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Constant time raw key by Sc00bz · Pull Request #596 · sqlcipher/sqlcipher · GitHub

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Constant time raw key #596

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Constant time raw key #596

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106 changes: 59 additions & 47 deletions src/sqlcipher.c
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Original file line number Diff line number Diff line change
Expand Up @@ -333,10 +333,16 @@ static void *sqlcipher_internal_malloc(sqlite_uint64);
/*
** Simple shared routines for converting hex char strings to binary data
*/
static int cipher_hex2int(char c) {
return (c>='0' && c<='9') ? (c)-'0' :
(c>='A' && c<='F') ? (c)-'A'+10 :
(c>='a' && c<='f') ? (c)-'a'+10 : 0;
static int cipher_hex2int(unsigned char c) {
volatile int ch = c;
volatile int ret = -1;
/* if (ch > '0'-1 && ch < '9'+1) ret += ch - '0' + 1; */
ret += (((('0'-1) - ch) & (ch - ('9'+1))) >> 8) & (ch + (1 - '0'));
/* case insensitive */
ch |= 0x20;
/* if (ch > 'a'-1 && ch < 'f'+1) ret += ch - 'a' + 10 + 1; */
ret += (((('a'-1) - ch) & (ch - ('f'+1))) >> 8) & (ch + (10 + 1 - 'a'));
return ret;
}

static void cipher_hex2bin(const unsigned char *hex, int sz, unsigned char *out){
Expand All @@ -346,24 +352,28 @@ static void cipher_hex2bin(const unsigned char *hex, int sz, unsigned char *out)
}
}

static void cipher_bin2hex(const unsigned char* in, int sz, char *out) {
int i;
for(i=0; i < sz; i++) {
sqlite3_snprintf(3, out + (i*2), "%02x", in[i]);
}
static char cipher_int2hex(unsigned int src) {
volatile unsigned int ret = src + '0';
/* if (in > '9') in += 'a' - '9' - 1; */
ret += (('9' - ret) >> 8) & ('a' - '9' - 1);
return (char) ret;
}

static int cipher_isHex(const unsigned char *hex, int sz){
static void cipher_bin2hex(const unsigned char* in, int sz, char *out) {
int i;
for(i = 0; i < sz; i++) {
unsigned char c = hex[i];
if ((c < '0' || c > '9') &&
(c < 'A' || c > 'F') &&
(c < 'a' || c > 'f')) {
return 0;
}
unsigned char ch = in[i];
out[i*2+0] = cipher_int2hex(ch >> 4);
out[i*2+1] = cipher_int2hex(ch & 0xf);
}
return 1;
}

static int cipher_is_invalid_hex(const unsigned char *hex, int sz) {
volatile int i, ret = 0;
for(i = 0; i < sz; i++) {
ret |= cipher_hex2int(hex[i]);
}
return ret >> 8;
}

sqlite3_mutex* sqlcipher_mutex(int mutex) {
Expand Down Expand Up @@ -1745,7 +1755,8 @@ static int sqlcipher_page_cipher(codec_ctx *ctx, int for_ctx, Pgno pgno, int mod
* returns SQLITE_ERROR if the key could't be derived (for instance if pass is NULL or pass_sz is 0)
*/
static int sqlcipher_cipher_ctx_key_derive(codec_ctx *ctx, cipher_ctx *c_ctx) {
int rc, raw_key_sz = 0, raw_salt_sz = 0, blob_format = 0, derive_hmac_key = 1;
int rc, raw_key_sz = 0, raw_salt_sz = 0, derive_hmac_key = 1;
volatile int not_blob_format = 1;

sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: ctx->kdf_salt_sz=%d ctx->kdf_iter=%d ctx->fast_kdf_iter=%d ctx->key_sz=%d",
__func__, ctx->kdf_salt_sz, ctx->kdf_iter, ctx->fast_kdf_iter, ctx->key_sz);
Expand All @@ -1766,40 +1777,41 @@ static int sqlcipher_cipher_ctx_key_derive(codec_ctx *ctx, cipher_ctx *c_ctx) {

/* raw hey hex encoded is 2x long */
raw_key_sz = ctx->key_sz * 2;
raw_salt_sz = ctx->kdf_salt_sz *2;
raw_salt_sz = ctx->kdf_salt_sz * 2;

