ASN1 module compiled by asn1c fails to decode?

Question

I'm trying to parse RSA (private) keys using asn1c. I based the asn1 module on https://www.rfc-editor.org/rfc/rfc3447 and it looks as following (i tried to only use the private and public key part):

-- ===================
--   Main structures
-- ===================

RSAPrivateKey DEFINITIONS ::= 
BEGIN
--
-- Representation of RSA private key with information for the CRT
-- algorithm.
--

RSAPublicKey ::= SEQUENCE {
    modulus           INTEGER,  -- n
    publicExponent    INTEGER   -- e 
}

RSAPrivateKey ::= SEQUENCE {
    version           Version,
    modulus           INTEGER,  -- n
    publicExponent    INTEGER,  -- e
    privateExponent   INTEGER,  -- d
    prime1            INTEGER,  -- p
    prime2            INTEGER,  -- q
    exponent1         INTEGER,  -- d mod (p-1)
    exponent2         INTEGER,  -- d mod (q-1)
    coefficient       INTEGER,  -- (inverse of q) mod p
    otherPrimeInfos   OtherPrimeInfos OPTIONAL
}

Version ::= INTEGER { two-prime(0), multi(1) }
    (CONSTRAINED BY {
        -- version must be multi if otherPrimeInfos present --
    })

OtherPrimeInfos ::= SEQUENCE SIZE(1..MAX) OF OtherPrimeInfo

OtherPrimeInfo ::= SEQUENCE {
    prime             INTEGER,  -- ri
    exponent          INTEGER,  -- di
    coefficient       INTEGER   -- ti
}

END  -- PKCS1Definitions

However when i compile the module and try to parse .der private key using the following, it ends with RC_FAIL.

RSAPrivateKey_t *rsa_p_key;
rsa_p_key= (RSAPrivateKey_t*)calloc(1, sizeof *rsa_p_key);

asn_dec_rval_t  rval = ber_decode(
    0,
    &asn_DEF_RSAPrivateKey,
    (void**)&rsa_p_key,
    buffer, // buffer containing key (unsigned char*)
    buffer_len); // buffer length (amount of read bytes)

I've been trying to find the error in asn1 module, but with no luck. Using openssl to print out the .der file, it seems to match the RSAPrivateKey. I also tested for erronous file reading, but buffer matches and binary read mode is used.

Answer 1

You need to compile with -fwide-types flag.

-fwide-types Use the wide integer types (INTEGER_t, REAL_t) instead of ma-chine’s native data types (long, double).

The problem is that most of the INTEGER fields of RSAPrivateKey contain really big numbers that not fit in long type that is being used by default.

Without -fwide-types

/* RSAPrivateKey */
typedef struct RSAPrivateKey {
    Version_t    version;
    long     modulus;
    long     publicExponent;
    long     privateExponent;

With -fwide-types

/* RSAPrivateKey */
typedef struct RSAPrivateKey {
    Version_t    version;
    INTEGER_t    modulus;
    INTEGER_t    publicExponent;
    INTEGER_t    privateExponent;

