Initial code.

src/lib/scryptenc/scryptenc.c

+/*-
+ * Copyright 2009 Colin Percival
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 THE AUTHOR OR CONTRIBUTORS 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.
+ *
+ * This file was originally written by Colin Percival as part of the Tarsnap
+ * online backup system.
+ */
+#include "scrypt_platform.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <openssl/aes.h>
+
+#include "crypto_aesctr.h"
+#include "crypto_scrypt.h"
+#include "memlimit.h"
+#include "scryptenc_cpuperf.h"
+#include "sha256.h"
+#include "sysendian.h"
+
+#include "scryptenc.h"
+
+#define ENCBLOCK 65536
+
+static int pickparams(size_t, double, double,
+    int *, uint32_t *, uint32_t *);
+static int checkparams(size_t, double, double, int, uint32_t, uint32_t);
+static int getsalt(uint8_t[32]);
+
+static int
+pickparams(size_t maxmem, double maxmemfrac, double maxtime,
+    int * logN, uint32_t * r, uint32_t * p)
+{
+        size_t memlimit;
+        double opps;
+        double opslimit;
+        double maxN, maxrp;
+        int rc;
+
+        /* Figure out how much memory to use. */
+        if (memtouse(maxmem, maxmemfrac, &memlimit))
+                return (1);
+
+        /* Figure out how fast the CPU is. */
+        if ((rc = scryptenc_cpuperf(&opps)) != 0)
+                return (rc);
+        opslimit = opps * maxtime;
+
+        /* Allow a minimum of 2^15 salsa20/8 cores. */
+        if (opslimit < 32768)
+                opslimit = 32768;
+
+        /* Fix r = 8 for now. */
+        *r = 8;
+
+        /*
+         * The memory limit requires that 128Nr <= memlimit, while the CPU
+         * limit requires that 4Nrp <= opslimit.  If opslimit < memlimit/32,
+         * opslimit imposes the stronger limit on N.
+         */
+#ifdef DEBUG
+        fprintf(stderr, "Requiring 128Nr <= %zu, 4Nrp <= %f\n",
+            memlimit, opslimit);
+#endif
+        if (opslimit < memlimit/32) {
+                /* Set p = 1 and choose N based on the CPU limit. */
+                *p = 1;
+                maxN = opslimit / (*r * 4);
+                for (*logN = 1; *logN < 63; *logN += 1) {
+                        if ((uint64_t)(1) << *logN > maxN / 2)
+                                break;
+                }
+        } else {
+                /* Set N based on the memory limit. */
+                maxN = memlimit / (*r * 128);
+                for (*logN = 1; *logN < 63; *logN += 1) {
+                        if ((uint64_t)(1) << *logN > maxN / 2)
+                                break;
+                }
+
+                /* Choose p based on the CPU limit. */
+                maxrp = (opslimit / 4) / ((uint64_t)(1) << *logN);
+                if (maxrp > 0x3fffffff)
+                        maxrp = 0x3fffffff;
+                *p = (uint32_t)(maxrp) / *r;
+        }
+
+#ifdef DEBUG
+        fprintf(stderr, "N = %zu r = %d p = %d\n",
+            (size_t)(1) << *logN, (int)(*r), (int)(*p));
+#endif
+
+        /* Success! */
+        return (0);
+}
+
+static int
+checkparams(size_t maxmem, double maxmemfrac, double maxtime,
+    int logN, uint32_t r, uint32_t p)
+{
+        size_t memlimit;
+        double opps;
+        double opslimit;
+        uint64_t N;
+        int rc;
+
+        /* Figure out the maximum amount of memory we can use. */
+        if (memtouse(maxmem, maxmemfrac, &memlimit))
+                return (1);
+
+        /* Figure out how fast the CPU is. */
+        if ((rc = scryptenc_cpuperf(&opps)) != 0)
+                return (rc);
+        opslimit = opps * maxtime;
+
+        /* Sanity-check values. */
+        if ((logN < 1) || (logN > 63))
+                return (7);
+        if ((uint64_t)(r) * (uint64_t)(p) >= 0x40000000)
+                return (7);
+
+        /* Check limits. */
