Added RSA/OAEP implementation.

src/hash/mgf1.c

@@ -0,0 +1,56 @@
+/*
+ * 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 */
+void
+br_mgf1_xor(void *data, size_t len,
+	const br_hash_class *dig, const void *seed, size_t seed_len)
+{
+	unsigned char *buf;
+	size_t u, hlen;
+	uint32_t c;
+
+	buf = data;
+	hlen = br_digest_size(dig);
+	for (u = 0, c = 0; u < len; u += hlen, c ++) {
+		br_hash_compat_context hc;
+		unsigned char tmp[64];
+		size_t v;
+
+		hc.vtable = dig;
+		dig->init(&hc.vtable);
+		dig->update(&hc.vtable, seed, seed_len);
+		br_enc32be(tmp, c);
+		dig->update(&hc.vtable, tmp, 4);
+		dig->out(&hc.vtable, tmp);
+		for (v = 0; v < hlen; v ++) {
+			if ((u + v) >= len) {
+				break;
+			}
+			buf[u + v] ^= tmp[v];
+		}
+	}
+}

src/inner.h

@@ -1887,6 +1887,31 @@ 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 OAEP padding. Returned value is the actual padded string length,
+ * or zero on error.
+ */
+size_t br_rsa_oaep_pad(const br_prng_class **rnd, const br_hash_class *dig,
+	const void *label, size_t label_len, const br_rsa_public_key *pk,
+	void *dst, size_t dst_nax_len, const void *src, size_t src_len);
+
+/*
+ * Unravel and check OAEP padding. If the padding is correct, then 1 is
+ * returned, '*len' is adjusted to the length of the message, and the
+ * data is moved to the start of the 'data' buffer. If the padding is
+ * incorrect, then 0 is returned and '*len' is untouched. Either way,
+ * the complete buffer contents are altered.
+ */
+uint32_t br_rsa_oaep_unpad(const br_hash_class *dig,
+	const void *label, size_t label_len, void *data, size_t *len);
+
+/*
+ * Compute MGF1 for a given seed, and XOR the output into the provided
+ * buffer.
+ */
+void br_mgf1_xor(void *data, size_t len,
+	const br_hash_class *dig, const void *seed, size_t seed_len);
+
 /* ==================================================================== */
 /*
  * Elliptic curves.

src/rsa/rsa_default_oaep_decrypt.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_oaep_decrypt
+br_rsa_oaep_decrypt_get_default(void)
+{
+#if BR_INT128 || BR_UMUL128
+	return &br_rsa_i62_oaep_decrypt;
+#elif BR_LOMUL
+	return &br_rsa_i15_oaep_decrypt;
+#else
+	return &br_rsa_i31_oaep_decrypt;
+#endif
+}

src/rsa/rsa_default_oaep_encrypt.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_oaep_encrypt
+br_rsa_oaep_encrypt_get_default(void)
+{
+#if BR_INT128 || BR_UMUL128
+	return &br_rsa_i62_oaep_encrypt;
+#elif BR_LOMUL
+	return &br_rsa_i15_oaep_encrypt;
+#else
+	return &br_rsa_i31_oaep_encrypt;
+#endif
+}

src/rsa/rsa_i15_oaep_decrypt.c

@@ -0,0 +1,41 @@
+/*
+ * 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_oaep_decrypt(const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_private_key *sk, void *data, size_t *len)
+{
+	uint32_t r;
+
+	if (*len != ((sk->n_bitlen + 7) >> 3)) {
+		return 0;
+	}
+	r = br_rsa_i15_private(data, sk);
+	r &= br_rsa_oaep_unpad(dig, label, label_len, data, len);
+	return r;
+}

