SSCrypto not returning Base64 decode

gistfile1.m

/*
I'm using the SSCrypto framework, but I'm just using it copied into my project source
as a class.

http://septicus.com/products/opensource/

Elsewhere in the SSCrypto class, I call this with an NSString:
*/

/**
 * Set the cipher text from a base64 encoded string.
 * The cipher text will be used for decryption and verifying.
 **/
- (void)setCipherTextFromBase64String:(NSString*) s
{
    [cipherText release];
    NSData* data= [s dataUsingEncoding:NSUTF8StringEncoding];
    cipherText = [data decodeBase64]; // This returns an empty NSData object
    [cipherText retain];
}

/*
The NSString s gets the string fine, and is converted to the NSData data fine.
BUT, as noted, the [data decodeBase64] returns an empty NSData object (and again, yes,
there was data actually in it before I called this).

This is the method called in question. SSCrypto does rely on libcrypto.dylib and
libssl.dylib. These methods run without error, but the NSMutableData *data returned
at the end is empty, instead of the decoded data I expected. Any suggestions?
*/

// These methods are part of a Category on NSData

- (NSData *)decodeBase64
{
    return [self decodeBase64WithNewLines:YES];
}

- (NSData *)decodeBase64WithNewLines:(BOOL)encodedWithNewlines
{
    NSAssert1(([self length] <= INT_MAX), @"data length cannot be greater than %d", INT_MAX);
    
    // Create a memory buffer containing Base64 encoded string data
    BIO * mem = BIO_new_mem_buf((void *) [self bytes], (int) [self length]);
    
    // Push a Base64 filter so that reading from the buffer decodes it
    BIO * b64 = BIO_new(BIO_f_base64());
    if (!encodedWithNewlines)
        BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
    mem = BIO_push(b64, mem);
    
    // Decode into an NSMutableData
    NSMutableData * data = [NSMutableData data];
    char inbuf[512];
    int inlen;
    while ((inlen = BIO_read(mem, inbuf, sizeof(inbuf))) > 0)
        [data appendBytes: inbuf length: inlen];
    
    // Clean up and go home
    BIO_free_all(mem);
    return data;
}