$ asn1c -fwide-types rfc3447.asn1
$ make -f converter-example.mk
$ ./converter-example -p RSAPrivateKey -iber ./temp/key.der 
<RSAPrivateKey>
    <version>0</version>
    <modulus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modulus>
    <publicExponent>65537</publicExponent>
    <privateExponent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privateExponent>
    <prime1>00:E7:38:46:89:D6:43:E5:A2:80:F7:EB:03:8B:15:B0:24:CE:9E:0F:4F:4D:1C:C5:7F:15:9B:12:05:D5:4C:20:C8:D2:9C:7C:30:3F:99:84:3A:6E:4B:BA:A0:BF:34:40:C3:30:80:D1:AE:6B:04:C6:DB:E0:FA:5F:65:14:96:0B:3B:9A:75:8E:84:C2:F5:96:98:09:09:87:2F:62:19:87:AB:BB:C7:87:67:67:07:61:5B:8B:CC:B2:19:52:74:1C:91:F7:12:F0:E5:9B:B3:3C:81:2E:F4:2A:E4:AC:56:6D:38:95:DB:18:5E:7B:4F:96:B1:E5:80:41:C2:28:AC:2A:E7</prime1>
    <prime2>00:D5:F3:BA:B4:3C:3B:B0:02:0C:E9:BA:21:CC:03:23:26:F5:0B:2B:27:B0:74:C6:E2:F8:FD:3F:CB:1F:CA:1A:B9:12:4C:B6:7E:56:D4:AB:A8:F2:8D:81:54:63:0C:0E:16:79:54:0B:7C:13:7F:E6:66:12:BD:A0:62:F3:D6:8A:AC:B5:2A:58:70:58:8C:16:94:95:97:2D:9C:2A:A8:30:3F:35:43:57:D7:79:3D:9B:EF:56:95:A0:81:24:DC:67:C5:DA:66:F0:7E:02:94:59:4C:1B:EB:AB:67:0E:B6:C3:BD:92:0B:7C:B4:8E:44:AE:32:1A:42:A1:C7:93:6A:44:B5</prime2>
    <exponent1>00:82:E3:65:72:E3:9A:FD:E4:36:D3:A0:F3:19:89:C6:73:9F:8E:F4:25:B5:06:43:7A:84:55:8B:27:48:2E:57:24:B7:AC:A3:D4:80:3C:3C:11:03:9C:D4:E1:E8:3B:01:2A:3D:4B:BE:E6:D8:68:14:D6:25:8E:35:F0:37:6E:14:9F:C1:F9:28:1B:59:6D:C2:B8:FF:EC:A7:DD:17:D0:51:EF:D2:55:C9:FD:AB:E2:0E:A7:CF:04:AA:11:11:8E:EF:19:65:DF:10:05:3A:55:85:3B:AF:C3:C2:80:3E:5A:92:6B:84:D1:49:03:3B:14:BB:BE:AA:A7:27:12:6D:09:C1:23</exponent1>
    <exponent2>6E:22:70:D1:A6:CF:F2:E2:9B:53:15:85:A0:47:5D:29:08:AB:1F:23:E7:29:B5:D7:D0:E4:4C:9A:7B:5A:C6:36:CE:BC:BE:94:7A:8E:2F:6F:60:AC:87:0E:B1:8D:DB:12:A6:92:24:F7:51:F2:5C:DF:DE:75:CE:C2:21:53:27:3F:90:62:A3:F3:F1:20:EB:DE:C0:C2:79:B0:12:25:51:F0:B7:B2:5A:DD:88:83:B6:69:95:E0:A0:26:DA:9A:BA:B0:96:A4:B6:D7:A6:EC:46:AB:6F:13:F9:BF:AB:4B:59:A7:94:2E:65:9B:6C:40:DE:8A:DC:09:C0:CD:C3:8C:C8:A1</exponent2>
    <coefficient>43:9A:41:22:B1:F4:15:A9:C7:95:FD:F7:7E:55:BC:24:16:5F:E2:9D:B0:D5:74:54:1B:F6:C9:76:C4:6A:4E:5E:6C:AE:71:E1:9A:DE:F1:26:47:B4:41:45:BD:0A:2E:E4:02:DE:AD:28:21:2D:50:59:99:DA:26:E0:90:1A:84:2B:22:46:48:CC:DB:1F:7E:9B:9B:F5:02:D8:24:6F:7E:F3:D9:30:91:1F:83:22:9A:94:C7:F4:29:B2:93:68:CB:57:BC:C5:60:96:0E:42:42:55:D2:3A:71:B5:31:78:D3:D1:2A:74:03:C2:45:A2:9A:A2:89:6F:62:63:C6:42:7B:2D</coefficient>
</RSAPrivateKey>