+        N = (uint64_t)(1) << logN;
+        if ((memlimit / N) / r < 128)
+                return (9);
+        if ((opslimit / N) / (r * p) < 4)
+                return (10);
+
+        /* Success! */
+        return (0);
+}
+
+static int
+getsalt(uint8_t salt[32])
+{
+        int fd;
+        ssize_t lenread;
+        uint8_t * buf = salt;
+        size_t buflen = 32;
+
+        /* Open /dev/urandom. */
+        if ((fd = open("/dev/urandom", O_RDONLY)) == -1)
+                goto err0;
+
+        /* Read bytes until we have filled the buffer. */
+        while (buflen > 0) {
+                if ((lenread = read(fd, buf, buflen)) == -1)
+                        goto err1;
+
+                /* The random device should never EOF. */
+                if (lenread == 0)
+                        goto err1;
+
+                /* We're partly done. */
+                buf += lenread;
+                buflen -= lenread;
+        }
+
+        /* Close the device. */
+        while (close(fd) == -1) {
+                if (errno != EINTR)
+                        goto err0;
+        }
+
+        /* Success! */
+        return (0);
+
+err1:
+        close(fd);
+err0:
+        /* Failure! */
+        return (4);
+}
+
+static int
+scryptenc_setup(uint8_t header[96], uint8_t dk[64],
+    const uint8_t * passwd, size_t passwdlen,
+    size_t maxmem, double maxmemfrac, double maxtime)
+{
+        uint8_t salt[32];
+        uint8_t hbuf[32];
+        int logN;
+        uint64_t N;
+        uint32_t r;
+        uint32_t p;
+        SHA256_CTX ctx;
+        uint8_t * key_hmac = &dk[32];
+        HMAC_SHA256_CTX hctx;
+        int rc;
+
+        /* Pick values for N, r, p. */
+        if ((rc = pickparams(maxmem, maxmemfrac, maxtime,
+            &logN, &r, &p)) != 0)
+                return (rc);
+        N = (uint64_t)(1) << logN;
+
+        /* Get some salt. */
+        if ((rc = getsalt(salt)) != 0)
+                return (rc);
+
+        /* Generate the derived keys. */
+        if (crypto_scrypt(passwd, passwdlen, salt, 32, N, r, p, dk, 64))
+                return (3);
+
+        /* Construct the file header. */
+        memcpy(header, "scrypt", 6);
+        header[6] = 0;
+        header[7] = logN;
+        be32enc(&header[8], r);
+        be32enc(&header[12], p);
+        memcpy(&header[16], salt, 32);
+
+        /* Add header checksum. */
+        SHA256_Init(&ctx);
+        SHA256_Update(&ctx, header, 48);
+        SHA256_Final(hbuf, &ctx);
+        memcpy(&header[48], hbuf, 16);
+
+        /* Add header signature (used for verifying password). */
+        HMAC_SHA256_Init(&hctx, key_hmac, 32);
+        HMAC_SHA256_Update(&hctx, header, 64);
+        HMAC_SHA256_Final(hbuf, &hctx);
+        memcpy(&header[64], hbuf, 32);
+
+        /* Success! */
+        return (0);
+}
+
+static int
+scryptdec_setup(const uint8_t header[96], uint8_t dk[64],
+    const uint8_t * passwd, size_t passwdlen,
+    size_t maxmem, double maxmemfrac, double maxtime)
+{
+        uint8_t salt[32];
+        uint8_t hbuf[32];
+        int logN;
+        uint32_t r;
+        uint32_t p;
+        uint64_t N;
+        SHA256_CTX ctx;
+        uint8_t * key_hmac = &dk[32];
+        HMAC_SHA256_CTX hctx;
+        int rc;
+
+        /* Parse N, r, p, salt. */
+        logN = header[7];
+        r = be32dec(&header[8]);
+        p = be32dec(&header[12]);
+        memcpy(salt, &header[16], 32);
+
+        /* Verify header checksum. */
+        SHA256_Init(&ctx);
+        SHA256_Update(&ctx, header, 48);
+        SHA256_Final(hbuf, &ctx);
+        if (memcmp(&header[48], hbuf, 16))
+                return (7);
+
+        /*
+         * Check whether the provided parameters are valid and whether the
+         * key derivation function can be computed within the allowed memory
+         * and CPU time.
