// SPDX-License-Identifier: GPL-2.0+ and MIT
/*
 * RSA library - generate parameters for a public key
 *
 * Copyright (c) 2019 Linaro Limited
 * Author: AKASHI Takahiro
 *
 * Big number routines in this file come from BearSSL:
 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
 */

#include <common.h>
#include <image.h>
#include <malloc.h>
#include <crypto/internal/rsa.h>
#include <u-boot/rsa-mod-exp.h>
#include <asm/unaligned.h>

/**
 * br_dec16be() - Convert 16-bit big-endian integer to native
 * @src:        Pointer to data
 * Return:      Native-endian integer
 */
static unsigned br_dec16be(const void *src)
{
        return get_unaligned_be16(src);
}

/**
 * br_dec32be() - Convert 32-bit big-endian integer to native
 * @src:        Pointer to data
 * Return:      Native-endian integer
 */
static uint32_t br_dec32be(const void *src)
{
        return get_unaligned_be32(src);
}

/**
 * br_enc32be() - Convert native 32-bit integer to big-endian
 * @dst:        Pointer to buffer to store big-endian integer in
 * @x:          Native 32-bit integer
 */
static void br_enc32be(void *dst, uint32_t x)
{
        __be32 tmp;

        tmp = cpu_to_be32(x);
        memcpy(dst, &tmp, sizeof(tmp));
}

/* from BearSSL's src/inner.h */

/*
 * Negate a boolean.
 */
static uint32_t NOT(uint32_t ctl)
{
        return ctl ^ 1;
}

/*
 * Multiplexer: returns x if ctl == 1, y if ctl == 0.
 */
static uint32_t MUX(uint32_t ctl, uint32_t x, uint32_t y)
{
        return y ^ (-ctl & (x ^ y));
}

/*
 * Equality check: returns 1 if x == y, 0 otherwise.
 */
static uint32_t EQ(uint32_t x, uint32_t y)
{
        uint32_t q;

        q = x ^ y;
        return NOT((q | -q) >> 31);
}

/*
 * Inequality check: returns 1 if x != y, 0 otherwise.
 */
static uint32_t NEQ(uint32_t x, uint32_t y)
{
        uint32_t q;

        q = x ^ y;
        return (q | -q) >> 31;
}

/*
 * Comparison: returns 1 if x > y, 0 otherwise.
 */
static uint32_t GT(uint32_t x, uint32_t y)
{
        /*
         * If both x < 2^31 and y < 2^31, then y-x will have its high
         * bit set if x > y, cleared otherwise.
         *
         * If either x >= 2^31 or y >= 2^31 (but not both), then the
         * result is the high bit of x.
         *
         * If both x >= 2^31 and y >= 2^31, then we can virtually
         * subtract 2^31 from both, and we are back to the first case.
         * Since (y-2^31)-(x-2^31) = y-x, the subtraction is already
         * fine.
         */
        uint32_t z;

        z = y - x;
        return (z ^ ((x ^ y) & (x ^ z))) >> 31;
}

/*
 * Compute the bit length of a 32-bit integer. Returned value is between 0
 * and 32 (inclusive).
 */
static uint32_t BIT_LENGTH(uint32_t x)
{
        uint32_t k, c;

        k = NEQ(x, 0);
        c = GT(x, 0xFFFF); x = MUX(c, x >> 16, x); k += c << 4;
        c = GT(x, 0x00FF); x = MUX(c, x >>  8, x); k += c << 3;
        c = GT(x, 0x000F); x = MUX(c, x >>  4, x); k += c << 2;
        c = GT(x, 0x0003); x = MUX(c, x >>  2, x); k += c << 1;
        k += GT(x, 0x0001);
        return k;
}

#define GE(x, y)   NOT(GT(y, x))
#define LT(x, y)   GT(y, x)
#define MUL(x, y)   ((uint64_t)(x) * (uint64_t)(y))

/*
 * Integers 'i32'
 * --------------
 *
 * The 'i32' functions implement computations on big integers using
 * an internal representation as an array of 32-bit integers. For
 * an array x[]:
 *  -- x[0] contains the "announced bit length" of the integer
 *  -- x[1], x[2]... contain the value in little-endian order (x[1]
 *     contains the least significant 32 bits)
 *
 * Multiplications rely on the elementary 32x32->64 multiplication.
 *
 * The announced bit length specifies the number of bits that are
 * significant in the subsequent 32-bit words. Unused bits in the
 * last (most significant) word are set to 0; subsequent words are
 * uninitialized and need not exist at all.
 *
 * The execution time and memory access patterns of all computations
 * depend on the announced bit length, but not on the actual word
 * values. For modular integers, the announced bit length of any integer
 * modulo n is equal to the actual bit length of n; thus, computations
 * on modular integers are "constant-time" (only the modulus length may
 * leak).
 */