src/rsa/rsa_i15_oaep_encrypt.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 */
+size_t
+br_rsa_i15_oaep_encrypt(
+	const br_prng_class **rnd, const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_public_key *pk,
+	void *dst, size_t dst_max_len,
+	const void *src, size_t src_len)
+{
+	size_t dlen;
+
+	dlen = br_rsa_oaep_pad(rnd, dig, label, label_len,
+		pk, dst, dst_max_len, src, src_len);
+	if (dlen == 0) {
+		return 0;
+	}
+	return dlen & -(size_t)br_rsa_i15_public(dst, dlen, pk);
+}

src/rsa/rsa_i31_oaep_decrypt.c

@@ -0,0 +1,41 @@
+/*
+ * 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_oaep_decrypt(const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_private_key *sk, void *data, size_t *len)
+{
+	uint32_t r;
+
+	if (*len != ((sk->n_bitlen + 7) >> 3)) {
+		return 0;
+	}
+	r = br_rsa_i31_private(data, sk);
+	r &= br_rsa_oaep_unpad(dig, label, label_len, data, len);
+	return r;
+}

src/rsa/rsa_i31_oaep_encrypt.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 */
+size_t
+br_rsa_i31_oaep_encrypt(
+	const br_prng_class **rnd, const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_public_key *pk,
+	void *dst, size_t dst_max_len,
+	const void *src, size_t src_len)
+{
+	size_t dlen;
+
+	dlen = br_rsa_oaep_pad(rnd, dig, label, label_len,
+		pk, dst, dst_max_len, src, src_len);
+	if (dlen == 0) {
+		return 0;
+	}
+	return dlen & -(size_t)br_rsa_i31_public(dst, dlen, pk);
+}

src/rsa/rsa_i32_oaep_decrypt.c

@@ -0,0 +1,41 @@
+/*
+ * 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_oaep_decrypt(const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_private_key *sk, void *data, size_t *len)
+{
+	uint32_t r;
+
+	if (*len != ((sk->n_bitlen + 7) >> 3)) {
+		return 0;
+	}
+	r = br_rsa_i32_private(data, sk);
+	r &= br_rsa_oaep_unpad(dig, label, label_len, data, len);
+	return r;
+}

src/rsa/rsa_i32_oaep_encrypt.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 */
+size_t
+br_rsa_i32_oaep_encrypt(
+	const br_prng_class **rnd, const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_public_key *pk,
+	void *dst, size_t dst_max_len,
+	const void *src, size_t src_len)
+{
+	size_t dlen;
+
+	dlen = br_rsa_oaep_pad(rnd, dig, label, label_len,
+		pk, dst, dst_max_len, src, src_len);
+	if (dlen == 0) {
+		return 0;
+	}
+	return dlen & -(size_t)br_rsa_i32_public(dst, dlen, pk);
+}

src/rsa/rsa_i62_oaep_decrypt.c

@@ -0,0 +1,61 @@
+/*
+ * 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_oaep_decrypt(const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_private_key *sk, void *data, size_t *len)
+{
+	uint32_t r;
+
+	if (*len != ((sk->n_bitlen + 7) >> 3)) {
+		return 0;
+	}
+	r = br_rsa_i62_private(data, sk);
+	r &= br_rsa_oaep_unpad(dig, label, label_len, data, len);
+	return r;
+}
+
+/* see bearssl_rsa.h */
+br_rsa_oaep_decrypt
+br_rsa_i62_oaep_decrypt_get(void)
+{
+	return &br_rsa_i62_oaep_decrypt;
+}
+
+#else
+
+/* see bearssl_rsa.h */
+br_rsa_oaep_decrypt
+br_rsa_i62_oaep_decrypt_get(void)
+{
+	return 0;
+}
+
+#endif

