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Clarify aesgcm-file-encrypt demo #503

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Merged
merged 1 commit into from
May 16, 2025
Merged

Clarify aesgcm-file-encrypt demo #503

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18 changes: 7 additions & 11 deletions crypto/aes/aesgcm-file-encrypt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -340,8 +340,7 @@ int decrypt_file_AesGCM(const char *in_file, const char *out_file,
byte iv[AES_IV_SIZE];
byte wolf_magic[strlen(WOLFCRYPT_MAGIC)];
byte key[AES_KEY_SIZE];
byte tag_dec[AESGCM_TAG_SIZE];
byte tag_enc[AESGCM_TAG_SIZE];
byte tag[AESGCM_TAG_SIZE];
Aes gcm;

if (!in_file || !out_file || !key_str) {
Expand Down Expand Up @@ -396,8 +395,7 @@ int decrypt_file_AesGCM(const char *in_file, const char *out_file,
memset(&gcm, 0, sizeof(Aes));
memset(iv, 0, AES_IV_SIZE);
memset(key, 0, AES_KEY_SIZE);
memset(tag_dec, 0, AESGCM_TAG_SIZE);
memset(tag_enc, 0, AESGCM_TAG_SIZE);
memset(tag, 0, AESGCM_TAG_SIZE);
strncpy((char *)key, key_str, AES_KEY_SIZE);

/* Extract a WOLFCRYPT MAGIC | TAG | IV from the cipher file */
Expand All @@ -412,12 +410,13 @@ int decrypt_file_AesGCM(const char *in_file, const char *out_file,
ret = AES_GCM_AUTH_E;
goto exit;
}
read_size = read(in_fd, tag_enc, AESGCM_TAG_SIZE);
read_size = read(in_fd, tag, AESGCM_TAG_SIZE);
if (read_size != AESGCM_TAG_SIZE) {
perror("read");
ret = -1;
goto exit;
}

read_size = read(in_fd, iv, AES_IV_SIZE);
if (read_size != AES_IV_SIZE) {
perror("read");
Expand All @@ -443,12 +442,9 @@ int decrypt_file_AesGCM(const char *in_file, const char *out_file,
}

if (ret == 0) {
ret = wc_AesGcmEncryptFinal(&gcm, tag_dec, AESGCM_TAG_SIZE);
if (ret == 0 && (memcmp(tag_enc, tag_dec, AESGCM_TAG_SIZE) != 0)) {
perror("TAG didn't match\n");
ret = AES_GCM_AUTH_E;
goto exit;
}
/* The tag param is used to compare to the
calculated tag during decryption */
ret = wc_AesGcmDecryptFinal(&gcm, tag, AESGCM_TAG_SIZE);
}
exit:
free(in_buf);
Expand Down
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