u-boot/lib/rsa/rsa-keyprop.c

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// 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 <asm/byteorder.h>
#include <crypto/internal/rsa.h>
#include <u-boot/rsa-mod-exp.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 be16_to_cpup(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 be32_to_cpup(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;
const int max_rsa_size = 4096;
int rlen, i, ret;
*prop = calloc(sizeof(**prop), 1);
n = calloc(sizeof(uint32_t), 1 + (max_rsa_size >> 5));
rr = calloc(sizeof(uint32_t), 1 + (max_rsa_size >> 5));
rrtmp = calloc(sizeof(uint32_t), 1 + (max_rsa_size >> 5));
if (!(*prop) || !n || !rr || !rrtmp) {
ret = -ENOMEM;
goto err;
}
ret = rsa_parse_pub_key(&rsa_key, key, keylen);
if (ret)
goto err;
/* 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 err;
}
memcpy((void *)(*prop)->modulus, &rsa_key.n[i], rsa_key.n_sz - i);
/* exponent */
(*prop)->public_exponent = calloc(1, sizeof(uint64_t));
if (!(*prop)->public_exponent) {
ret = -ENOMEM;
goto err;
}
memcpy((void *)(*prop)->public_exponent + sizeof(uint64_t)
- rsa_key.e_sz,
rsa_key.e, rsa_key.e_sz);
(*prop)->exp_len = rsa_key.e_sz;
/* 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 err;
}
br_i32_encode((void *)(*prop)->rr, rlen, rr);
return 0;
err:
free(n);
free(rr);
free(rrtmp);
rsa_free_key_prop(*prop);
return ret;
}