src/rsa/rsa_i62_oaep_encrypt.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 */
+size_t
+br_rsa_i62_oaep_encrypt(
+	const br_prng_class **rnd, const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_public_key *pk,
+	void *dst, size_t dst_max_len,
+	const void *src, size_t src_len)
+{
+	size_t dlen;
+
+	dlen = br_rsa_oaep_pad(rnd, dig, label, label_len,
+		pk, dst, dst_max_len, src, src_len);
+	if (dlen == 0) {
+		return 0;
+	}
+	return dlen & -(size_t)br_rsa_i62_public(dst, dlen, pk);
+}
+
+/* see bearssl_rsa.h */
+br_rsa_oaep_encrypt
+br_rsa_i62_oaep_encrypt_get(void)
+{
+	return &br_rsa_i62_oaep_encrypt;
+}
+
+#else
+
+/* see bearssl_rsa.h */
+br_rsa_oaep_encrypt
+br_rsa_i62_oaep_encrypt_get(void)
+{
+	return 0;
+}
+
+#endif

src/rsa/rsa_oaep_pad.c

@@ -0,0 +1,112 @@
+/*
+ * 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"
+
+/*
+ * Hash some data. This is put as a separate function so that stack
+ * allocation of the hash function context is done only for the duration
+ * of the hash.
+ */
+static void
+hash_data(const br_hash_class *dig, void *dst, const void *src, size_t len)
+{
+	br_hash_compat_context hc;
+
+	hc.vtable = dig;
+	dig->init(&hc.vtable);
+	dig->update(&hc.vtable, src, len);
+	dig->out(&hc.vtable, dst);
+}
+
+/* see inner.h */
+size_t
+br_rsa_oaep_pad(const br_prng_class **rnd, const br_hash_class *dig,
+	const void *label, size_t label_len,
+	const br_rsa_public_key *pk,
+	void *dst, size_t dst_max_len,
+	const void *src, size_t src_len)
+{
+	size_t k, hlen;
+	unsigned char *buf;
+
+	hlen = br_digest_size(dig);
+
+	/*
+	 * Compute actual modulus length (in bytes).
+	 */
+	k = pk->nlen;
+	while (k > 0 && pk->n[k - 1] == 0) {
+		k --;
+	}
+
+	/*
+	 * An error is reported if:
+	 *  - the modulus is too short;
+	 *  - the source message length is too long;
+	 *  - the destination buffer is too short.
+	 */
+	if (k < ((hlen << 1) + 2)
+		|| src_len > (k - (hlen << 1) - 2)
+		|| dst_max_len < k)
+	{
+		return 0;
+	}
+
+	/*
+	 * Apply padding. At this point, things cannot fail.
+	 */
+	buf = dst;
+
+	/*
+	 * Assemble: DB = lHash || PS || 0x01 || M
+	 * We first place the source message M with memmove(), so that
+	 * overlaps between source and destination buffers are supported.
+	 */
+	memmove(buf + k - src_len, src, src_len);
+	hash_data(dig, buf + 1 + hlen, label, label_len);
+	memset(buf + 1 + (hlen << 1), 0, k - src_len - (hlen << 1) - 2);
+	buf[k - src_len - 1] = 0x01;
+
+	/*
+	 * Make the random seed.
+	 */
+	(*rnd)->generate(rnd, buf + 1, hlen);
+
+	/*
+	 * Mask DB with the mask generated from the seed.
+	 */
+	br_mgf1_xor(buf + 1 + hlen, k - hlen - 1, dig, buf + 1, hlen);
+
+	/*
+	 * Mask the seed with the mask generated from the masked DB.
+	 */
+	br_mgf1_xor(buf + 1, hlen, dig, buf + 1 + hlen, k - hlen - 1);
+
+	/*
+	 * Padding result: EM = 0x00 || maskedSeed || maskedDB.
+	 */
+	buf[0] = 0x00;
+	return k;
+}

