Added stand-alone RSA/PSS implementation.

src/inner.h

@@ -1943,6 +1943,27 @@ uint32_t br_rsa_pkcs1_sig_unpad(const unsigned char *sig, size_t sig_len,
 	const unsigned char *hash_oid, size_t hash_len,
 	unsigned char *hash_out);
 
+/*
+ * Apply proper PSS padding. The 'x' buffer is output only: it
+ * receives the value that is to be exponentiated.
+ */
+uint32_t br_rsa_pss_sig_pad(const br_prng_class **rng,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	uint32_t n_bitlen, unsigned char *x);
+
+/*
+ * Check PSS padding. The provided value is the one _after_
+ * the modular exponentiation; it is modified by this function.
+ * This function infers the signature length from the public key
+ * size, i.e. it assumes that this has already been verified (as
+ * part of the exponentiation).
+ */
+uint32_t br_rsa_pss_sig_unpad(
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	const br_rsa_public_key *pk, unsigned char *x);
+
 /*
  * Apply OAEP padding. Returned value is the actual padded string length,
  * or zero on error.

src/rsa/rsa_default_pss_sign.c

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+br_rsa_pss_sign
+br_rsa_pss_sign_get_default(void)
+{
+#if BR_INT128 || BR_UMUL128
+	return &br_rsa_i62_pss_sign;
+#elif BR_LOMUL
+	return &br_rsa_i15_pss_sign;
+#else
+	return &br_rsa_i31_pss_sign;
+#endif
+}

src/rsa/rsa_default_pss_vrfy.c

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+br_rsa_pss_vrfy
+br_rsa_pss_vrfy_get_default(void)
+{
+#if BR_INT128 || BR_UMUL128
+	return &br_rsa_i62_pss_vrfy;
+#elif BR_LOMUL
+	return &br_rsa_i15_pss_vrfy;
+#else
+	return &br_rsa_i31_pss_vrfy;
+#endif
+}

src/rsa/rsa_i15_pss_sign.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i15_pss_sign(const br_prng_class **rng,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	const br_rsa_private_key *sk, unsigned char *x)
+{
+	if (!br_rsa_pss_sig_pad(rng, hf_data, hf_mgf1, hash,
+		salt_len, sk->n_bitlen, x))
+	{
+		return 0;
+	}
+	return br_rsa_i15_private(x, sk);
+}

src/rsa/rsa_i15_pss_vrfy.c

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i15_pss_vrfy(const unsigned char *x, size_t xlen,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const void *hash, size_t salt_len, const br_rsa_public_key *pk)
+{
+	unsigned char sig[BR_MAX_RSA_SIZE >> 3];
+
+	if (xlen > (sizeof sig)) {
+		return 0;
+	}
+	memcpy(sig, x, xlen);
+	if (!br_rsa_i15_public(sig, xlen, pk)) {
+		return 0;
+	}
+	return br_rsa_pss_sig_unpad(hf_data, hf_mgf1,
+		hash, salt_len, pk, sig);
+}

src/rsa/rsa_i31_pss_sign.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i31_pss_sign(const br_prng_class **rng,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	const br_rsa_private_key *sk, unsigned char *x)
+{
+	if (!br_rsa_pss_sig_pad(rng, hf_data, hf_mgf1, hash,
+		salt_len, sk->n_bitlen, x))
+	{
+		return 0;
+	}
+	return br_rsa_i31_private(x, sk);
+}

src/rsa/rsa_i31_pss_vrfy.c

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i31_pss_vrfy(const unsigned char *x, size_t xlen,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const void *hash, size_t salt_len, const br_rsa_public_key *pk)
+{
+	unsigned char sig[BR_MAX_RSA_SIZE >> 3];
+
+	if (xlen > (sizeof sig)) {
+		return 0;
+	}
+	memcpy(sig, x, xlen);
+	if (!br_rsa_i31_public(sig, xlen, pk)) {
+		return 0;
+	}
+	return br_rsa_pss_sig_unpad(hf_data, hf_mgf1,
+		hash, salt_len, pk, sig);
+}

src/rsa/rsa_i32_pss_sign.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i32_pss_sign(const br_prng_class **rng,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	const br_rsa_private_key *sk, unsigned char *x)
+{
+	if (!br_rsa_pss_sig_pad(rng, hf_data, hf_mgf1, hash,
+		salt_len, sk->n_bitlen, x))
+	{
+		return 0;
+	}
+	return br_rsa_i32_private(x, sk);
+}

