stupidgcm: introduce stupidAEADCommon and use for both chacha & gcm

Nice deduplication and brings the GCM decrypt speed up to par.

internal/speed$ benchstat old new
name                old time/op   new time/op   delta
StupidGCM-4          4.71µs ± 0%   4.66µs ± 0%   -0.99%  (p=0.008 n=5+5)
StupidGCMDecrypt-4   5.77µs ± 1%   4.51µs ± 0%  -21.80%  (p=0.008 n=5+5)

name                old speed     new speed     delta
StupidGCM-4         870MB/s ± 0%  879MB/s ± 0%   +1.01%  (p=0.008 n=5+5)
StupidGCMDecrypt-4  710MB/s ± 1%  908MB/s ± 0%  +27.87%  (p=0.008 n=5+5)

1 files changed, 0 insertions, 194 deletions

diff --git a/internal/stupidgcm/chacha.c b/internal/stupidgcm/chacha.c
deleted file mode 100644
index 05d68af..0000000
--- a/internal/stupidgcm/chacha.c
+++ /dev/null
@@ -1,194 +0,0 @@
-#include "chacha.h"
-#include <openssl/evp.h>
-#include <stdio.h>
-//#cgo pkg-config: libcrypto
-
-static void panic(const char* const msg)
-{
-    fprintf(stderr, "panic in C code: %s\n", msg);
-    __builtin_trap();
-}
-
-static const EVP_CIPHER* getEvpCipher(enum aeadType cipherId)
-{
-    switch (cipherId) {
-    case aeadTypeChacha:
-        return EVP_chacha20_poly1305();
-    case aeadTypeGcm:
-        return EVP_aes_256_gcm();
-    }
-    panic("unknown cipherId");
-    return NULL;
-}
-
-// We only support 16-byte tags
-static const int supportedTagLen = 16;
-
-// https://wiki.openssl.org/index.php/EVP_Authenticated_Encryption_and_Decryption#Authenticated_Encryption_using_GCM_mode
-int aead_seal(
-    const enum aeadType cipherId,
-    const unsigned char* const plaintext,
-    const int plaintextLen,
-    const unsigned char* const authData,
-    const int authDataLen,
-    const unsigned char* const key,
-    const int keyLen,
-    const unsigned char* const iv,
-    const int ivLen,
-    unsigned char* const ciphertext,
-    const int ciphertextBufLen)
-{
-    const EVP_CIPHER* evpCipher = getEvpCipher(cipherId);
-
-    // Create scratch space "ctx"
-    EVP_CIPHER_CTX* ctx = EVP_CIPHER_CTX_new();
-    if (!ctx) {
-        panic("EVP_CIPHER_CTX_new failed");
-    }
-
-    // Set cipher
-    if (EVP_EncryptInit_ex(ctx, evpCipher, NULL, NULL, NULL) != 1) {
-        panic("EVP_EncryptInit_ex set cipher failed");
-    }
-
-    // Check keyLen by trying to set it (fails if keyLen != 32)
-    if (EVP_CIPHER_CTX_set_key_length(ctx, keyLen) != 1) {
-        panic("keyLen mismatch");
-    }
-
-    // Set IV length so we do not depend on the default
-    if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivLen, NULL) != 1) {
-        panic("EVP_CTRL_AEAD_SET_IVLEN failed");
-    }
-
-    // Set key and IV
-    if (EVP_EncryptInit_ex(ctx, NULL, NULL, key, iv) != 1) {
-        panic("EVP_EncryptInit_ex set key & iv failed");
-    }
-
-    // Provide authentication data
-    int outLen = 0;
-    if (EVP_EncryptUpdate(ctx, NULL, &outLen, authData, authDataLen) != 1) {
-        panic("EVP_EncryptUpdate authData failed");
-    }
-    if (outLen != authDataLen) {
-        panic("EVP_EncryptUpdate authData: unexpected length");
-    }
-
-    // Encrypt "plaintext" into "ciphertext"
-    if (plaintextLen > ciphertextBufLen) {
-        panic("plaintext overflows output buffer");
-    }
-    if (EVP_EncryptUpdate(ctx, ciphertext, &outLen, plaintext, plaintextLen) != 1) {
-        panic("EVP_EncryptUpdate ciphertext failed");
-    }
-    if (outLen != plaintextLen) {