/*
 * Extract one word from an integer. The offset is counted in bits.
 * The word MUST entirely fit within the word elements corresponding
 * to the announced bit length of a[].
 */
static uint32_t br_i32_word(const uint32_t *a, uint32_t off)
{
        size_t u;
        unsigned j;

        u = (size_t)(off >> 5) + 1;
        j = (unsigned)off & 31;
        if (j == 0) {
                return a[u];
        } else {
                return (a[u] >> j) | (a[u + 1] << (32 - j));
        }
}

/* from BearSSL's src/int/i32_bitlen.c */

/*
 * Compute the actual bit length of an integer. The argument x should
 * point to the first (least significant) value word of the integer.
 * The len 'xlen' contains the number of 32-bit words to access.
 *
 * CT: value or length of x does not leak.
 */
static uint32_t br_i32_bit_length(uint32_t *x, size_t xlen)
{
        uint32_t tw, twk;

        tw = 0;
        twk = 0;
        while (xlen -- > 0) {
                uint32_t w, c;

                c = EQ(tw, 0);
                w = x[xlen];
                tw = MUX(c, w, tw);
                twk = MUX(c, (uint32_t)xlen, twk);
        }
        return (twk << 5) + BIT_LENGTH(tw);
}

/* from BearSSL's src/int/i32_decode.c */

/*
 * Decode an integer from its big-endian unsigned representation. The
 * "true" bit length of the integer is computed, but all words of x[]
 * corresponding to the full 'len' bytes of the source are set.
 *
 * CT: value or length of x does not leak.
 */
static void br_i32_decode(uint32_t *x, const void *src, size_t len)
{
        const unsigned char *buf;
        size_t u, v;

        buf = src;
        u = len;
        v = 1;
        for (;;) {
                if (u < 4) {
                        uint32_t w;

                        if (u < 2) {
                                if (u == 0) {
                                        break;
                                } else {
                                        w = buf[0];
                                }
                        } else {
                                if (u == 2) {
                                        w = br_dec16be(buf);
                                } else {
                                        w = ((uint32_t)buf[0] << 16)
                                                | br_dec16be(buf + 1);
                                }
                        }
                        x[v ++] = w;
                        break;
                } else {
                        u -= 4;
                        x[v ++] = br_dec32be(buf + u);
                }
        }
        x[0] = br_i32_bit_length(x + 1, v - 1);
}

/* from BearSSL's src/int/i32_encode.c */

/*
 * Encode an integer into its big-endian unsigned representation. The
 * output length in bytes is provided (parameter 'len'); if the length
 * is too short then the integer is appropriately truncated; if it is
 * too long then the extra bytes are set to 0.
 */
static void br_i32_encode(void *dst, size_t len, const uint32_t *x)
{
        unsigned char *buf;
        size_t k;

        buf = dst;

        /*
         * Compute the announced size of x in bytes; extra bytes are
         * filled with zeros.
         */
        k = (x[0] + 7) >> 3;
        while (len > k) {
                *buf ++ = 0;
                len --;
        }

        /*
         * Now we use k as index within x[]. That index starts at 1;
         * we initialize it to the topmost complete word, and process
         * any remaining incomplete word.
         */
        k = (len + 3) >> 2;
        switch (len & 3) {
        case 3:
                *buf ++ = x[k] >> 16;
                /* fall through */
        case 2:
                *buf ++ = x[k] >> 8;
                /* fall through */
        case 1:
                *buf ++ = x[k];
                k --;
        }

        /*
         * Encode all complete words.
         */
        while (k > 0) {
                br_enc32be(buf, x[k]);
                k --;
                buf += 4;
        }
}

/* from BearSSL's src/int/i32_ninv32.c */

/*
 * Compute -(1/x) mod 2^32. If x is even, then this function returns 0.
 */
static uint32_t br_i32_ninv32(uint32_t x)
{
        uint32_t y;

        y = 2 - x;
        y *= 2 - y * x;
        y *= 2 - y * x;
        y *= 2 - y * x;
        y *= 2 - y * x;
        return MUX(x & 1, -y, 0);
}

