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https://github.com/servalproject/serval-dna.git
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100 lines
3.5 KiB
C
100 lines
3.5 KiB
C
#include "serval.h"
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#include "overlay_address.h"
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#include "crypto.h"
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// verify a signature against a public sas key.
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int crypto_verify_signature(unsigned char *sas_key,
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unsigned char *content, unsigned long long content_len,
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unsigned char *signature_block, unsigned long long signature_len)
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{
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IN();
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if (signature_len!=SIGNATURE_BYTES)
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RETURN(WHY("Invalid signature length"));
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/* reconstitute signed message by putting hash at end of signature */
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unsigned char reassembled[signature_len + content_len];
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bcopy(signature_block, reassembled, signature_len);
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bcopy(content, &reassembled[signature_len], content_len);
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/* verify signature.
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Note that crypto_sign_open requires m to be as large as signature, even
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though it will not need the whole length eventually -- it does use the
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full length and will overwrite the end of a short buffer. */
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unsigned char message[sizeof(reassembled)+64];
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unsigned long long mlen=0;
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int result
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=crypto_sign_edwards25519sha512batch_open(message,&mlen,
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reassembled,sizeof(reassembled),
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sas_key);
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if (result) {
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WHY("Signature verification failed");
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RETURN(-1);
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}
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RETURN(0);
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}
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// verify the signature at the end of a message, on return message_len will be reduced by the length of the signature.
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int crypto_verify_message(struct subscriber *subscriber, unsigned char *message, int *message_len)
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{
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if (!subscriber->sas_valid){
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keyring_send_sas_request(subscriber);
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return WHY("SAS key not currently on record, cannot verify");
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}
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*message_len -= SIGNATURE_BYTES;
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unsigned char hash[crypto_hash_sha512_BYTES];
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crypto_hash_sha512(hash,message,*message_len);
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return crypto_verify_signature(subscriber->sas_public, hash,
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crypto_hash_sha512_BYTES, &message[*message_len], SIGNATURE_BYTES);
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}
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// generate a signature for this raw content, copy the signature to the address requested.
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int crypto_create_signature(unsigned char *key,
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unsigned char *content, unsigned long long content_len,
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unsigned char *signature, unsigned long long *sig_length)
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{
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IN();
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if (*sig_length < SIGNATURE_BYTES)
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RETURN(WHY("Not enough space to store signature"));
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unsigned char sig[content_len + SIGNATURE_BYTES];
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/* Why does this primitive copy the whole input message? We don't want that message format, it just seems like a waste of effor to me. */
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unsigned long long length = 0;
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crypto_sign_edwards25519sha512batch(sig,&length,
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content,content_len,
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key);
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if (length != sizeof(sig))
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RETURN(WHYF("Signing seems to have failed (%d, expected %d)",length,sizeof(sig)));
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bcopy(sig, signature, SIGNATURE_BYTES);
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*sig_length=SIGNATURE_BYTES;
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RETURN(0);
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}
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// sign the hash of a message, adding the signature to the end of the message buffer.
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int crypto_sign_message(struct subscriber *source, unsigned char *content, int buffer_len, int *content_len)
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{
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if (*content_len + SIGNATURE_BYTES > buffer_len)
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return WHYF("Insufficient space in message buffer to add signature. %d, need %d",buffer_len, *content_len + SIGNATURE_BYTES);
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unsigned char *key=keyring_find_sas_private(keyring, source->sid, NULL);
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if (!key)
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return WHY("Could not find signing key");
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unsigned char hash[crypto_hash_sha512_BYTES];
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crypto_hash_sha512(hash, content, *content_len);
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unsigned long long sig_length = SIGNATURE_BYTES;
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int ret=crypto_create_signature(key, hash, crypto_hash_sha512_BYTES, &content[*content_len], &sig_length);
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*content_len+=sig_length;
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return ret;
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}
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