+         */
+        if ((rc = checkparams(maxmem, maxmemfrac, maxtime, logN, r, p)) != 0)
+                return (rc);
+
+        /* Compute the derived keys. */
+        N = (uint64_t)(1) << logN;
+        if (crypto_scrypt(passwd, passwdlen, salt, 32, N, r, p, dk, 64))
+                return (3);
+
+        /* Check header signature (i.e., verify password). */
+        HMAC_SHA256_Init(&hctx, key_hmac, 32);
+        HMAC_SHA256_Update(&hctx, header, 64);
+        HMAC_SHA256_Final(hbuf, &hctx);
+        if (memcmp(hbuf, &header[64], 32))
+                return (11);
+
+        /* Success! */
+        return (0);
+}
+
+/**
+ * scryptenc_buf(inbuf, inbuflen, outbuf, passwd, passwdlen,
+ *     maxmem, maxmemfrac, maxtime):
+ * Encrypt inbuflen bytes from inbuf, writing the resulting inbuflen + 128
+ * bytes to outbuf.
+ */
+int
+scryptenc_buf(const uint8_t * inbuf, size_t inbuflen, uint8_t * outbuf,
+    const uint8_t * passwd, size_t passwdlen,
+    size_t maxmem, double maxmemfrac, double maxtime)
+{
+        uint8_t dk[64];
+        uint8_t hbuf[32];
+        uint8_t header[96];
+        uint8_t * key_enc = dk;
+        uint8_t * key_hmac = &dk[32];
+        int rc;
+        HMAC_SHA256_CTX hctx;
+        AES_KEY key_enc_exp;
+        struct crypto_aesctr * AES;
+
+        /* Generate the header and derived key. */
+        if ((rc = scryptenc_setup(header, dk, passwd, passwdlen,
+            maxmem, maxmemfrac, maxtime)) != 0)
+                return (rc);
+
+        /* Copy header into output buffer. */
+        memcpy(outbuf, header, 96);
+
+        /* Encrypt data. */
+        if (AES_set_encrypt_key(key_enc, 256, &key_enc_exp))
+                return (5);
+        if ((AES = crypto_aesctr_init(&key_enc_exp, 0)) == NULL)
+                return (6);
+        crypto_aesctr_stream(AES, inbuf, &outbuf[96], inbuflen);
+        crypto_aesctr_free(AES);
+
+        /* Add signature. */
+        HMAC_SHA256_Init(&hctx, key_hmac, 32);
+        HMAC_SHA256_Update(&hctx, outbuf, 96 + inbuflen);
+        HMAC_SHA256_Final(hbuf, &hctx);
+        memcpy(&outbuf[96 + inbuflen], hbuf, 32);
+
+        /* Zero sensitive data. */
+        memset(dk, 0, 64);
+        memset(&key_enc_exp, 0, sizeof(AES_KEY));
+
+        /* Success! */
+        return (0);
+}
+
+/**
+ * scryptdec_buf(inbuf, inbuflen, outbuf, outlen, passwd, passwdlen,
+ *     maxmem, maxmemfrac, maxtime):
+ * Decrypt inbuflen bytes fro inbuf, writing the result into outbuf and the
+ * decrypted data length to outlen.  The allocated length of outbuf must
+ * be at least inbuflen.
+ */
+int
+scryptdec_buf(const uint8_t * inbuf, size_t inbuflen, uint8_t * outbuf,
+    size_t * outlen, const uint8_t * passwd, size_t passwdlen,
+    size_t maxmem, double maxmemfrac, double maxtime)
+{
+        uint8_t hbuf[32];
+        uint8_t dk[64];
+        uint8_t * key_enc = dk;
+        uint8_t * key_hmac = &dk[32];
+        int rc;
+        HMAC_SHA256_CTX hctx;
+        AES_KEY key_enc_exp;
+        struct crypto_aesctr * AES;
+
+        /*
+         * All versions of the scrypt format will start with "scrypt" and
+         * have at least 7 bytes of header.
