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Diffstat (limited to 'libmincrypt/rsa.c')
| -rw-r--r-- | libmincrypt/rsa.c | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/libmincrypt/rsa.c b/libmincrypt/rsa.c new file mode 100644 index 000000000..9061b3ae3 --- /dev/null +++ b/libmincrypt/rsa.c @@ -0,0 +1,308 @@ +/* rsa.c +** +** Copyright 2012, The Android Open Source Project +** +** Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions are met: +** * Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** * Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in the +** documentation and/or other materials provided with the distribution. +** * Neither the name of Google Inc. nor the names of its contributors may +** be used to endorse or promote products derived from this software +** without specific prior written permission. +** +** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR +** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF +** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO +** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, +** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; +** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, +** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR +** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF +** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +*/ + +#include "mincrypt/rsa.h" +#include "mincrypt/sha.h" +#include "mincrypt/sha256.h" + +// a[] -= mod +static void subM(const RSAPublicKey* key, + uint32_t* a) { + int64_t A = 0; + int i; + for (i = 0; i < key->len; ++i) { + A += (uint64_t)a[i] - key->n[i]; + a[i] = (uint32_t)A; + A >>= 32; + } +} + +// return a[] >= mod +static int geM(const RSAPublicKey* key, + const uint32_t* a) { + int i; + for (i = key->len; i;) { + --i; + if (a[i] < key->n[i]) return 0; + if (a[i] > key->n[i]) return 1; + } + return 1; // equal +} + +// montgomery c[] += a * b[] / R % mod +static void montMulAdd(const RSAPublicKey* key, + uint32_t* c, + const uint32_t a, + const uint32_t* b) { + uint64_t A = (uint64_t)a * b[0] + c[0]; + uint32_t d0 = (uint32_t)A * key->n0inv; + uint64_t B = (uint64_t)d0 * key->n[0] + (uint32_t)A; + int i; + + for (i = 1; i < key->len; ++i) { + A = (A >> 32) + (uint64_t)a * b[i] + c[i]; + B = (B >> 32) + (uint64_t)d0 * key->n[i] + (uint32_t)A; + c[i - 1] = (uint32_t)B; + } + + A = (A >> 32) + (B >> 32); + + c[i - 1] = (uint32_t)A; + + if (A >> 32) { + subM(key, c); + } +} + +// montgomery c[] = a[] * b[] / R % mod +static void montMul(const RSAPublicKey* key, + uint32_t* c, + const uint32_t* a, + const uint32_t* b) { + int i; + for (i = 0; i < key->len; ++i) { + c[i] = 0; + } + for (i = 0; i < key->len; ++i) { + montMulAdd(key, c, a[i], b); + } +} + +// In-place public exponentiation. +// Input and output big-endian byte array in inout. +static void modpow(const RSAPublicKey* key, + uint8_t* inout) { + uint32_t a[RSANUMWORDS]; + uint32_t aR[RSANUMWORDS]; + uint32_t aaR[RSANUMWORDS]; + uint32_t* aaa = 0; + int i; + + // Convert from big endian byte array to little endian word array. + for (i = 0; i < key->len; ++i) { + uint32_t tmp = + (inout[((key->len - 1 - i) * 4) + 0] << 24) | + (inout[((key->len - 1 - i) * 4) + 1] << 16) | + (inout[((key->len - 1 - i) * 4) + 2] << 8) | + (inout[((key->len - 1 - i) * 4) + 3] << 0); + a[i] = tmp; + } + + if (key->exponent == 65537) { + aaa = aaR; // Re-use location. + montMul(key, aR, a, key->rr); // aR = a * RR / R mod M + for (i = 0; i < 16; i += 2) { + montMul(key, aaR, aR, aR); // aaR = aR * aR / R mod M + montMul(key, aR, aaR, aaR); // aR = aaR * aaR / R mod M + } + montMul(key, aaa, aR, a); // aaa = aR * a / R mod M + } else if (key->exponent == 3) { + aaa = aR; // Re-use location. + montMul(key, aR, a, key->rr); /* aR = a * RR / R mod