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Fix DSA signature algorithm.

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This commit is contained in:
Michael Jumper 2013-12-02 08:47:21 -08:00
parent f1236a9ca1
commit 74e1f57a1d
2 changed files with 40 additions and 3 deletions
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33
src/protocols/ssh/ssh_key.c
View File

@ -168,9 +168,36 @@ int ssh_key_sign(ssh_key* key, const char* data, int length, u_char* sig) {
if (RSA_sign(NID_sha1, digest, dlen, sig, &len, key->rsa) == 1)
return len;
case SSH_KEY_DSA:
if (DSA_sign(NID_sha1, digest, dlen, sig, &len, key->dsa) == 1)
return len;
case SSH_KEY_DSA: {
DSA_SIG* dsa_sig = DSA_do_sign(digest, dlen, key->dsa);
if (dsa_sig != NULL) {
/* Compute size of each half of signature */
int rlen = BN_num_bytes(dsa_sig->r);
int slen = BN_num_bytes(dsa_sig->s);
/* Ensure each number is within the required size */
if (rlen > DSA_SIG_NUMBER_SIZE || slen > DSA_SIG_NUMBER_SIZE)
return -1;
/* Init to all zeroes */
memset(sig, 0, DSA_SIG_SIZE);
/* Add R at the end of the first block of the signature */
BN_bn2bin(dsa_sig->r, sig + DSA_SIG_SIZE
- DSA_SIG_NUMBER_SIZE - rlen);
/* Add S at the end of the second block of the signature */
BN_bn2bin(dsa_sig->s, sig + DSA_SIG_SIZE - slen);
/* Done */
DSA_SIG_free(dsa_sig);
return DSA_SIG_SIZE;
}
}
}

10
src/protocols/ssh/ssh_key.h
View File

@ -54,6 +54,16 @@
*/
#define SSH_DSA_KEY_HEADER "-----BEGIN DSA PRIVATE KEY-----"
/**
* The size of single number within a DSA signature, in bytes.
*/
#define DSA_SIG_NUMBER_SIZE 20
/**
* The size of a DSA signature, in bytes.
*/
#define DSA_SIG_SIZE DSA_SIG_NUMBER_SIZE*2
/**
* The type of an SSH key.
*/