src/rsa/rsa_oaep_unpad.c

@@ -0,0 +1,145 @@
+/*
+ * 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"
+
+/*
+ * Hash some data and XOR the result into the provided buffer. This is put
+ * as a separate function so that stack allocation of the hash function
+ * context is done only for the duration of the hash.
+ */
+static void
+xor_hash_data(const br_hash_class *dig, void *dst, const void *src, size_t len)
+{
+	br_hash_compat_context hc;
+	unsigned char tmp[64];
+	unsigned char *buf;
+	size_t u, hlen;
+
+	hc.vtable = dig;
+	dig->init(&hc.vtable);
+	dig->update(&hc.vtable, src, len);
+	dig->out(&hc.vtable, tmp);
+	buf = dst;
+	hlen = br_digest_size(dig);
+	for (u = 0; u < hlen; u ++) {
+		buf[u] ^= tmp[u];
+	}
+}
+
+/* see inner.h */
+uint32_t
+br_rsa_oaep_unpad(const br_hash_class *dig,
+	const void *label, size_t label_len,
+	void *data, size_t *len)
+{
+	size_t u, k, hlen;
+	unsigned char *buf;
+	uint32_t r, s, zlen;
+
+	hlen = br_digest_size(dig);
+	k = *len;
+	buf = data;
+
+	/*
+	 * There must be room for the padding.
+	 */
+	if (k < ((hlen << 1) + 2)) {
+		return 0;
+	}
+
+	/*
+	 * Unmask the seed, then the DB value.
+	 */
+	br_mgf1_xor(buf + 1, hlen, dig, buf + 1 + hlen, k - hlen - 1);
+	br_mgf1_xor(buf + 1 + hlen, k - hlen - 1, dig, buf + 1, hlen);
+
+	/*
+	 * Hash the label and XOR it with the value in the array; if
+	 * they are equal then these should yield only zeros.
+	 */
+	xor_hash_data(dig, buf + 1 + hlen, label, label_len);
+
+	/*
+	 * At that point, if the padding was correct, when we should
+	 * have: 0x00 || seed || 0x00 ... 0x00 0x01 || M
+	 * Padding is valid as long as:
+	 *  - There is at least hlen+1 leading bytes of value 0x00.
+	 *  - There is at least one non-zero byte.
+	 *  - The first (leftmost) non-zero byte has value 0x01.
+	 *
+	 * Ultimately, we may leak the resulting message length, i.e.
+	 * the position of the byte of value 0x01, but we must take care
+	 * to do so only if the number of zero bytes has been verified
+	 * to be at least hlen+1.
+	 *
+	 * The loop below counts the number of bytes of value 0x00, and
+	 * checks that the next byte has value 0x01, in constant-time.
+	 *
+	 *  - If the initial byte (before the seed) is not 0x00, then
+	 *    r and s are set to 0, and stay there.
+	 *  - Value r is 1 until the first non-zero byte is reached
+	 *    (after the seed); it switches to 0 at that point.
+	 *  - Value s is set to 1 if and only if the data encountered
+	 *    at the time of the transition of r from 1 to 0 has value
+	 *    exactly 0x01.
+	 *  - Value zlen counts the number of leading bytes of value zero
+	 *    (after the seed).
+	 */
+	r = 1 - ((buf[0] + 0xFF) >> 8);
+	s = 0;
+	zlen = 0;
+	for (u = hlen + 1; u < k; u ++) {
+		uint32_t w, nz;
+
+		w = buf[u];
+
+		/*
+		 * nz == 1 only for the first non-zero byte.
+		 */
+		nz = r & ((w + 0xFF) >> 8);
+		s |= nz & EQ(w, 0x01);
+		r &= NOT(nz);
+		zlen += r;
+	}
+
+	/*
+	 * Padding is correct only if s == 1, _and_ zlen >= hlen.
+	 */
+	s &= GE(zlen, (uint32_t)hlen);
+
+	/*
+	 * At that point, padding was verified, and we are now allowed
+	 * to make conditional jumps.
+	 */
+	if (s) {
+		size_t plen;
+
+		plen = 2 + hlen + zlen;
+		k -= plen;
+		memmove(data, data + plen, k);
+		*len = k;
+	}
+	return s;
+}