/* from BearSSL's src/int/i32_add.c */

/*
 * Add b[] to a[] and return the carry (0 or 1). If ctl is 0, then a[]
 * is unmodified, but the carry is still computed and returned. The
 * arrays a[] and b[] MUST have the same announced bit length.
 *
 * a[] and b[] MAY be the same array, but partial overlap is not allowed.
 */
static uint32_t br_i32_add(uint32_t *a, const uint32_t *b, uint32_t ctl)
{
        uint32_t cc;
        size_t u, m;

        cc = 0;
        m = (a[0] + 63) >> 5;
        for (u = 1; u < m; u ++) {
                uint32_t aw, bw, naw;

                aw = a[u];
                bw = b[u];
                naw = aw + bw + cc;

                /*
                 * Carry is 1 if naw < aw. Carry is also 1 if naw == aw
                 * AND the carry was already 1.
                 */
                cc = (cc & EQ(naw, aw)) | LT(naw, aw);
                a[u] = MUX(ctl, naw, aw);
        }
        return cc;
}

/* from BearSSL's src/int/i32_sub.c */

/*
 * Subtract b[] from a[] and return the carry (0 or 1). If ctl is 0,
 * then a[] is unmodified, but the carry is still computed and returned.
 * The arrays a[] and b[] MUST have the same announced bit length.
 *
 * a[] and b[] MAY be the same array, but partial overlap is not allowed.
 */
static uint32_t br_i32_sub(uint32_t *a, const uint32_t *b, uint32_t ctl)
{
        uint32_t cc;
        size_t u, m;

        cc = 0;
        m = (a[0] + 63) >> 5;
        for (u = 1; u < m; u ++) {
                uint32_t aw, bw, naw;

                aw = a[u];
                bw = b[u];
                naw = aw - bw - cc;

                /*
                 * Carry is 1 if naw > aw. Carry is 1 also if naw == aw
                 * AND the carry was already 1.
                 */
                cc = (cc & EQ(naw, aw)) | GT(naw, aw);
                a[u] = MUX(ctl, naw, aw);
        }
        return cc;
}

/* from BearSSL's src/int/i32_div32.c */

/*
 * Constant-time division. The dividend hi:lo is divided by the
 * divisor d; the quotient is returned and the remainder is written
 * in *r. If hi == d, then the quotient does not fit on 32 bits;
 * returned value is thus truncated. If hi > d, returned values are
 * indeterminate.
 */
static uint32_t br_divrem(uint32_t hi, uint32_t lo, uint32_t d, uint32_t *r)
{
        /* TODO: optimize this */
        uint32_t q;
        uint32_t ch, cf;
        int k;

        q = 0;
        ch = EQ(hi, d);
        hi = MUX(ch, 0, hi);
        for (k = 31; k > 0; k --) {
                int j;
                uint32_t w, ctl, hi2, lo2;

                j = 32 - k;
                w = (hi << j) | (lo >> k);
                ctl = GE(w, d) | (hi >> k);
                hi2 = (w - d) >> j;
                lo2 = lo - (d << k);
                hi = MUX(ctl, hi2, hi);
                lo = MUX(ctl, lo2, lo);
                q |= ctl << k;
        }
        cf = GE(lo, d) | hi;
        q |= cf;
        *r = MUX(cf, lo - d, lo);
        return q;
}

/*
 * Wrapper for br_divrem(); the remainder is returned, and the quotient
 * is discarded.
 */
static uint32_t br_rem(uint32_t hi, uint32_t lo, uint32_t d)
{
        uint32_t r;

        br_divrem(hi, lo, d, &r);
        return r;
}

/*
 * Wrapper for br_divrem(); the quotient is returned, and the remainder
 * is discarded.
 */
static uint32_t br_div(uint32_t hi, uint32_t lo, uint32_t d)
{
        uint32_t r;

        return br_divrem(hi, lo, d, &r);
}

/* from BearSSL's src/int/i32_muladd.c */

/*
 * Multiply x[] by 2^32 and then add integer z, modulo m[]. This
 * function assumes that x[] and m[] have the same announced bit
 * length, and the announced bit length of m[] matches its true
 * bit length.
 *
 * x[] and m[] MUST be distinct arrays.
 *
 * CT: only the common announced bit length of x and m leaks, not
 * the values of x, z or m.
 */
static void br_i32_muladd_small(uint32_t *x, uint32_t z, const uint32_t *m)
{
        uint32_t m_bitlen;
        size_t u, mlen;
        uint32_t a0, a1, b0, hi, g, q, tb;
        uint32_t chf, clow, under, over;
        uint64_t cc;