+         */
+        if ((inbuflen < 7) || (memcmp(inbuf, "scrypt", 6) != 0))
+                return (7);
+
+        /* Check the format. */
+        if (inbuf[6] != 0)
+                return (8);
+
+        /* We must have at least 128 bytes. */
+        if (inbuflen < 128)
+                return (7);
+
+        /* Parse the header and generate derived keys. */
+        if ((rc = scryptdec_setup(inbuf, dk, passwd, passwdlen,
+            maxmem, maxmemfrac, maxtime)) != 0)
+                return (rc);
+
+        /* Decrypt data. */
+        if (AES_set_encrypt_key(key_enc, 256, &key_enc_exp))
+                return (5);
+        if ((AES = crypto_aesctr_init(&key_enc_exp, 0)) == NULL)
+                return (6);
+        crypto_aesctr_stream(AES, &inbuf[96], outbuf, inbuflen - 128);
+        crypto_aesctr_free(AES);
+        *outlen = inbuflen - 128;
+
+        /* Verify signature. */
+        HMAC_SHA256_Init(&hctx, key_hmac, 32);
+        HMAC_SHA256_Update(&hctx, inbuf, inbuflen - 32);
+        HMAC_SHA256_Final(hbuf, &hctx);
+        if (memcmp(hbuf, &inbuf[inbuflen - 32], 32))
+                return (7);
+
+        /* Zero sensitive data. */
+        memset(dk, 0, 64);
+        memset(&key_enc_exp, 0, sizeof(AES_KEY));
+
+        /* Success! */
+        return (0);
+}
+
+/**
+ * scryptenc_file(infile, outfile, passwd, passwdlen,
+ *     maxmem, maxmemfrac, maxtime):
+ * Read a stream from infile and encrypt it, writing the resulting stream to
+ * outfile.
+ */
+int
+scryptenc_file(FILE * infile, FILE * outfile,
+    const uint8_t * passwd, size_t passwdlen,
+    size_t maxmem, double maxmemfrac, double maxtime)
+{
+        uint8_t buf[ENCBLOCK];
+        uint8_t dk[64];
+        uint8_t hbuf[32];
+        uint8_t header[96];
+        uint8_t * key_enc = dk;
+        uint8_t * key_hmac = &dk[32];
+        size_t readlen;
+        HMAC_SHA256_CTX hctx;
+        AES_KEY key_enc_exp;
+        struct crypto_aesctr * AES;
+        int rc;
+
+        /* Generate the header and derived key. */
+        if ((rc = scryptenc_setup(header, dk, passwd, passwdlen,
+            maxmem, maxmemfrac, maxtime)) != 0)
+                return (rc);
+
+        /* Hash and write the header. */
+        HMAC_SHA256_Init(&hctx, key_hmac, 32);
+        HMAC_SHA256_Update(&hctx, header, 96);
+        if (fwrite(header, 96, 1, outfile) != 1)
+                return (12);
+
+        /*
+         * Read blocks of data, encrypt them, and write them out; hash the
+         * data as it is produced.
+         */
+        if (AES_set_encrypt_key(key_enc, 256, &key_enc_exp))
+                return (5);
+        if ((AES = crypto_aesctr_init(&key_enc_exp, 0)) == NULL)
+                return (6);
+        do {
+                if ((readlen = fread(buf, 1, ENCBLOCK, infile)) == 0)
+                        break;
+                crypto_aesctr_stream(AES, buf, buf, readlen);
+                HMAC_SHA256_Update(&hctx, buf, readlen);
+                if (fwrite(buf, 1, readlen, outfile) < readlen)
+                        return (12);
+        } while (1);
+        crypto_aesctr_free(AES);
+
+        /* Did we exit the loop due to a read error? */
+        if (ferror(infile))
+                return (13);
+
+        /* Compute the final HMAC and output it. */
+        HMAC_SHA256_Final(hbuf, &hctx);
+        if (fwrite(hbuf, 32, 1, outfile) != 1)
+                return (12);
+
+        /* Zero sensitive data. */
+        memset(dk, 0, 64);
+        memset(&key_enc_exp, 0, sizeof(AES_KEY));
+
+        /* Success! */
+        return (0);
+}
+
+/**
+ * scryptdec_file(infile, outfile, passwd, passwdlen,
+ *     maxmem, maxmemfrac, maxtime):
+ * Read a stream from infile and decrypt it, writing the resulting stream to
+ * outfile.