src/rsa/rsa_i32_pss_vrfy.c

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i32_pss_vrfy(const unsigned char *x, size_t xlen,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const void *hash, size_t salt_len, const br_rsa_public_key *pk)
+{
+	unsigned char sig[BR_MAX_RSA_SIZE >> 3];
+
+	if (xlen > (sizeof sig)) {
+		return 0;
+	}
+	memcpy(sig, x, xlen);
+	if (!br_rsa_i32_public(sig, xlen, pk)) {
+		return 0;
+	}
+	return br_rsa_pss_sig_unpad(hf_data, hf_mgf1,
+		hash, salt_len, pk, sig);
+}

src/rsa/rsa_i62_pss_sign.c

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+#if BR_INT128 || BR_UMUL128
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i62_pss_sign(const br_prng_class **rng,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	const br_rsa_private_key *sk, unsigned char *x)
+{
+	if (!br_rsa_pss_sig_pad(rng, hf_data, hf_mgf1, hash,
+		salt_len, sk->n_bitlen, x))
+	{
+		return 0;
+	}
+	return br_rsa_i62_private(x, sk);
+}
+
+/* see bearssl_rsa.h */
+br_rsa_pss_sign
+br_rsa_i62_pss_sign_get(void)
+{
+	return &br_rsa_i62_pss_sign;
+}
+
+#else
+
+/* see bearssl_rsa.h */
+br_rsa_pss_sign
+br_rsa_i62_pss_sign_get(void)
+{
+	return 0;
+}
+
+#endif

src/rsa/rsa_i62_pss_vrfy.c

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+#if BR_INT128 || BR_UMUL128
+
+/* see bearssl_rsa.h */
+uint32_t
+br_rsa_i62_pss_vrfy(const unsigned char *x, size_t xlen,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const void *hash, size_t salt_len, const br_rsa_public_key *pk)
+{
+	unsigned char sig[BR_MAX_RSA_SIZE >> 3];
+
+	if (xlen > (sizeof sig)) {
+		return 0;
+	}
+	memcpy(sig, x, xlen);
+	if (!br_rsa_i62_public(sig, xlen, pk)) {
+		return 0;
+	}
+	return br_rsa_pss_sig_unpad(hf_data, hf_mgf1,
+		hash, salt_len, pk, sig);
+}
+
+/* see bearssl_rsa.h */
+br_rsa_pss_vrfy
+br_rsa_i62_pss_vrfy_get(void)
+{
+	return &br_rsa_i62_pss_vrfy;
+}
+
+#else
+
+/* see bearssl_rsa.h */
+br_rsa_pss_vrfy
+br_rsa_i62_pss_vrfy_get(void)
+{
+	return 0;
+}
+
+#endif

src/rsa/rsa_pss_sig_pad.c

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see inner.h */
+uint32_t
+br_rsa_pss_sig_pad(const br_prng_class **rng,
+	const br_hash_class *hf_data, const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	uint32_t n_bitlen, unsigned char *x)
+{
+	size_t xlen, hash_len;
+	br_hash_compat_context hc;
+	unsigned char *salt, *seed;
+
+	hash_len = br_digest_size(hf_data);
+
+	/*
+	 * The padded string is one bit smaller than the modulus;
+	 * notably, if the modulus length is equal to 1 modulo 8, then
+	 * the padded string will be one _byte_ smaller, and the first
+	 * byte will be set to 0. We apply these transformations here.
+	 */
+	n_bitlen --;
+	if ((n_bitlen & 7) == 0) {
+		*x ++ = 0;
+	}
+	xlen = (n_bitlen + 7) >> 3;
+
+	/*
+	 * Check that the modulus is large enough for the hash value
+	 * length combined with the intended salt length.
+	 */
+	if (hash_len > xlen || salt_len > xlen
+		|| (hash_len + salt_len + 2) > xlen)
+	{
+		return 0;
+	}
+
+	/*
+	 * Produce a random salt.
+	 */
+	salt = x + xlen - hash_len - salt_len - 1;
+	if (salt_len != 0) {
+		(*rng)->generate(rng, salt, salt_len);
+	}
+
+	/*
+	 * Compute the seed for MGF1.
+	 */
+	seed = x + xlen - hash_len - 1;
+	hf_data->init(&hc.vtable);
+	memset(seed, 0, 8);
+	hf_data->update(&hc.vtable, seed, 8);
+	hf_data->update(&hc.vtable, hash, hash_len);
+	hf_data->update(&hc.vtable, salt, salt_len);
+	hf_data->out(&hc.vtable, seed);
+
+	/*
+	 * Prepare string PS (padded salt). The salt is already at the
+	 * right place.
+	 */
+	memset(x, 0, xlen - salt_len - hash_len - 2);
+	x[xlen - salt_len - hash_len - 2] = 0x01;
+
+	/*
+	 * Generate the mask and XOR it into PS.
+	 */
+	br_mgf1_xor(x, xlen - hash_len - 1, hf_mgf1, seed, hash_len);
+
+	/*
+	 * Clear the top bits to ensure the value is lower than the
+	 * modulus.
+	 */
+	x[0] &= 0xFF >> (((uint32_t)xlen << 3) - n_bitlen);
+
+	/*
+	 * The seed (H) is already in the right place. We just set the
+	 * last byte.
+	 */
+	x[xlen - 1] = 0xBC;
+
+	return 1;
+}