-        panic("EVP_EncryptUpdate ciphertext: unexpected length");
-    }
-    int ciphertextLen = outLen;
-
-    // Finalise encryption
-    // Normally ciphertext bytes may be written at this stage, but this does not occur in GCM mode
-    if (EVP_EncryptFinal_ex(ctx, ciphertext + plaintextLen, &outLen) != 1) {
-        panic("EVP_EncryptFinal_ex failed");
-    }
-    if (outLen != 0) {
-        panic("EVP_EncryptFinal_ex: unexpected length");
-    }
-
-    // Get MAC tag and append it to the ciphertext
-    if (ciphertextLen + supportedTagLen > ciphertextBufLen) {
-        panic("tag overflows output buffer");
-    }
-    if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, supportedTagLen, ciphertext + plaintextLen) != 1) {
-        panic("EVP_CTRL_AEAD_GET_TAG failed");
-    }
-    ciphertextLen += supportedTagLen;
-
-    // Free scratch space
-    EVP_CIPHER_CTX_free(ctx);
-
-    return ciphertextLen;
-}
-
-int aead_open(
-    const enum aeadType cipherId,
-    const unsigned char* const ciphertext,
-    const int ciphertextLen,
-    const unsigned char* const authData,
-    const int authDataLen,
-    unsigned char* const tag,
-    const int tagLen,
-    const unsigned char* const key,
-    const int keyLen,
-    const unsigned char* const iv,
-    const int ivLen,
-    unsigned char* const plaintext,
-    const int plaintextBufLen)
-{
-    const EVP_CIPHER* evpCipher = getEvpCipher(cipherId);
-
-    // Create scratch space "ctx"
-    EVP_CIPHER_CTX* ctx = EVP_CIPHER_CTX_new();
-    if (!ctx) {
-        panic("EVP_CIPHER_CTX_new failed");
-    }
-
-    // Set cipher
-    if (EVP_DecryptInit_ex(ctx, evpCipher, NULL, NULL, NULL) != 1) {
-        panic("EVP_DecryptInit_ex set cipher failed");
-    }
-
-    // Check keyLen by trying to set it (fails if keyLen != 32)
-    if (EVP_CIPHER_CTX_set_key_length(ctx, keyLen) != 1) {
-        panic("keyLen mismatch");
-    }
-
-    // Set IV length so we do not depend on the default
-    if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivLen, NULL) != 1) {
-        panic("EVP_CTRL_AEAD_SET_IVLEN failed");
-    }
-
-    // Set key and IV
-    if (EVP_DecryptInit_ex(ctx, NULL, NULL, key, iv) != 1) {
-        panic("EVP_DecryptInit_ex set key & iv failed");
-    }
-
-    // Provide authentication data
-    int outLen = 0;
-    if (EVP_DecryptUpdate(ctx, NULL, &outLen, authData, authDataLen) != 1) {
-        panic("EVP_DecryptUpdate authData failed");
-    }
-    if (outLen != authDataLen) {
-        panic("EVP_DecryptUpdate authData: unexpected length");
-    }
-
-    // Decrypt "ciphertext" into "plaintext"
-    if (ciphertextLen > plaintextBufLen) {
-        panic("ciphertextLen overflows output buffer");
-    }
-    if (EVP_DecryptUpdate(ctx, plaintext, &outLen, ciphertext, ciphertextLen) != 1) {
-        panic("EVP_DecryptUpdate failed");
-    }
-    int plaintextLen = outLen;
-
-    // Check tag
-    if (tagLen != supportedTagLen) {
-        panic("unsupported tag length");
-    }
-    if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, tagLen, tag) != 1) {
-        panic("EVP_CTRL_AEAD_SET_TAG failed");
-    }
-    if (EVP_DecryptFinal_ex(ctx, plaintext + plaintextLen, &outLen) != 1) {
-        // authentication failed
-        return -1;
-    }
-    if (outLen != 0) {
-        panic("EVP_EncryptFinal_ex: unexpected length");
-    }
-
-    /* Clean up */
-    EVP_CIPHER_CTX_free(ctx);
-
-    return plaintextLen;
-}