+ */
+int
+scryptdec_file(FILE * infile, FILE * outfile,
+    const uint8_t * passwd, size_t passwdlen,
+    size_t maxmem, double maxmemfrac, double maxtime)
+{
+        uint8_t buf[ENCBLOCK + 32];
+        uint8_t header[96];
+        uint8_t hbuf[32];
+        uint8_t dk[64];
+        uint8_t * key_enc = dk;
+        uint8_t * key_hmac = &dk[32];
+        size_t buflen = 0;
+        size_t readlen;
+        HMAC_SHA256_CTX hctx;
+        AES_KEY key_enc_exp;
+        struct crypto_aesctr * AES;
+        int rc;
+
+        /*
+         * Read the first 7 bytes of the file; all future version of scrypt
+         * are guaranteed to have at least 7 bytes of header.
+         */
+        if (fread(header, 7, 1, infile) < 1) {
+                if (ferror(infile))
+                        return (13);
+                else
+                        return (7);
+        }
+
+        /* Do we have the right magic? */
+        if (memcmp(header, "scrypt", 6))
+                return (7);
+        if (header[6] != 0)
+                return (8);
+
+        /*
+         * Read another 89 bytes of the file; version 0 of the srypt file
+         * format has a 96-byte header.
+         */
+        if (fread(&header[7], 89, 1, infile) < 1) {
+                if (ferror(infile))
+                        return (13);
+                else
+                        return (7);
+        }
+
+        /* Parse the header and generate derived keys. */
+        if ((rc = scryptdec_setup(header, dk, passwd, passwdlen,
+            maxmem, maxmemfrac, maxtime)) != 0)
+                return (rc);
+
+        /* Start hashing with the header. */
+        HMAC_SHA256_Init(&hctx, key_hmac, 32);
+        HMAC_SHA256_Update(&hctx, header, 96);
+
+        /*
+         * We don't know how long the encrypted data block is (we can't know,
+         * since data can be streamed into 'scrypt enc') so we need to read
+         * data and decrypt all of it except the final 32 bytes, then check
+         * if that final 32 bytes is the correct signature.
+         */
+        if (AES_set_encrypt_key(key_enc, 256, &key_enc_exp))
+                return (5);
+        if ((AES = crypto_aesctr_init(&key_enc_exp, 0)) == NULL)
+                return (6);
+        do {
+                /* Read data until we have more than 32 bytes of it. */
+                if ((readlen = fread(&buf[buflen], 1,
+                    ENCBLOCK + 32 - buflen, infile)) == 0)
+                        break;
+                buflen += readlen;
+                if (buflen <= 32)
+                        continue;
+
+                /*
+                 * Decrypt, hash, and output everything except the last 32
+                 * bytes out of what we have in our buffer.
+                 */
+                HMAC_SHA256_Update(&hctx, buf, buflen - 32);
+                crypto_aesctr_stream(AES, buf, buf, buflen - 32);
+                if (fwrite(buf, 1, buflen - 32, outfile) < buflen - 32)
+                        return (12);
+
+                /* Move the last 32 bytes to the start of the buffer. */
+                memmove(buf, &buf[buflen - 32], 32);
+                buflen = 32;
+        } while (1);
+        crypto_aesctr_free(AES);
+
+        /* Did we exit the loop due to a read error? */
+        if (ferror(infile))
+                return (13);
+
+        /* Did we read enough data that we *might* have a valid signature? */
+        if (buflen < 32)
+                return (7);
+
+        /* Verify signature. */
+        HMAC_SHA256_Final(hbuf, &hctx);
+        if (memcmp(hbuf, buf, 32))
+                return (7);
+
+        /* Zero sensitive data. */
+        memset(dk, 0, 64);
+        memset(&key_enc_exp, 0, sizeof(AES_KEY));
+
+        return (0);
+}