src/rsa/rsa_pss_sig_unpad.c

@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see inner.h */
+uint32_t
+br_rsa_pss_sig_unpad(const br_hash_class *hf_data,
+	const br_hash_class *hf_mgf1,
+	const unsigned char *hash, size_t salt_len,
+	const br_rsa_public_key *pk, unsigned char *x)
+{
+	size_t u, xlen, hash_len;
+	br_hash_compat_context hc;
+	unsigned char *seed, *salt;
+	unsigned char tmp[64];
+	uint32_t r, n_bitlen;
+
+	hash_len = br_digest_size(hf_data);
+
+	/*
+	 * Value r will be set to a non-zero value is any test fails.
+	 */
+	r = 0;
+
+	/*
+	 * The value bit length (as an integer) must be strictly less than
+	 * that of the modulus.
+	 */
+	for (u = 0; u < pk->nlen; u ++) {
+		if (pk->n[u] != 0) {
+			break;
+		}
+	}
+	if (u == pk->nlen) {
+		return 0;
+	}
+	n_bitlen = BIT_LENGTH(pk->n[u]) + ((uint32_t)(pk->nlen - u - 1) << 3);
+	n_bitlen --;
+	if ((n_bitlen & 7) == 0) {
+		r |= *x ++;
+	} else {
+		r |= x[0] & (0xFF << (n_bitlen & 7));
+	}
+	xlen = (n_bitlen + 7) >> 3;
+
+	/*
+	 * Check that the modulus is large enough for the hash value
+	 * length combined with the intended salt length.
+	 */
+	if (hash_len > xlen || salt_len > xlen
+		|| (hash_len + salt_len + 2) > xlen)
+	{
+		return 0;
+	}
+
+	/*
+	 * Check value of rightmost byte.
+	 */
+	r |= x[xlen - 1] ^ 0xBC;
+
+	/*
+	 * Generate the mask and XOR it into the first bytes to reveal PS;
+	 * we must also mask out the leading bits.
+	 */
+	seed = x + xlen - hash_len - 1;
+	br_mgf1_xor(x, xlen - hash_len - 1, hf_mgf1, seed, hash_len);
+	if ((n_bitlen & 7) != 0) {
+		x[0] &= 0xFF >> (8 - (n_bitlen & 7));
+	}
+
+	/*
+	 * Check that all padding bytes have the expected value.
+	 */
+	for (u = 0; u < (xlen - hash_len - salt_len - 2); u ++) {
+		r |= x[u];
+	}
+	r |= x[xlen - hash_len - salt_len - 2] ^ 0x01;
+
+	/*
+	 * Recompute H.
+	 */
+	salt = x + xlen - hash_len - salt_len - 1;
+	hf_data->init(&hc.vtable);
+	memset(tmp, 0, 8);
+	hf_data->update(&hc.vtable, tmp, 8);
+	hf_data->update(&hc.vtable, hash, hash_len);
+	hf_data->update(&hc.vtable, salt, salt_len);
+	hf_data->out(&hc.vtable, tmp);
+
+	/*
+	 * Check that the recomputed H value matches the one appearing
+	 * in the string.
+	 */
+	for (u = 0; u < hash_len; u ++) {
+		r |= tmp[u] ^ x[(xlen - salt_len - 1) + u];
+	}
+
+	return EQ0(r);
+}