/* raw key must be BLOB formatted:
* 1. greater than or equal to 5 characters long
* 1. a valid size
* 2. starting with x'
* 3. ending with '
* 4. length of contents between the x' and ' must be a power of 2
* 5. contents must be hex */
blob_format =
c_ctx->pass_sz >= 5
&& sqlite3StrNICmp((const char *)c_ctx->pass ,"x'", 2) == 0
&& c_ctx->pass[c_ctx->pass_sz - 1] == '\''
&& (c_ctx->pass_sz - 3) % 2 == 0
&& cipher_isHex(c_ctx->pass + 2, c_ctx->pass_sz - 3);

if(blob_format && c_ctx->pass_sz == raw_key_sz + 3) {
/* option 1 - raw key consisting of only the encryption key */
* 4. contents must be hex */
if(c_ctx->pass_sz == raw_key_sz + 3 ||
c_ctx->pass_sz == raw_key_sz + raw_salt_sz + 3 ||
c_ctx->pass_sz == raw_key_sz + raw_key_sz + raw_salt_sz + 3) {
not_blob_format = 'x' ^ (c_ctx->pass[0] | 0x20); /* case insensitive */
not_blob_format |= '\'' ^ c_ctx->pass[1];
not_blob_format |= cipher_is_invalid_hex(c_ctx->pass + 2, c_ctx->pass_sz - 3);
not_blob_format |= '\'' ^ c_ctx->pass[c_ctx->pass_sz - 1];
}

if(not_blob_format == 0) {
const unsigned char *z = c_ctx->pass + 2; /* adjust lead offset of x' */
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: using raw key only", __func__);
cipher_hex2bin(z, raw_key_sz, c_ctx->key);
} else if(blob_format && c_ctx->pass_sz == raw_key_sz + raw_salt_sz + 3) {
/* option 2 - raw key consisting of the encryption key and salt */
const unsigned char *z = c_ctx->pass + 2;
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: using raw key and salt", __func__);
cipher_hex2bin(z, raw_key_sz, c_ctx->key);
cipher_hex2bin(z + raw_key_sz, raw_salt_sz, ctx->kdf_salt);
} else if(blob_format && c_ctx->pass_sz == raw_key_sz + raw_key_sz + raw_salt_sz + 3) {
/* option 3 - raw key consisting of the encryption key, then hmac key, then salt */
const unsigned char *z = c_ctx->pass + 2;
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: using raw key, hmac key, and salt", __func__);
cipher_hex2bin(z, raw_key_sz, c_ctx->key);
cipher_hex2bin(z + raw_key_sz, raw_key_sz, c_ctx->hmac_key);
cipher_hex2bin(z + raw_key_sz + raw_key_sz, raw_salt_sz, ctx->kdf_salt);
derive_hmac_key = 0;
if(c_ctx->pass_sz == raw_key_sz + 3) {
/* option 1 - raw key consisting of only the encryption key */
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: using raw key only", __func__);
cipher_hex2bin(z, raw_key_sz, c_ctx->key);
} else if(c_ctx->pass_sz == raw_key_sz + raw_salt_sz + 3) {
/* option 2 - raw key consisting of the encryption key and salt */
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: using raw key and salt", __func__);
cipher_hex2bin(z, raw_key_sz, c_ctx->key);
cipher_hex2bin(z + raw_key_sz, raw_salt_sz, ctx->kdf_salt);
} else {
/* option 3 - raw key consisting of the encryption key, then hmac key, then salt */
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: using raw key, hmac key, and salt", __func__);
cipher_hex2bin(z, raw_key_sz, c_ctx->key);
cipher_hex2bin(z + raw_key_sz, raw_key_sz, c_ctx->hmac_key);
cipher_hex2bin(z + raw_key_sz + raw_key_sz, raw_salt_sz, ctx->kdf_salt);
derive_hmac_key = 0;
}
} else {
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "%s: deriving key using PBKDF2 with %d iterations", __func__, ctx->kdf_iter);
if((rc = ctx->provider->kdf(ctx->provider_ctx, ctx->kdf_algorithm, c_ctx->pass, c_ctx->pass_sz,
Expand Down
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