/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "secder.h"
#include <limits.h>
#include "secerr.h"

int
DER_LengthLength(PRUint32 len)
{
    if (len > 127) {
        if (len > 255) {
            if (len > 65535L) {
                if (len > 16777215L) {
                    return 5;
                } else {
                    return 4;
                }
            } else {
                return 3;
            }
        } else {
            return 2;
        }
    } else {
        return 1;
    }
}

unsigned char *
DER_StoreHeader(unsigned char *buf, unsigned int code, PRUint32 len)
{
    unsigned char b[4];

    b[0] = (unsigned char)(len >> 24);
    b[1] = (unsigned char)(len >> 16);
    b[2] = (unsigned char)(len >> 8);
    b[3] = (unsigned char)len;
    if ((code & DER_TAGNUM_MASK) == DER_SET || (code & DER_TAGNUM_MASK) == DER_SEQUENCE)
        code |= DER_CONSTRUCTED;
    *buf++ = code;
    if (len > 127) {
        if (len > 255) {
            if (len > 65535) {
                if (len > 16777215) {
                    *buf++ = 0x84;
                    *buf++ = b[0];
                    *buf++ = b[1];
                    *buf++ = b[2];
                    *buf++ = b[3];
                } else {
                    *buf++ = 0x83;
                    *buf++ = b[1];
                    *buf++ = b[2];
                    *buf++ = b[3];
                }
            } else {
                *buf++ = 0x82;
                *buf++ = b[2];
                *buf++ = b[3];
            }
        } else {
            *buf++ = 0x81;
            *buf++ = b[3];
        }
    } else {
        *buf++ = b[3];
    }
    return buf;
}

/*
 * XXX This should be rewritten, generalized, to take a long instead
 * of a PRInt32.
 */
SECStatus
DER_SetInteger(PLArenaPool *arena, SECItem *it, PRInt32 i)
{
    unsigned char bb[4];
    unsigned len;

    bb[0] = (unsigned char)(i >> 24);
    bb[1] = (unsigned char)(i >> 16);
    bb[2] = (unsigned char)(i >> 8);
    bb[3] = (unsigned char)(i);

    /*
    ** Small integers are encoded in a single byte. Larger integers
    ** require progressively more space.
    */
    if (i < -128) {
        if (i < -32768L) {
            if (i < -8388608L) {
                len = 4;
            } else {
                len = 3;
            }
        } else {
            len = 2;
        }
    } else if (i > 127) {
        if (i > 32767L) {
            if (i > 8388607L) {
                len = 4;
            } else {
                len = 3;
            }
        } else {
            len = 2;
        }
    } else {
        len = 1;
    }
    it->data = (unsigned char *)PORT_ArenaAlloc(arena, len);
    if (!it->data) {
        return SECFailure;
    }
    it->len = len;
    PORT_Memcpy(it->data, bb + (4 - len), len);
    return SECSuccess;
}

/*
 * XXX This should be rewritten, generalized, to take an unsigned long instead
 * of a PRUint32.
 */
SECStatus
DER_SetUInteger(PLArenaPool *arena, SECItem *it, PRUint32 ui)
{
    unsigned char bb[5];
    int len;

    bb[0] = 0;
    bb[1] = (unsigned char)(ui >> 24);
    bb[2] = (unsigned char)(ui >> 16);
    bb[3] = (unsigned char)(ui >> 8);
    bb[4] = (unsigned char)(ui);

    /*
    ** Small integers are encoded in a single byte. Larger integers
    ** require progressively more space.
    */
    if (ui > 0x7f) {
        if (ui > 0x7fff) {
            if (ui > 0x7fffffL) {
                if (ui >= 0x80000000L) {
                    len = 5;
                } else {
                    len = 4;
                }
            } else {
                len = 3;
            }
        } else {
            len = 2;
        }
    } else {
        len = 1;
    }

    it->data = (unsigned char *)PORT_ArenaAlloc(arena, len);
    if (it->data == NULL) {
        return SECFailure;
    }

    it->len = len;
    PORT_Memcpy(it->data, bb + (sizeof(bb) - len), len);

    return SECSuccess;
}

/*
** Convert a der encoded *signed* integer into a machine integral value.
** If an underflow/overflow occurs, sets error code and returns min/max.
*/
long
DER_GetInteger(const SECItem *it)
{
    unsigned long ival;
    PRBool negative;
    unsigned int len = it->len;
    unsigned char *cp = it->data;
    size_t lsize = sizeof(ival);

    PORT_Assert(len);
    if (!len) {
        PORT_SetError(SEC_ERROR_INPUT_LEN);
        return 0;
    }

    negative = (PRBool)(*cp & 0x80);
    ival = negative ? ~0 : 0;

    /* Ignore leading zeros/ones. */
    while (len && *cp == (unsigned char)ival) {
        len--;
        cp++;
    }

    /* Check for overflow/underflow. */
    if (len > lsize || (len == lsize && (*cp & 0x80) != negative)) {
        PORT_SetError(SEC_ERROR_BAD_DER);
        return negative ? LONG_MIN : LONG_MAX;
    }

    while (len--) {
        ival <<= 8;
        ival |= *cp++;
    }

    return ival;
}

/*
** Convert a der encoded *unsigned* integer into a machine integral value.
** If an overflow occurs, sets error code and returns max.
*/
unsigned long
DER_GetUInteger(SECItem *it)
{
    unsigned long ival = 0;
    unsigned len = it->len;
    unsigned char *cp = it->data;
    unsigned long overflow = 0xffUL << ((sizeof(ival) - 1) * 8);

    PORT_Assert(len);
    if (!len) {
        PORT_SetError(SEC_ERROR_INPUT_LEN);
        return 0;
    }

    /* Cannot put a negative value into an unsigned container. */
    if (*cp & 0x80) {
        PORT_SetError(SEC_ERROR_BAD_DER);
        return 0;
    }

    while (len) {
        if (ival & overflow) {
            PORT_SetError(SEC_ERROR_BAD_DER);
            return ULONG_MAX;
        }
        ival = ival << 8;
        ival |= *cp++;
        --len;
    }
    return ival;
}