { .length = blob.length };
        pblob->data = talloc_move(mem_ctx, &blob.data);

        /*
         * Stop access from here on
         */
        asn1->has_error = true;

        return true;
}

/*
  Fill in an asn1 struct without making a copy
*/
void asn1_load_nocopy(struct asn1_data *data, uint8_t *buf, size_t len)
{
        ZERO_STRUCTP(data);
        data->data = buf;
        data->length = len;
}

int asn1_peek_full_tag(DATA_BLOB blob, uint8_t tag, size_t *packet_size)
{
        struct asn1_data asn1;
        size_t size;
        bool ok;

        ZERO_STRUCT(asn1);
        asn1.data = blob.data;
        asn1.length = blob.length;

        ok = asn1_peek_tag_needed_size(&asn1, tag, &size);
        if (!ok) {
                return EMSGSIZE;
        }

        if (size > blob.length) {
                *packet_size = size;
                return EAGAIN;
        }               

        *packet_size = size;
        return 0;
}