        /*
         * We can test on the modulus bit length since we accept to
         * leak that length.
         */
        m_bitlen = m[0];
        if (m_bitlen == 0) {
                return;
        }
        if (m_bitlen <= 32) {
                x[1] = br_rem(x[1], z, m[1]);
                return;
        }
        mlen = (m_bitlen + 31) >> 5;

        /*
         * Principle: we estimate the quotient (x*2^32+z)/m by
         * doing a 64/32 division with the high words.
         *
         * Let:
         *   w = 2^32
         *   a = (w*a0 + a1) * w^N + a2
         *   b = b0 * w^N + b2
         * such that:
         *   0 <= a0 < w
         *   0 <= a1 < w
         *   0 <= a2 < w^N
         *   w/2 <= b0 < w
         *   0 <= b2 < w^N
         *   a < w*b
         * I.e. the two top words of a are a0:a1, the top word of b is
         * b0, we ensured that b0 is "full" (high bit set), and a is
         * such that the quotient q = a/b fits on one word (0 <= q < w).
         *
         * If a = b*q + r (with 0 <= r < q), we can estimate q by
         * doing an Euclidean division on the top words:
         *   a0*w+a1 = b0*u + v  (with 0 <= v < w)
         * Then the following holds:
         *   0 <= u <= w
         *   u-2 <= q <= u
         */
        a0 = br_i32_word(x, m_bitlen - 32);
        hi = x[mlen];
        memmove(x + 2, x + 1, (mlen - 1) * sizeof *x);
        x[1] = z;
        a1 = br_i32_word(x, m_bitlen - 32);
        b0 = br_i32_word(m, m_bitlen - 32);

        /*
         * We estimate a divisor q. If the quotient returned by br_div()
         * is g:
         * -- If a0 == b0 then g == 0; we want q = 0xFFFFFFFF.
         * -- Otherwise:
         *    -- if g == 0 then we set q = 0;
         *    -- otherwise, we set q = g - 1.
         * The properties described above then ensure that the true
         * quotient is q-1, q or q+1.
         */
        g = br_div(a0, a1, b0);
        q = MUX(EQ(a0, b0), 0xFFFFFFFF, MUX(EQ(g, 0), 0, g - 1));

        /*
         * We subtract q*m from x (with the extra high word of value 'hi').
         * Since q may be off by 1 (in either direction), we may have to
         * add or subtract m afterwards.
         *
         * The 'tb' flag will be true (1) at the end of the loop if the
         * result is greater than or equal to the modulus (not counting
         * 'hi' or the carry).
         */
        cc = 0;
        tb = 1;
        for (u = 1; u <= mlen; u ++) {
                uint32_t mw, zw, xw, nxw;
                uint64_t zl;

                mw = m[u];
                zl = MUL(mw, q) + cc;
                cc = (uint32_t)(zl >> 32);
                zw = (uint32_t)zl;
                xw = x[u];
                nxw = xw - zw;
                cc += (uint64_t)GT(nxw, xw);
                x[u] = nxw;
                tb = MUX(EQ(nxw, mw), tb, GT(nxw, mw));
        }

        /*
         * If we underestimated q, then either cc < hi (one extra bit
         * beyond the top array word), or cc == hi and tb is true (no
         * extra bit, but the result is not lower than the modulus). In
         * these cases we must subtract m once.
         *
         * Otherwise, we may have overestimated, which will show as
         * cc > hi (thus a negative result). Correction is adding m once.
         */
        chf = (uint32_t)(cc >> 32);
        clow = (uint32_t)cc;
        over = chf | GT(clow, hi);
        under = ~over & (tb | (~chf & LT(clow, hi)));
        br_i32_add(x, m, over);
        br_i32_sub(x, m, under);
}

/* from BearSSL's src/int/i32_reduce.c */

/*
 * Reduce an integer (a[]) modulo another (m[]). The result is written
 * in x[] and its announced bit length is set to be equal to that of m[].
 *
 * x[] MUST be distinct from a[] and m[].
 *
 * CT: only announced bit lengths leak, not values of x, a or m.
 */
static void br_i32_reduce(uint32_t *x, const uint32_t *a, const uint32_t *m)
{
        uint32_t m_bitlen, a_bitlen;
        size_t mlen, alen, u;

        m_bitlen = m[0];
        mlen = (m_bitlen + 31) >> 5;

        x[0] = m_bitlen;
        if (m_bitlen == 0) {
                return;
        }

        /*
         * If the source is shorter, then simply copy all words from a[]
         * and zero out the upper words.
         */
        a_bitlen = a[0];
        alen = (a_bitlen + 31) >> 5;
        if (a_bitlen < m_bitlen) {
                memcpy(x + 1, a + 1, alen * sizeof *a);
                for (u = alen; u < mlen; u ++) {
                        x[u + 1] = 0;
                }
                return;
        }

