Created a tool using openssl crypto library. The tool can decrypt and

dump user's session key chain to stdout.

CASA/test/micasa_dump/Makefile

@@ -0,0 +1,9 @@
+CFLAGS=-fpermissive -g
+
+all: micasa-decrypt.exe
+
+micasa-decrypt.exe: main.cpp
+	g++ $(CFLAGS) $^ -o $@ -lcrypto
+
+clean:
+	rm -f micasa-decrypt.exe

CASA/test/micasa_dump/main.cpp

@@ -0,0 +1,193 @@
+#include <iostream>
+
+#include <stdio.h>
+#include <assert.h>
+#include <openssl/aes.h>
+#include <openssl/evp.h>
+#include <openssl/sha.h>
+
+using namespace std;
+
+#define AES_KEY_128 128
+#define AES_KEY_256 256
+#define AES_KEY_BYTES_128 (AES_KEY_128/8)
+#define AES_KEY_BYTES_256 (AES_KEY_256/8)
+
+int password_to_key(const string *password,
+		    const unsigned char *salt,
+		    size_t salt_len,
+		    unsigned char *key,
+		    size_t key_len)
+{
+	int rc;
+	unsigned char hash[20];
+	assert(key_len == AES_KEY_BYTES_128);
+	assert(salt_len == 64);
+
+	rc = PKCS5_PBKDF2_HMAC_SHA1(password->c_str(),
+			           password->length(),
+				   salt,
+				   salt_len,
+				   1000 /*iter*/,
+				   key_len,
+				   key);
+
+	return (rc == 1)? 0 : 1;
+}
+
+int decrypt(const unsigned char *in,
+	    unsigned char *out,
+	    size_t len,
+	    const unsigned char *key,
+	    size_t key_len,
+	    const unsigned char *IV,
+	    size_t IV_len)
+{
+	AES_KEY key_dec;
+
+	assert((key_len == AES_KEY_BYTES_128) || (key_len = AES_KEY_BYTES_256));
+	assert(IV_len == AES_KEY_BYTES_128);
+
+	assert(len % 16 == 0);
+
+	AES_set_decrypt_key(key, key_len*8, &key_dec);
+	AES_cbc_encrypt(in, out, len, &key_dec, IV, AES_DECRYPT);
+
+	return 0;
+}
+
+/* decrypt and validate checksum. in := (256 bit checksum) | (cipher text) */
+int decrypt_and_validate(const unsigned char *in,
+			 unsigned char *out,
+			 size_t *len,
+			 const unsigned char *key,
+			 size_t key_len,
+			 const unsigned char *IV,
+			 size_t IV_len) {
+	int rc, l = *len;
+	const unsigned char *hash = in, *CT = in + 32;
+	unsigned char *h, md[32];
+
+	assert(*len > 32);
+
+	rc = decrypt(CT, out, *len - 32, key, key_len, IV, IV_len);
+
+	*len = (*len - 32) - out[*len - 32 - 1];
+	bzero(out + *len, l - *len);
+	h = SHA256(out, *len, md);
+	assert(memcmp(md, hash, 32) == 0);
+
+	return rc;
+}
+
+int decrypt_and_validate_file(string file,
+			      unsigned char *out,
+			      size_t *len, 
+			      const unsigned char *key,
+			      size_t key_len)
+{
+	int rc, l, in_len = *len;
+	unsigned char IV[16], *CT;
+	FILE *fd;
+
+	/* Open the encrypted file and read contents */
+	fd = fopen(file.c_str(), "r");
+	assert(fd != NULL);
+	CT = new unsigned char[*len];
+	*len = fread((void *)CT, 1, *len, fd);
+	assert(*len < in_len);
+	fclose(fd);
+
+	/* Read the IV */
+	file.append(".IV");
+	fd = fopen(file.c_str(), "r");
+	assert(fd != NULL);
+	l = fread((void *)IV, 1, sizeof(IV), fd);
+	assert(l == sizeof(IV));
+	/* Add a check to ensure that file size is exactly 16 bytes */
+	fclose(fd);
+
+	/* Decrypt */
+	rc = decrypt_and_validate(CT, out, len, key, key_len, IV, sizeof(IV));
+
+	bzero(out + (*len), in_len - (*len));
+
+	delete [] CT;
+
+	return rc;
+}
+
+main()
+{
+	int rc;
+	size_t len;
+	FILE *fd;
+	unsigned char passcode[16], key[32];
+	string user, user_store;
+
+	cout << "User: ";
+	cin >> user;
+
+	user_store = "/home/.casa/" + user + "/";
+
+	/* Get passcode. Usually encrypted with desktop password */
+	{
+		unsigned char salt[64], passcode_dec[32], IV[16];
+		unsigned char passcode_enc[128], password_key[16];
+		string password;
+
+		/* Read salt */
+		fd = fopen((user_store + ".miCASAPCByDesktop.salt").c_str(), "r");
+		len = fread((void *)salt, 1, sizeof(salt), fd);
+		assert(len == sizeof(salt));
+		fclose(fd);
+
+		/* Read IV */
+		fd = fopen((user_store + ".miCASAPCByDesktop.IV").c_str(), "r");
+		len = fread((void *)IV, 1, sizeof(IV), fd);
+		assert(len == sizeof(IV));
+		fclose(fd);
+
+		/* Prompt user for password and convert password to key */
+		cout << "Password: ";
+		cin >> password;
+		password_to_key(&password, salt, sizeof(salt), password_key, sizeof(password_key));
+
+		/* Read encrypted passcode */
+		fd = fopen((user_store + ".miCASAPCByDesktop").c_str(), "r");
+		len = fread((void *)passcode_enc, 1, sizeof(passcode_enc), fd);
+		assert(len == sizeof(passcode_dec));
+		fclose(fd);
+
+		/* Decrypt */
+		rc = decrypt(passcode_enc, passcode_dec, len, password_key,
+			     sizeof(password_key), IV, sizeof(IV));
+		assert(rc == 0);
+
+		memcpy(passcode, passcode_dec, sizeof(passcode));
+	}
+
+	/* get secret key from .miCASAKey */
+	{
+		unsigned char plain_text[128];
+
+		len = sizeof(plain_text);
+		rc = decrypt_and_validate_file(user_store + ".miCASAKey",
+					       plain_text, &len, passcode,
+					       sizeof(passcode));
+		assert(len == sizeof(key));
+		memcpy(key, plain_text, sizeof(key));
+	}
+
+
+	/* Decrypt micasa store */
+	{
+		unsigned char plain_text[4096];
+
+		len = sizeof(plain_text);
+		rc = decrypt_and_validate_file(user_store + ".miCASA",
+					       plain_text, &len, key,
+					       sizeof(key));
+		puts(plain_text);
+	}
+}