M */ + montMul(key, aaR, aR, aR); /* aaR = aR * aR / R mod M */ + montMul(key, aaa, aaR, a); /* aaa = aaR * a / R mod M */ + } + + // Make sure aaa < mod; aaa is at most 1x mod too large. + if (geM(key, aaa)) { + subM(key, aaa); + } + + // Convert to bigendian byte array + for (i = key->len - 1; i >= 0; --i) { + uint32_t tmp = aaa[i]; + *inout++ = tmp >> 24; + *inout++ = tmp >> 16; + *inout++ = tmp >> 8; + *inout++ = tmp >> 0; + } +} + +// Expected PKCS1.5 signature padding bytes, for a keytool RSA signature. +// Has the 0-length optional parameter encoded in the ASN1 (as opposed to the +// other flavor which omits the optional parameter entirely). This code does not +// accept signatures without the optional parameter. + +/* +static const uint8_t sha_padding[RSANUMBYTES] = { + 0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x21, 0x30, + 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, + 0x05, 0x00, 0x04, 0x14, + + // 20 bytes of hash go here. + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 +}; +*/ + +// SHA-1 of PKCS1.5 signature sha_padding for 2048 bit, as above. +// At the location of the bytes of the hash all 00 are hashed. +static const uint8_t kExpectedPadShaRsa2048[SHA_DIGEST_SIZE] = { + 0xdc, 0xbd, 0xbe, 0x42, 0xd5, 0xf5, 0xa7, 0x2e, + 0x6e, 0xfc, 0xf5, 0x5d, 0xaf, 0x9d, 0xea, 0x68, + 0x7c, 0xfb, 0xf1, 0x67 +}; + +/* +static const uint8_t sha256_padding[RSANUMBYTES] = { + 0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, + 0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x31, 0x30, + 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, + 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20, + + // 32 bytes of hash go here. + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, +}; +*/ + +// SHA-256 of PKCS1.5 signature sha256_padding for 2048 bit, as above. +// At the location of the bytes of the hash all 00 are hashed. +static const uint8_t kExpectedPadSha256Rsa2048[SHA256_DIGEST_SIZE] = { + 0xab, 0x28, 0x8d, 0x8a, 0xd7, 0xd9, 0x59, 0x92, + 0xba, 0xcc, 0xf8, 0x67, 0x20, 0xe1, 0x15, 0x2e, + 0x39, 0x8d, 0x80, 0x36, 0xd6, 0x6f, 0xf0, 0xfd, + 0x90, 0xe8, 0x7d, 0x8b, 0xe1, 0x7c, 0x87, 0x59, +}; + +// Verify a 2048-bit RSA PKCS1.5 signature against an expected hash. +// Both e=3 and e=65537 are supported. hash_len may be +// SHA_DIGEST_SIZE (== 20) to indicate a SHA-1 hash, or +// SHA256_DIGEST_SIZE (== 32) to indicate a SHA-256 hash. No other +// values are supported. +// +// Returns 1 on successful verification, 0 on failure. +int RSA_verify(const RSAPublicKey *key, + const uint8_t *signature, + const int len, + const uint8_t *hash, + const int hash_len) { + uint8_t buf[RSANUMBYTES]; + int i; + const uint8_t* padding_hash; + + if (key->len != RSANUMWORDS) { + return 0; // Wrong key passed in. + } + + if (len != sizeof(buf)) { + return 0; // Wrong input length. + } + + if (hash_len != SHA_DIGEST_SIZE && + hash_len != SHA256_DIGEST_SIZE) { + return 0; // Unsupported hash. + } + + if (key->exponent != 3 && key->exponent != 65537) { + return 0; // Unsupported exponent. + } + + for (i = 0; i < len; ++i) { // Copy input to local workspace. + buf[i] = signature[i]; + } + + modpow(key, buf); // In-place exponentiation. + + // Xor sha portion, so it all becomes 00 iff equal. + for (i = len - hash_len; i < len; ++i) { + buf[i] ^= *hash++; + } + + // Hash resulting buf, in-place. + switch (hash_len) { + case SHA_DIGEST_SIZE: + padding_hash = kExpectedPadShaRsa2048; + SHA_hash(buf, len, buf); + break; + case SHA256_DIGEST_SIZE: + padding_hash = kExpectedPadSha256Rsa2048; + SHA256_hash(buf, len, buf); + break; + default: + return 0; + } + + // Compare against expected hash value. + for (i = 0; i < hash_len; ++i) { + if (buf[i] != padding_hash[i]) { + return 0; + } + } + + return 1; // All checked out OK. +} |