        /*
         * The source length is at least equal to that of the modulus.
         * We must thus copy N-1 words, and input the remaining words
         * one by one.
         */
        memcpy(x + 1, a + 2 + (alen - mlen), (mlen - 1) * sizeof *a);
        x[mlen] = 0;
        for (u = 1 + alen - mlen; u > 0; u --) {
                br_i32_muladd_small(x, a[u], m);
        }
}

/**
 * rsa_free_key_prop() - Free key properties
 * @prop:       Pointer to struct key_prop
 *
 * This function frees all the memories allocated by rsa_gen_key_prop().
 */
void rsa_free_key_prop(struct key_prop *prop)
{
        if (!prop)
                return;

        free((void *)prop->modulus);
        free((void *)prop->public_exponent);
        free((void *)prop->rr);

        free(prop);
}

/**
 * rsa_gen_key_prop() - Generate key properties of RSA public key
 * @key:        Specifies key data in DER format
 * @keylen:     Length of @key
 * @prop:       Generated key property
 *
 * This function takes a blob of encoded RSA public key data in DER
 * format, parse it and generate all the relevant properties
 * in key_prop structure.
 * Return a pointer to struct key_prop in @prop on success.
 *
 * Return:      0 on success, negative on error
 */
int rsa_gen_key_prop(const void *key, uint32_t keylen, struct key_prop **prop)
{
        struct rsa_key rsa_key;
        uint32_t *n = NULL, *rr = NULL, *rrtmp = NULL;
        int rlen, i, ret = 0;

        *prop = calloc(sizeof(**prop), 1);
        if (!(*prop)) {
                ret = -ENOMEM;
                goto out;
        }

        ret = rsa_parse_pub_key(&rsa_key, key, keylen);
        if (ret)
                goto out;

        /* modulus */
        /* removing leading 0's */
        for (i = 0; i < rsa_key.n_sz && !rsa_key.n[i]; i++)
                ;
        (*prop)->num_bits = (rsa_key.n_sz - i) * 8;
        (*prop)->modulus = malloc(rsa_key.n_sz - i);
        if (!(*prop)->modulus) {
                ret = -ENOMEM;
                goto out;
        }
        memcpy((void *)(*prop)->modulus, &rsa_key.n[i], rsa_key.n_sz - i);

        n = calloc(sizeof(uint32_t), 1 + ((*prop)->num_bits >> 5));
        rr = calloc(sizeof(uint32_t), 1 + (((*prop)->num_bits * 2) >> 5));
        rrtmp = calloc(sizeof(uint32_t), 2 + (((*prop)->num_bits * 2) >> 5));
        if (!n || !rr || !rrtmp) {
                ret = -ENOMEM;
                goto out;
        }

        /* exponent */
        (*prop)->public_exponent = calloc(1, sizeof(uint64_t));
        if (!(*prop)->public_exponent) {
                ret = -ENOMEM;
                goto out;
        }
        memcpy((void *)(*prop)->public_exponent + sizeof(uint64_t)
                                                - rsa_key.e_sz,
               rsa_key.e, rsa_key.e_sz);
        (*prop)->exp_len = sizeof(uint64_t);

        /* n0 inverse */
        br_i32_decode(n, &rsa_key.n[i], rsa_key.n_sz - i);
        (*prop)->n0inv = br_i32_ninv32(n[1]);

        /* R^2 mod n; R = 2^(num_bits) */
        rlen = (*prop)->num_bits * 2; /* #bits of R^2 = (2^num_bits)^2 */
        rr[0] = 0;
        *(uint8_t *)&rr[0] = (1 << (rlen % 8));
        for (i = 1; i < (((rlen + 31) >> 5) + 1); i++)
                rr[i] = 0;
        br_i32_decode(rrtmp, rr, ((rlen + 7) >> 3) + 1);
        br_i32_reduce(rr, rrtmp, n);

        rlen = ((*prop)->num_bits + 7) >> 3; /* #bytes of R^2 mod n */
        (*prop)->rr = malloc(rlen);
        if (!(*prop)->rr) {
                ret = -ENOMEM;
                goto out;
        }
        br_i32_encode((void *)(*prop)->rr, rlen, rr);

out:
        free(n);
        free(rr);
        free(rrtmp);
        if (ret < 0)
                rsa_free_key_prop(*prop);
        return ret;
}