Initial commit

1 files changed, 126 insertions, 0 deletions

diff --git a/base64.c b/base64.c
new file mode 100644
index 0000000..b1d4737
--- /dev/null
+++ b/base64.c
@@ -0,0 +1,126 @@
+#include "base64.h"
+#include <openssl/evp.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+static void remove_lf(char *b64)
+{
+    while ((b64 = strchr(b64, '\n')))
+        memcpy(b64, b64 + 1, strlen(b64));
+}
+
+static size_t base64len(const size_t n)
+{
+    /* Read EVP_EncodeInit(3) for further reference. */
+    return ((n / 48) * 65) + (n % 48 ? 1 + ((n / 3) + 1) * 4 : 0);
+}
+
+static size_t decodedlen(const size_t n)
+{
+    return ((n / 64) * 48) + (n % 64 ? (n / 4) * 3 : 0);
+}
+
+char *base64_encode(const void *const buf, const size_t n)
+{
+    EVP_ENCODE_CTX *const ctx = EVP_ENCODE_CTX_new();
+    char *ret = NULL;
+    unsigned char *b64 = NULL;
+
+    if (!ctx)
+    {
+        fprintf(stderr, "%s: EVP_ENCODE_CTX_new failed\n", __func__);
+        goto end;
+    }
+
+    const size_t b64len = base64len(n);
+
+    if (!(b64 = malloc(b64len + 1)))
+    {
+        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
+        goto end;
+    }
+
+    EVP_EncodeInit(ctx);
+
+    size_t rem = n, done = 0;
+    int outl = b64len;
+
+    while (rem)
+    {
+        const size_t i = n - rem, inl = rem > 48 ? 48 : rem;
+        const unsigned char *const in = buf;
+
+        if (!EVP_EncodeUpdate(ctx, &b64[done], &outl, &in[i], inl))
+        {
+            fprintf(stderr, "%s: EVP_EncodeUpdate failed\n", __func__);
+            goto end;
+        }
+
+        done += outl;
+        rem -= inl;
+    }
+
+    EVP_EncodeFinal(ctx, b64, &outl);
+    ret = (char *)b64;
+    remove_lf(ret);
+
+end:
+    if (!ret)
+        free(b64);
+
+    EVP_ENCODE_CTX_free(ctx);
+    return ret;
+}
+
+void *base64_decode(const char *const b64, size_t *const n)
+{
+    void *ret = NULL;
+    const size_t len = strlen(b64), dlen = decodedlen(len);
+    EVP_ENCODE_CTX *const ctx = EVP_ENCODE_CTX_new();
+    unsigned char *const buf = malloc(dlen);
+
+    if (!buf)
+    {
+        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
+        goto end;
+    }
+    else if (!ctx)
+    {
+        fprintf(stderr, "%s: EVP_ENCODE_CTX_new failed\n", __func__);
+        goto end;
+    }
+
+    EVP_DecodeInit(ctx);
+
+    size_t rem = len, done = 0;
+    int outl = dlen;
+
+    while (rem)
+    {
+        const size_t i = len - rem, inl = rem > 64 ? 64 : rem;
+        const unsigned char *const in = (const unsigned char *)b64;
+
+        if (EVP_DecodeUpdate(ctx, &buf[done], &outl, &in[i], inl) < 0)
+        {
+            fprintf(stderr, "%s: EVP_EncodeUpdate failed\n", __func__);
+            goto end;
+        }
+
+        done += outl;
+        rem -= inl;
+    }
+
+    EVP_DecodeFinal(ctx, buf, &outl);
+    *n = done;
+    ret = buf;
+
+end:
+    if (!ret)
+        free(buf);
+
+    EVP_ENCODE_CTX_free(ctx);
+    return ret;
+}